carbon footprint of commercial air travel

Climate change and flying: what share of global CO2 emissions come from aviation?

Aviation accounts for around 2.5% of global co₂ emissions, but 3.5% when we take non-co₂ impacts on climate into account..

Flying is a highly controversial topic in climate debates. There are a few reasons for this.

The first is the disconnect between its role in our personal and collective carbon emissions. Air travel dominates a frequent traveller's individual contribution to climate change. Yet aviation overall accounts for only 2.5% of global carbon dioxide (CO 2 ) emissions. This is because there are large inequalities in how much people fly – many do not, or cannot afford to, fly at all. 1

The second is how aviation emissions are attributed to countries. CO 2 emissions from domestic flights are counted in a country’s emission accounts. International flights are not – instead they are counted as their own category: ‘bunker fuels’. The fact that they don’t count towards the emissions of any country means there are few incentives for countries to reduce them.

It’s also important to note that unlike the most common greenhouse gases – carbon dioxide, methane or nitrous oxide – non-CO 2 forcings from aviation are not included in the Paris Agreement. This means they could be easily overlooked – especially since international aviation is not counted within any country’s emissions inventories or targets.

How much of a role does aviation play in global emissions and climate change? In this article we take a look at the key numbers that are useful to know.

Global aviation (including domestic and international; passenger and freight) accounts for:

• 1.9% of greenhouse gas emissions (which includes all greenhouse gases, not only CO 2 )
• 2.5% of CO 2 emissions
• 3.5% of 'effective radiative forcing' – a closer measure of its impact on warming.

The latter two numbers refer to 2018, and the first to 2016, the latest year for which such data are available.

Aviation accounts for 2.5% of global CO 2 emissions

As we will see later in this article, there are a number of processes by which aviation contributes to climate change. But the one that gets the most attention is its contribution via CO 2 emissions. Most flights are powered by jet gasoline – although some partially run on biofuels – which is converted to CO 2 when burned.

In a recent paper, researchers – David Lee and colleagues – reconstructed annual CO 2 emissions from global aviation dating back to 1940. 2 This was calculated based on fuel consumption data from the International Energy Agency (IEA), and earlier estimates from Robert Sausen and Ulrich Schumann (2000). 3

The time series of global emissions from aviation since 1940 is shown in the accompanying chart. In 2018, it’s estimated that global aviation – which includes both passenger and freight – emitted 1.04 billion tonnes of CO 2 .

This represented 2.5% of total CO 2 emissions in 2018. 4 , 5

Aviation emissions have doubled since the mid-1980s. But, they’ve been growing at a similar rate as total CO 2 emissions – this means its share of global emissions has been relatively stable: in the range of 2% to 2.5%. 6

Non-CO 2 climate impacts mean aviation accounts for 3.5% of global warming

Aviation accounts for around 2.5% of global CO 2 emissions, but it’s overall contribution to climate change is higher. This is because air travel does not only emit CO 2 : it affects the climate in a number of more complex ways.

As well as emitting CO 2 from burning fuel, planes affect the concentration of other gases and pollutants in the atmosphere. They result in a short-term increase, but long-term decrease in ozone (O 3 ); a decrease in methane (CH 4 ); emissions of water vapour; soot; sulfur aerosols; and water contrails. While some of these impacts result in warming, others induce a cooling effect. Overall, the warming effect is stronger.

David Lee et al. (2020) quantified the overall effect of aviation on global warming when all of these impacts were included. 2 To do this they calculated the so-called ‘Radiative Forcing’. Radiative forcing measures the difference between incoming energy and the energy radiated back to space. If more energy is absorbed than radiated, the atmosphere becomes warmer.

In their chart we see their estimates for the radiative forcing of the different elements. When we combine them, aviation accounts for approximately 3.5% of effective radiative forcing: that is, 3.5% of warming.

Although CO 2  gets most of the attention, it accounts for less than half of this warming. Two-thirds (66%) comes from non-CO 2 forcings. Contrails – water vapor trails from aircraft exhausts – account for the largest share.

We don’t yet have the technologies to decarbonize air travel

Aviation’s contribution to climate change – 3.5% of warming, or 2.5% of CO 2 emissions – is often less than people think. It’s currently a relatively small chunk of emissions compared to other sectors.

The key challenge is that it is particularly hard to decarbonize. We have solutions to reduce emissions for many of the largest emitters – such as power or road transport – and it’s now a matter of scaling them. We can deploy renewable and nuclear energy technologies, and transition to electric cars. But we don’t have proven solutions to tackle aviation yet.

There are some design concepts emerging – Airbus, for example, have announced plans to have the first zero-emission aircraft by 2035, using hydrogen fuel cells. Electric planes may be a viable concept, but are likely to be limited to very small aircraft due to the limitations of battery technologies and capacity.

Innovative solutions may be on the horizon, but they’re likely to be far in the distance.

Appendix: Efficiency improvements means air traffic has increased more rapidly than emissions

Global emissions from aviation have increased a lot over the past half-century. However, air travel volumes increased even more rapidly.

Since 1960, aviation emissions increased almost seven-fold; since 1970 they’ve tripled. Air traffic volume – here defined as revenue passenger kilometers (RPK) traveled – increased by orders of magnitude more : almost 300-fold since 1950; and 75-fold since 1960. 7

The much slower growth in emissions means aviation efficiency has seen massive improvements. In the chart we show both the increase in global airline traffic since 1950, and aviation efficiency, measured as the quantity of CO 2 emitted per revenue passenger kilometer traveled. In 2018, approximately 125 grams of CO 2  were emitted per RPK. In 1960, this was eleven-fold higher; in 1950 it was twenty-fold higher. Aviation has seen massive efficiency improvements over the past 50 years.

These improvements have come from several sources: improvements in the design and technology of aircraft; larger aircraft sizes (allowing for more passengers per flight); and an increase in how ‘full’ passenger flights are. This last metric is termed the ‘passenger load factor’. The passenger load factor measures the actual number of kilometers traveled by paying customers (RPK) as a percentage of the available seat kilometers (ASK) – the kilometers traveled if every plane was full. If every plane was full the passenger load factor would be 100%. If only three-quarters of the seats were filled, it would be 75%.

The global passenger load factor increased from 61% in 1950 to 82% in 2018 .

The best estimates put this figure at around 80% of the world population. We look at this in more detail in our article " Where in the world do people have the highest CO2 emissions from flying? "

Lee, D. S., Fahey, D. W., Skowron, A., Allen, M. R., Burkhardt, U., Chen, Q., ... & Gettelman, A. (2020). The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018 . Atmospheric Environment , 117834.

Sausen, R., & Schumann, U. (2000). Estimates of the climate response to aircraft CO2 and NOx emissions scenarios . Climatic Change , 44 (1-2), 27-58.

The Global Carbon Budget estimated total CO 2 emissions from all fossil fuels, cement production and land-use change to be 42.1 billion tonnes in 2018. This means aviation accounted for [1 / 42.1 * 100] = 2.5% of total emissions.

Global Carbon Project. (2019). Supplemental data of Global Carbon Budget 2019 (Version 1.0) [Data set]. Global Carbon Project. https://doi.org/10.18160/gcp-2019 .

If we were to exclude land use change emissions, aviation accounted for 2.8% of fossil fuel emissions. The Global Carbon Budget estimated total CO 2 emissions from fossil fuels and cement production to be 36.6 billion tonnes in 2018. This means aviation accounted for [1 / 36.6 * 100] = 2.8% of total emissions.

2.3% to 2.8% of emissions if land use is excluded.

Airline traffic data comes from the International Civil Aviation Organization (ICAO) via Airlines for America . Revenue passenger kilometers (RPK) measures the number of paying passengers multiplied by their distance traveled.

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How your flight emits as much CO2 as many people do in a year

Even short-haul flights produce huge amounts of CO2, figures show

Taking a long-haul flight generates more carbon emissions than the average person in dozens of countries around the world produces in a whole year, a new Guardian analysis has found.

The figures highlight the disproportionate carbon footprint of those who can afford to fly, with even a short-haul return flight from London to Edinburgh contributing more CO2 than the mean annual emissions of a person in Uganda or Somalia.

2019 is forecast to be another record-breaking year for air travel, with passengers expected to fly a total of 8.1tn km, up 5% from last year and more than 300% since 1990.

Taking one return flight generates more CO2 than citizens of some countries produce in a year

How about your next trip.

According to figures from German nonprofit Atmosfair, flying from London to New York and back generates about 986kg of CO2 per passenger. There are 56 countries where the average person emits less carbon dioxide in a whole year – from Burundi in Africa to Paraguay in South America.

But even a relatively short return trip from London to Rome carries a carbon footprint of 234kg of CO2 per passenger – more than the average produced by citizens of 17 countries annually.

The figures are averages taking into account which aircraft models are typically used on flight routes, and the estimated occupancy of seats on board those planes. The figures include only the CO2 generated by burning jet fuel, not any emissions embedded in the construction of the plane or any other greenhouse gases that might be produced, such as water vapour.

Aviation emissions could triple in the next three decades

The aviation sector currently accounts for about 2% of global emissions, and is one of the fastest-growing polluters.

According to projections from researchers at Manchester Metropolitan University, emissions from the sector could more than double by 2050 even if planes become substantially more fuel-efficient and airlines save additional carbon by optimising their operations.

Under a less optimistic scenario, a lower level of fuel savings could lead emissions to triple by 2050.

“The increase in traffic has historically outpaced the improvements in technology,” says Dr John Broderick, who researches climate policy and international transport at the University of Manchester.

How can the aviation industry’s climate impact be regulated?

The International Civil Aviation Organization (ICAO) – the UN body responsible for limiting the carbon footprint from international air travel – is introducing a scheme aiming to offset emissions by allowing airlines to purchase carbon credits rather than burn less fossil fuels.

Broderick is sceptical of the scheme’s benefits. “You still have a plan to increase the size of the industry … at a time when we should be making substantial reductions in emissions, particularly from the rich parts of the world.”

When asked for comment for this story, the ICAO described it as “meaningless cherry-picking of unrelated data points”.

In 2019, almost 40m flights are expected to depart from airports worldwide – more than 100,000 trips per day.

Tim Alderslade, chief executive of Airlines UK, the industry association representing 13 UK carriers, said: “Airlines believe we need a strategy that meets the government’s ambition of promoting sustainable growth for our sector. Aviation has to earn the right to expand and that’s why we’re committed to halving our emissions by 2050, and working with national governments to agree an ambitious plan that can deliver a zero-carbon future.”

Environmental groups are calling on policymakers to constrain the total number of flights and limit further expansion of airports.

Policy proposals include a “frequent flyers’ levy” which would increase progressively with every flight a person takes in a year while minimising the impact on those who fly only occasionally.

“We don’t want to penalise hardworking families that perhaps travel abroad once a year for a holiday,” says Mike Childs, head of science, policy and research at Friends of the Earth UK.

Childs cited a 2014 survey by the Department for Transport which revealed that 15% of the UK’s population took 70% of flights.

“We need to recognise that aviation is a luxury and we need to share that luxury fairly.”

Credit and data sources

Emissions data for flight connections was sourced from atmosfair.de and takes into account factors such as the fuel efficiency of different plane models and the average passenger load factor in different regions of the world.

The emissions estimates given in this article represent averages across all aircraft types serving a given route. Individual airlines might operate more or less carbon efficient planes.

The Guardian’s interactive calculator covers the world’s 100 busiest airports and selected UK airports.

Global flight path data was sourced from flightradar24.com and excludes aircraft that do not share location data with Flightradar’s network of receivers.

Emissions projections were provided by Prof David Lee at Manchester Metropolitan University and are based on work by Fleming and Ziegler in ICAO’s 2016 environmental report.

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‘Worse Than Anyone Expected’: Air Travel Emissions Vastly Outpace Predictions

The findings put pressure on airline regulators to take stronger action to fight climate change as they prepare for a summit next week.

By Hiroko Tabuchi

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Greenhouse gas emissions from commercial air travel are growing at a faster clip than predicted in previous, already dire, projections , according to new research — putting pressure on airline regulators to take stronger action as they prepare for a summit next week.

The United Nations aviation body forecasts that airplane emissions of carbon dioxide , a major greenhouse gas, will reach just over 900 million metric tons in 2018, and then triple by 2050.

But the new research, from the International Council on Clean Transportation , found that emissions from global air travel may be increasing more than 1.5 times as fast as the U.N. estimate. The researchers analyzed nearly 40 million flights around the world last year.

“Airlines, for all intents and purposes, are becoming more fuel efficient. But we’re seeing demand outstrip any of that,” said Brandon Graver , who led the new study. “The climate challenge for aviation is worse than anyone expected.”

Airlines in recent years have invested in lighter, more fuel-efficient aircraft, and have explored powering their planes with biofuel.

Over all, air travel accounts for about 2.5 percent of global carbon dioxide emissions — a far smaller share than emissions from passenger cars or power plants. Still, one study found that the rapid growth in plane emissions could mean that by 2050, aviation could take up a quarter of the world’s “carbon budget ,” or the amount of carbon dioxide emissions permitted to keep global temperature rise to within 1.5 degrees Celsius above preindustrial levels.

The decision by Greta Thunberg, a young climate activist, to sail across the Atlantic rather than travel by air ahead of her speech at the United Nations next week, has refocused attention on aviation’s role in causing climate change and its consequences, including sea-level rise and more intense heat waves, hurricanes, flooding and drought.

Climate protesters have said they plan to gather in Montreal next week, where airline regulators are set to hold their own summit.

William Raillant-Clark , a spokesman for the U.N. aviation body, stood by its emissions projection , which he said was “the most up-to-date” and provided “a clear picture on the future environmental trends.” He added that the group “endorses and welcomes wholeheartedly” calls for the aviation industry to address climate change with greater urgency.

Underlying the growth in aviation emissions is the rapid expansion of air travel worldwide, propelled by a proliferation of low-cost airlines and a booming tourism industry catering to a growing middle class.

A separate study released this week by the industry group Airports Council International found that the world’s fastest-growing airports were in emerging economies; 12 of the top 30 were in either China or India.

Still, the new data from the clean transportation council found that flights from airports in the United States were responsible for almost one quarter of global passenger flight-related carbon dioxide emissions. China was the next biggest source of passenger aviation emissions, followed by the United Kingdom, Japan and Germany ; the lowest-income countries that contain half the world’s population accounted for only 10 percent of all emissions.

The study underscored the heavy carbon-dioxide footprint of domestic flights, often left out of negotiations over global emissions-reduction targets. Domestic travel accounted for a large majority of departures in countries including the United States, China, Indonesia, Brazil and Australia.

Governments have pledged to take major steps to improve fuel economy in their routes and fleets. Under a plan adopted by the U.N. body, the International Civil Aviation Organization , three years ago, airlines will start to voluntarily offset most of the growth in their carbon dioxide emissions beginning in 2020. Carbon offsets compensate for emissions by canceling out greenhouse gas emissions elsewhere in the world. (For example, the offset may involve paying for renewable energy or other programs designed to reduce emissions.)

Some governments have suggested going further. In Germany, the Green Party has suggested banning domestic air travel altogether to force Germans to travel by train, which pollutes less.

“At a time when students are going on climate strikes around the world, this will really put pressure on the aviation industry to be much more ambitious,” said Annie Petsonk, international counsel for the Environmental Defense Fund. “They’re beginning to understand that for most people who fly, aviation is the biggest part of their personal carbon footprint.”

For more news on climate and the environment, follow @NYTClimate on Twitter .

An earlier version of this article misstated the nature of a global aviation summit meeting in Montreal next week. While industry representatives will be present as observers, the meeting is for airline regulators and diplomatic delegations, not executives.

How we handle corrections

Hiroko Tabuchi is a climate reporter. She joined The Times in 2008, and was part of the team awarded the 2013 Pulitzer Prize for Explanatory Reporting. She previously wrote about Japanese economics, business and technology from Tokyo. More about Hiroko Tabuchi

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How airlines can chart a path to zero-carbon flying

The airline industry is understandably focused on the coronavirus pandemic’s impact on growth, along with the health and livelihoods of its millions of workers.

This year now represents the biggest retrenchment in the history of aviation, with airline capacity down roughly 75 percent as of early April. That means an industry with a predictably steady growth rate has suddenly shrunk to a fraction of its size. It is unclear how protracted the decline will be, though demand is likely to bottom out in 2020 before returning to pre-crisis levels several years from now. The timing will depend on many factors outside the industry’s control.

In the longer term, aviation is likely to undergo structural changes with regard to demand and the degree of industry consolidation, along with unprecedented government support. That transition provides an opportunity to rebuild the industry for a low-carbon future, something that airlines have been grappling with for some time.

Even before the coronavirus pandemic began, the industry was facing the challenge of reducing its carbon emissions in line with international goals to reach net-zero emissions by 2050. Forces that have buoyed the case for sustainability—including customers and regulators worried about emissions and unpredictable future carbon policies—have shifted with the pandemic, as airlines’ survival seems to be at stake.

The industry has a solid record on fuel efficiency: fuel burn per passenger-kilometer has dropped by half since 1990, according to the International Air Transport Association. The current crisis could provide forward-thinking airlines with a chance to emphasize their fuel-efficiency programs and justify the retirement of older, less-fuel-efficient aircraft (see sidebar, “ Ten questions airline executives should be asking ”). Modernizing fleets and improving operational efficiency are important; however, in the best case, annual industry growth counters the emissions that they save. Carbon offsetting holds more promise, and it can help serve as a bridge while the industry takes action needed to reduce its own emissions over time.

The option that could be transformative, aligning the industry’s growth ambitions with Paris Agreement targets, is sustainable aviation fuel (SAF). Compared with fossil kerosene, SAF could mean a reduction in carbon emissions of 70 percent to almost 100 percent. While SAF has drawbacks, including high prices and supply concerns, airline CEOs should view it as a promising tool in their decarbonization tool kits. To help push options forward, airlines can make targeted investments and purchase commitments that would increase SAF use (currently at less than 1 percent of total consumed jet fuel) while reducing costs.

Because of the scale of the challenge, any solution will require a multistakeholder approach that also includes governments, tech players, and suppliers. The trick is to create a suitable regulatory framework and supporting incentives so that no single player is penalized for going it alone.

The case for action

The aviation industry has taken steps to address rising emissions. In 2009, it set ambitious targets that include carbon-neutral growth from 2020 onward and halving its net emissions from 2005 levels by 2050.

We don’t know what the pandemic will mean for emissions growth over time. But the target for all industries, companies, and countries is to reach net-zero carbon emissions by 2050, as laid out in the Intergovernmental Panel on Climate Change goals of limiting global warming to no more than 1.5°C above preindustrial levels. As the energy and transportation industries create a path to decarbonize, sectors in which climate effects are hard to abate are coming under more pressure, and aviation is no exception. McKinsey recently developed a set of 1.5°C scenarios  that would see reductions in aviation emissions of 18 to 35 percent compared with a business-as-usual pathway by 2030. 1 The scenarios include assumptions about improvements in energy efficiency (driven by operational improvements and fleet modifications), the share of zero-emission sustainable aviation fuel in the fuel mix, and reduced travel demand and modal shifts. 2016 was the baseline used for all scenarios, and the business-as-usual outlook is based on McKinsey’s 2019 Global Energy Perspective.

Nations excluded aviation and international shipping when setting carbon targets because emissions are difficult to allocate to a particular country. But airlines shouldn’t risk the perception that they aren’t doing enough about CO 2 , especially amid mounting scrutiny from the flying public, the media, investors, and regulators. With half of industry growth coming from Asia, including China, India, and Southeast Asia, decarbonization can work only if airlines from those nations are on board.

Despite the convenience of flying, consumers have said they are increasingly worried about the impact it has on climate change. Public movements, such as #flygskam (“flight shaming”) and Fridays for Future, reflect this sentiment, particularly among millennials.

Investors, for their part, are concerned about the effects of climate risk on airline valuations, with climate-related financial disclosures becoming more common. The frequency of climate-related discussions in European earnings calls with investors increased nearly sevenfold since 2017, according to HSBC data. At the same time, corporate customers turn to airlines for ways to reduce scope-3 emissions 2 Scope-3 emissions are all indirect emissions that occur in the value chain of a reporting company. For an airline, they would include the emissions involved in manufacturing the plane and in preparing the food that people eat in flight, for example. incurred from their employees’ business travel.

Institutions and governments are announcing policies on CO 2 or SAF. Norway has mandated that 0.5 percent of aviation fuel in the country must be sustainable this year, growing to 30 percent by 2030. It wants all short-haul flights to be 100 percent electric by 2040. And Canada implemented a carbon tax of 30 Canadian dollars (around $21) per metric ton of CO 2 in most of its regions, based on the amount of loaded fuel for domestic travel.

Much of the pressure is rooted in consumer unease. Last summer, McKinsey conducted a survey of roughly 5,300 fliers in 13 aviation markets to get their views on flying and climate change. Although the survey took place well before the coronavirus essentially shut down air travel, more than 50 percent of respondents said they were “really worried” about climate change. Those feelings were higher among women than men and most pronounced among people aged 34 and younger, suggesting that these perceptions aren’t going away (Exhibit 1).

Roughly a third of respondents said they were planning to reduce their air travel because of climate concerns (Exhibit 2), and most respondents said they were willing to pay somewhat more for carbon-neutral tickets, with fliers aged 18 to 34 willing to pay the most. At the same time, respondents felt that airlines and government subsidies should cover the costs before corporate customers or fliers themselves did. When asked about feasible ways to decarbonize aviation, they ranked carbon offsetting as the least appropriate option.

In the short term, the coronavirus pandemic and the resulting demand shock have reduced carbon emissions. We don’t know what the aviation industry will look like after the coronavirus pandemic, but we believe that customer preferences for environmental flying will continue.

Tech and efficiency gains

Airlines are already working to align emissions cuts with their bottom-line interests. They have encouraged operational efficiency and optimal air-traffic management (ATM) and invested billions of dollars to modernize aircraft with more efficient aerodynamics and engines using lighter-weight materials. However, these actions get the industry only so far, cutting emissions by no more than 20 to 30 percent compared with the do-nothing alternative.

Operational efficiency

Fuel typically accounts for 20 to 30 percent of operational costs—one of the largest single cost items. Every kilogram of kerosene produces 3.15 kilograms of CO 2 . 3 “Aviation Carbon Offset Programme: Frequently asked questions,” International Air Transport Association, April 30, 2020, iata.org. Airlines therefore have an intrinsic motivation for adopting more fuel-efficient flying, taxiing, and airport operations. They are also eking out fuel-efficiency gains by decreasing the extra fuel loaded onto aircraft and introducing lighter materials to reduce aircraft weight.

In a recent survey of airlines, we learned that, despite these efficiency gains, carriers capture only around 50 percent of their full potential. Only a few airlines address their employees’ behaviors and mindsets related to fuel. This is a crucial area, since pilots, dispatchers, and other airline employees have considerable discretion in preparing and conducting safe flights, with direct implications for fuel consumption.

To increase fuel efficiency, airlines should identify the areas needing improvement with the help of analytics and systematically drive behavioral change with their frontline employees. For example, in a behavioral-science project , Virgin Atlantic Airways successfully demonstrated how nudging , or using subtle interventions to change behavior, can make pilots use less fuel.

The airline randomly placed all 335 of its pilots into four groups. It informed the members of one group (the control group) that they were part of a fuel-use study, with no further information. It provided the experimental groups with feedback on their fuel use, including monthly assessments on fuel loading, optimized flying, and efficient taxiing. According to the researchers, all three experimental groups saved more fuel than the control group did, and pilots in the “prosocial” group—those told that the company would make a charitable donation if they reached their targets—reported the highest level of job satisfaction.

Airlines also consume additional fuel from zigzagging through nations’ ATM sectors that require predefined handovers. Other inefficiencies include limits on air-traffic-control capacity and a lack of automation in air-navigation services. Eliminating those inefficiencies requires a joint effort from a large group of stakeholders, including governments, regulators, and militaries, which makes the process painfully slow.

New aircraft technology

Airlines invested almost $120 billion in new aircraft in 2018 alone, according to Teal data. New models have highly efficient engines, and modern long-haul twin-engine aircraft are replacing four-engine aircraft, which enables up to 20 percent fuel-efficiency improvement per passenger.

Regarding commercial-fleet strategy, executives should consider not just fuel-price predictions but also the future cost of carbon. Applying carbon emissions as a fuel-cost premium could lead to an accelerated fleet rollover and faster adaption of future aircraft technology, including some electrification.

Alternative propulsion (such as via electricity and hydrogen) could one day replace conventional turbine-powered planes, especially smaller aircraft on shorter flights. However, the use of fully electric aircraft carrying more than 100 passengers appears unlikely within the next 30 years or longer. Given the lower energy density of batteries compared to fuels, aircraft would need to carry more than 50 kilograms of battery weight (with today’s technology) to replace one kilogram of kerosene. Because battery weight wouldn’t burn off the way fuel does, carrying that weight for an entire flight would require energy, creating a penalty for longer flights in particular.

Electric propulsion could start with hybrid- or turboelectric flying, enabling further improvements in fuel efficiency as jet engines become smaller and lighter, using less fuel. For example, Ampaire, a Los Angeles–based start-up, is working with Mokulele Airlines, an interisland carrier in Hawaii, on hybrid-electric flights for aircraft with around ten passengers.

Aircraft could also be powered by hydrogen, either from direct combustion (hydrogen turbine) or via a fuel cell. Hydrogen emits no CO 2 during the combustion process and allows for significant reduction of other elements that drive global warming, such as soot, nitrogen oxides, and high-altitude water vapor. (Hydrogen can also be a feedstock for SAF; more on that in a later section.)

However, liquified hydrogen would require four times the volume of kerosene, so its use would reduce space for customers or cargo. Also, airports would need new parallel refueling infrastructures, including fuel trucks able to store liquified hydrogen. Refueling time would grow for longer-range aircraft, affecting gate and aircraft utilization. Smaller aircraft powered with hydrogen could become feasible in the next decade. For aircraft with more than approximately 100 passengers, significant aircraft-technology development would be required, and infrastructure constraints would need to be overcome.

Intermodal shift

Trains and buses generate less CO 2 on a per-passenger basis than planes do (and rail freight can be a lower-emission alternative for air cargo). Airlines can work with rail and bus companies to offer a more integrated service for short connections and when alternative means of transport are available. Examples abound, often in Europe, such as the rail link between the United Kingdom and Europe that cut back the need for flying. But carbon savings here don’t make a large dent in overall airline emissions, 4 McKinsey analysis shows that only 4 percent of worldwide emissions result from flights of fewer than 500 kilometers; 13 percent are from flights of fewer than 1,000 kilometers. nor are they a great option for airlines’ bottom lines.

Carbon offsetting

Carbon offsetting, or CO 2 compensation, provides a large-scale and industry-agnostic means of compensating for CO 2 emissions by reducing emissions elsewhere. Airlines are on board with offsetting; indeed, the industry is expected to be a key sponsor for global reforestation. Offsetting is also the basis for such market-based measures as Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), the International Civil Aviation Organization’s carbon-reduction initiative.

Offsetting allows worldwide investment in projects to compensate for emissions, independent of buyers’ own efforts to reduce their footprints. Planting trees and letting them grow to capture CO 2 can cost as low as $5 to $10 per metric ton of CO 2 captured. That translates into a ticket-price increase of less than $1 per passenger on a short-haul flight. Besides nature-based solutions such as planting trees, offsetting projects can be related to resource recovery (such as methane capture from landfills), renewable energy, energy efficiency, and fuel switching, among other areas.

Yet offsetting as a longer-term solution is controversial. Some critics view it as an attempt at greenwashing. Many also worry that offsetting might relieve the pressure on buyers to reduce their emissions in other ways: they might feel better by offsetting and not consider enacting other emission-cutting measures. A credible environmental-footprint strategy includes reducing emissions through renewable fleets, fuel efficiency, and other measures as the role of SAF grows over time, in addition to offsetting emissions that remain.

Many airlines have made large offset commitments that go beyond CORSIA and offer their customers the option to pay offsetting costs themselves. Overall, however, only about 50 percent of airlines offer customers an opportunity to offset flight emissions, and the process to do so can be cumbersome, with customers redirected to a separate website to opt-in. As our survey showed, very few fliers—less than one percent—make use of voluntary carbon offsetting.

Sustainable aviation fuel

SAF is a solution that can achieve full decarbonization, but it comes with challenges on both the supply and demand fronts. When burned, SAF creates the same amount of CO 2 emissions as conventional jet fuel. The improvement results from the fact that its production process absorbs CO 2 , leading to a reduction in CO 2 emissions of 70 to 100 percent on a life-cycle basis.

In a 1.5°C pathway, our analysis found that SAF would have to account for 20 percent of jet fuel by 2030, or, at a minimum, 10 percent in a scenario in which transportation lags in decarbonization compared with other sectors.

Use of advanced biofuels is a likely near-term solution. The technical feasibility of fuel made from vegetable or waste oils is proven, the product is certified, and some airlines use the fuel in daily operations. But getting the appropriate feedstock and supply chain in place is difficult; building production facilities and refineries is costly. Used cooking oil, a popular ingredient for biofuel, has fragmented availability and is expensive to collect. Other vegetable oils have high costs of production, collection, transportation, and conversion to fuel.

Feedstock resources also involve other environmental risks, such as deforestation and the creation of monocultures. Feedstock sources for biofuels must be selected thoughtfully to limit “food versus fuel” challenges.

Some airlines, including Cathay Pacific Airways and United Airlines, have invested in facilities to demonstrate how municipal household waste could be gasified and subsequently turned into jet fuel. In some regions, the fermentation of wood residues into sustainable kerosene has shown potential as a viable path.

Alternatively, the use of synfuels derived from hydrogen and captured carbon emissions could become a scalable option. Such synfuels require water, renewable electricity to produce hydrogen, and CO 2 . Today, these power-to-liquid fuels are several times the cost of conventional kerosene, though we expect a significant cost reduction for green hydrogen (via reduced costs of renewable electricity and “electrolyzers”) in the coming years. In a first step, CO 2 could be captured as waste gas from carbon-intensive industries, such as steel, chemicals, and cement.

Long term—and to become net-zero CO 2 —the required CO 2 needs to be extracted from the carbon cycle (taken from the air with direct air capture). While this is costly today, the process benefits from cheaper renewable-electricity generation in the future.

While synfuels could become an answer to cutting emissions over the long run, it is unclear, at this point, which SAF sources will emerge as winners. A McKinsey analysis suggests that while current SAF costs are high in relation to kerosene cost, they will come down over time and could reach breakeven between 2030 and 2035, in an optimistic scenario (Exhibit 3).

In effect, SAF presents a classic chicken-and-egg problem. Airlines don’t yet have a viable business case for buying SAF; therefore, its production volume is small, with little economies of scale and insufficient funding (Exhibit 4).

Wanted: More stakeholders for sustainable aviation fuel

Breaking through the which-comes-first problem with SAF would involve a number of groups, each doing its part to put the puzzle together. First, airlines could build and orchestrate a consortium of stakeholders that includes technology providers and oil companies to drive demand and help bridge the cost gap. For example, airlines could commit to buying SAF at a predefined price, or at a price differential to traditional jet fuel, which would eliminate market risks for fuel suppliers.

Ten questions airline executives should be asking

The coronavirus pandemic has created uncertainty for every industry. Airline executives should be asking themselves ten questions about what the crisis means for decarbonization and the possible responses and actions they can take:

• Will the industry and its emissions shrink in the long run because of a fundamental shift in travel behavior?
• Will customers become even more serious about demanding sustainable travel, with growing awareness of climate change?
• What will governments ask in return for state support?
• Could the coronavirus crisis lead to further industry consolidation, resulting in larger average aircraft capacity, improved seat-load factors, and improved fuel efficiency?
• Could the crisis present an opportunity to accelerate fleet replacement or renewal?
• How much upside is left in fuel-efficiency programs to reduce both cost and carbon emissions?
• Could the crisis be an opportunity to harmonize air-traffic control and reduce on-the-ground and in-flight delays?
• What does the demand shock from the coronavirus pandemic mean for CORSIA and “cap and trade” systems, such as the European Union’s Emissions Trading System?
• What will a lasting low kerosene price mean for the economic viability of SAF?
• Could the industry accelerate innovation—for example, into production of SAF?

Second, financial institutions could provide venture capital for building SAF-production facilities and new infrastructure that allows for the anticipated cost savings. Building a coalition of airlines could increase the required volume, resulting in scale effects.

Third, airlines could work with B2B customers willing to pay a premium for the opportunity to decarbonize their employees’ footprints. Microsoft committed to reducing its environmental footprint by promoting SAF and paying for the cost premium. For individual customers, airlines could use loyalty-program rewards as incentives to offset CO 2 through SAF use.

Fourth, policy makers at domestic and regional levels could play a critical role by creating incentives for SAF production and setting appropriate targets. Countries such as Canada and Norway that are willing to apply blending mandates are moving forward on this front. Policy makers could also reallocate aviation taxes back to the industry to fund decarbonization, closing the remaining cost gap between conventional kerosene and SAF.

The coronavirus pandemic has hit aviation hard. Yet as the industry emerges from this painful period, there is an opportunity to move closer to low-carbon goals.

The aviation industry has made great strides in fuel efficiency and operational advancements. But to reach global emission-reduction targets, it will need to move to the next level of decarbonization, and SAF is an option that could get it there. Bolder moves and much deeper collaboration among stakeholders are necessary to build financial structures and programs that can help funnel capital into SAF production.

Because the aviation industry has such long-lived assets, making decisions now is crucial. Finding solutions that bring the industry in line with global emission goals will help ensure that future generations won’t feel the flight shaming of today.

Alex Dichter is a senior partner in McKinsey’s London office; Kimberly Henderson is a partner in the Washington, DC, office; Robin Riedel is a partner in the San Francisco office; and Daniel Riefer is an associate partner in the Munich office.

The authors wish to thank Guenter Fuchs, Nathan Lash, Tapio Melgin, Ole Rolser, Jan Vespermann, and Jop Weterings for their contributions to this article.

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Why is aviation important?

Aviation accounts for a relatively small share of global emissions but is one of the most challenging sectors to decarbonise. Despite reductions in flying during the Covid-19 lockdowns, demand is expected to grow rapidly through 2030. New aircraft can be up to 20% more efficient than the models they replace, but growth in activity has historically outpaced efficiency improvement.

Where do we need to go?

Technology innovation is needed across the sector, including in production of low-emission fuels, improvements in aircraft and engines, and operational optimisation. Demand restraint solutions will also be needed to get on track with the Net Zero Emissions by 2050 Scenario – to curb growth in emissions and ultimately reduce them this decade.

What are the challenges?

Planned production capacity for sustainable aviation fuels will provide just a small fraction of jet fuel demand by 2027. Increasing the use of these fuels to get in line with the Net Zero Scenario will require supportive policies and a significant ramp-up of investments in production capacity.

Why is aviation important? Chevron down

Where do we need to go chevron down, what are the challenges chevron down, tracking aviation.

In 2022 aviation accounted for 2% of global energy-related CO 2 emissions, having grown faster in recent decades than rail, road or shipping. As international travel demand recovers following the Covid-19 pandemic, aviation emissions in 2022 reached almost 800 Mt CO 2 , about 80% of the pre-pandemic level. Many technical measures related to low-emission fuels, improvements in airframes and engines, operational optimisation and demand restraint solutions are needed to curb growth in emissions and ultimately reduce them this decade in order to get on track with the Net Zero Emissions by 2050 (NZE) Scenario. 

Country and regional highlights Chevron down

Political agreement on targeting net zero for aviation has been complemented by fiscal and regulatory policies to promote sustainable aviation fuels in major markets

Notable progress towards getting aviation on track includes the following: 

• The 184 member states of the International Civil Aviation Organization (ICAO) adopted in 2022 a long-term global aspirational goal (LTAG) of net zero carbon emissions from international aviation by 2050. 
• In 2022 the United States announced important tax credits and a competitive grant programme under the Inflation Reduction Act , which will allocate USD 3.3 billion to scaling up sustainable aviation fuel (SAF) production, with the aim of meeting its 3 billion gallons milestone by 2030 . 
• In the European Union, the European Parliament and Council reached a political agreement in 2023 on the rules of ReFuelEU Aviation on the schedule of minimum SAF blend-in shares, with sub-targets for synthetic fuels, through 2050. 
• In 2022, following its announced Jet Zero pledge, the United Kingdom dedicated GBP 165 million to support SAF projects, with a plan to have at least 5 commercial SAF plants under construction by 2025. 

CO2 emissions Chevron down

CO2 emissions from aviation have reached 80% of their pre-pandemic peak

CO2 emissions in aviation in the Net Zero Scenario, 2000-2030

Aviation emissions rose in 2022 to reach nearly 80% of their pre-pandemic peak in 2019. After increasing at an average of 2.3% per year from 1990 to 2019, direct CO 2 emissions from fossil fuel combustion plummeted from more than 1 000 Mt CO 2 in 2019 to less than 600 Mt CO 2 in 2020 in the context of the Covid-19 pandemic. As demand from air passengers recovered in 2022, emissions increased in all regions with the exception of China (due to the zero-Covid policy) and Russia (due to the invasion of Ukraine), reaching almost 800 Mt CO 2 . CO 2 emissions are expected to grow rapidly and to surpass their 2019 level around 2025.  

Multiple measures are required to promote the technologies, sustainable aviation fuels (SAF) and demand-side management needed to bring the currently rising emissions level below 1 000 Mt CO 2 by 2030, in line with the NZE Scenario. Policy and fiscal support should prioritise improvements in energy efficiency, stimulating investment in pre-commercial and low-emissions SAF, and developing alternatives to jet kerosene, such as electricity- or hydrogen-powered aircraft.

Energy Chevron down

Improvements in energy intensity have not been sufficient to counterbalance energy demand growth in recent years

Energy intensity of commercial passenger aviation in the Net Zero Scenario, 2000-2030

From 2010 to 2019, average fuel efficiency per revenue tonne kilometre (RTK) equivalent travelled improved by 1.8% per year thanks to the introduction of more efficient aircraft and engines , with improvements over the decade nearly reaching ICAO’s aspirational goal of 2% per annum through 2050. However, efficiency improvements have not kept up with demand growth, which grew at an average rate of over 5% annually between 2010 and 2019. To stay on track with the Net Zero Scenario, efficiency will need to improve at a rate of 2% per year through 2030, on a par with the historical average improvements over the past two decades.  

In addition to technical efficiency improvements in engine and airframe designs, improvements in payload and traffic efficiency (i.e. the weight of cargo and number of passengers carried per aircraft) have also contributed to reducing the energy intensity of aircraft operation. Payload efficiency deteriorated between 2020 and 2022, as planes were flown with fewer passengers despite some compensatory increase in freight payloads in the bellies of passenger aircraft. 

Activity Chevron down

International passenger activity more than doubled in 2022 compared to the previous year, closing the gap with pre-Covid levels

Global total commercial air passenger traffic, 2019-2022

Total commercial (international plus domestic) air passenger activity increased by around 70% in 2022, and now stands at three-quarters of pre-pandemic levels. Increasing activity in international aviation was the main driver, with more than 150% growth , after a year of slower recovery compared to domestic aviation. The reopening of international travel in China provides an outlook for even higher growth from the beginning of 2023, as passenger and cargo activity return to pre-pandemic levels. 

Air cargo contracted by 8% in 2022 after a historical peak in 2021, as a result of high inflation, disruption of trade flows due to the war in Ukraine, and the strong US dollar making commodities traded in US currency more expensive. 

Technology deployment Chevron down

Sustainable aviation fuels are critical to decarbonising aviation

Currently, demand for aviation fuel is dominated by jet kerosene, while SAF account for less than 0.1% of all aviation fuels consumed. Manufacturers and operators are increasingly testing flights that are entirely fuelled by SAF, which can be deployed in current infrastructure, engines and aircraft with minor adjustments to fuel delivery equipment. However, planned production capacities will provide just 1-2% of jet fuel demand by 2027. Increasing SAF use in aviation to 10% by 2030 in line with the Net Zero Scenario will require a significant ramp-up of investment in capacity to produce SAF and supportive policies such as fuel taxes and low-carbon fuels standards. 

Commercial adoption of SAF will be driven by policies such as the aforementioned incentives for SAF production in the United States and the United Kingdom , and the European Union’s proposed ReFuelEU regulation. The current ReFuelEU Aviation proposal excludes crop-based SAF due to sustainability concerns, and the potential to scale up biojet kerosene supply based on animal fat and waste oil feedstocks (which are included in the proposed regulation) is limited by their supply. Supporting research and development on advanced biofuel technologies can unlock more abundant and cheaper feedstocks such as agricultural residues, dedicated energy crops and municipal solid waste. In the longer term, synthetic fuels based on hydrogen produced using electrolysers (and running on low-emissions or renewable electricity), combined with CO 2 from biogenic, concentrated waste streams or atmospheric sources can provide an alternative, although commercialisation may be challenging. 

Revolutionary designs are needed to achieve efficiency improvements of more than 2% annually in the longer term

Incremental improvements to engines, materials, aerodynamics and mild hybridisation can and should be implemented. However, “revolutionary” designs , such as new airframe configurations to enable further efficiency improvement, and alternative propulsion technologies including electric or hydrogen-powered aircraft, may also play a role.

Innovation Chevron down

Tests and prototypes showcase innovations in hydrogen-powered aircraft

Hydrogen can be used via direct combustion in jet engines, or in fuel cells to generate electricity for electric motors, or a combination of the two. However, using hydrogen in aircraft poses significant challenges, including the need for innovative fuel storage and delivery methods, low-cost and lightweight cryogenic tanks, and redesigned airframes to accommodate them. By 2040 hydrogen aircraft are likely to have a maximum range of under 3 500 km , serving at a maximum about half of all fuel consumption in current commercial aviation operations. 

Test flights for aircraft equipped with fuel cell-powered electric motors have taken place in early 2023, with ZeroAvia flying a 19-seat aircraft equipped with a hydrogen-electric engine on its left wing, and Universal Hydrogen flying a 40-seat regional aircraft at high altitude, with one of its engines powered by fuel cell. This followed its demonstration of prototype modular capsules that can store liquid hydrogen for up to 100 hours and can be transported by semi-truck. 

Demonstrations of alternative propulsion systems have also progressed from late 2022 onwards. Airbus 's ZEROe programme produced a prototype of a cryogenic hydrogen tank that allows hydrogen to be carried in its liquid form at extremely low temperatures. Rolls-Royce and easyJet tested combusting hydrogen to run a regional jet engine with hydrogen produced from wind and tidal power. Avio Aero has launched a demonstration programme for megawatt-level hybrid electric propulsion technologies, coupling a propulsion engine with a fuel cell-powered electric motor. H2FLY has begun the integration of a liquid hydrogen storage system tank in its four-seat aircraft with hydrogen-electric propulsion. 

Battery electric propulsion is currently limited to very small aircraft and short range

Battery electric aircraft have no direct emissions, potentially much lower operational and maintenance costs (dependent on battery durability), high efficiency and create far lower noise pollution. However, current battery energy density and weight severely restrict the range of battery electric flights and the size of the aircraft. In September 2022 Eviation performed a test flight of its 9-seat electric aircraft, with maximum flight range of around 450 km. 

The success of deploying electric aircraft technologies will largely depend on the evolution of battery technologies. The energy density of today’s Li-ion batteries is around 200 Wh/kg (with a current practical limit of 300-400 Wh/kg) at the pack level, but for short-haul flights over 1 000 km, a battery pack energy density of at least 800 Wh/kg would be needed. 

World’s first airport liquid hydrogen refuelling facility under construction

Airbus and ArianeGroup are working towards building the first liquid hydrogen refuelling facility for ZEROe aircraft at Blagnac airport in Toulouse, France. 

Policy Chevron down

Governments are increasing fiscal support for SAF production and mandating SAF use

Production of SAF gained substantial support through the passage in 2022 of the Inflation Reduction Act (IRA) in the United States, with USD 3.3 billion in tax credits and a competitive grant programme allocated to SAF. The IRA provides USD 1.25 per gallon (USD 0.33 per litre) of SAF produced, provided that the lifecycle emissions are no more than 50% of those of fossil jet kerosene. A supplemental 1 cent credit is available for each percent that the lifecycle emissions reduction exceeds 50%. 

In addition to amending the European Union Emissions Trading System to phase out allowances given to the aviation industry by 2026, in Q1 2023 the European Council and Parliament agreed on rules mandating a minimum share of SAF with sub-targets for synthetic fuels. Individual countries such as France and Norway already have SAF blending mandates in place, while Sweden’s GHG emissions intensity reduction target will also drive SAF adoption. In 2023 the Swedish government also announced its aim to invest SEK 15 million (Swedish kronor) annually to support research and development of electric aircraft. The United Kingdom, following its 2022 Jet Zero pledge, has dedicated GBP 165 million to support SAF projects, with funding allocation running to 2025. 

In the Asia Pacific region, in 2022 Japan proposed legislation mandating that SAF must account for 10% of aviation fuel by 2030. In the same period the Civil Aviation Administration of China also set ambitions to increase SAF use and lower GHG emissions intensity. 

View all aviation policies

• Policies and Measures database (PAMS) circle-arrow

International collaboration Chevron down

International aviation has pledged to reach net zero emissions by 2050

In late 2022, ICAO member states adopted a long-term global aspirational goal (LTAG) to achieve net zero carbon emissions from international aviation by 2050. The agreement aims to reduce emissions within the sector itself (i.e. directly from aviation activity, as opposed to via offsetting emissions through purchase of credits). Although it remains non-binding and lacks intermediate goals, member state governments are expected to produce action plans within their own national timeframe and capabilities. 

Additionally, countries agreed on a new baseline for the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) at 85% of the 2019 emissions level of international aviation. Emissions beyond this would need to be reduced by using sustainable aviation fuels or by purchasing certified emissions reductions to offset CO 2 emissions. ICAO approved addition programmes for CORSIA compliance during the pilot phase, many of which rely on offsets outside the energy sector. 

Private sector strategies Chevron down

Airlines are moving towards offtake agreements with fuel suppliers to supply SAF

Increasing announcements of SAF offtake agreements between fuel suppliers and airlines marked a stark increase in contracted volume from 9 billion litres in 2021 to 22 billion litres in 2022. The largest offtake volume per year purchase to date was agreed between Gevo and OneWorld Alliance , to be sourced from ethanol from inedible corn products. Many of the contracted volumes have planned delivery after 2025, as new SAF plants take around three years to build after a final investment decision has been taken. 

Acknowledgements Chevron down

We would like to thank the following external reviewers:

• Lynnette Dray, University College London
• Haldane Dodd, Air Transport Action Group

Recommendations

Supply-side and demand-side policies will need to mutually reinforce each other to scale up SAF production and demand

Tax aviation fuels according to impact, acknowledging that only a minority of the world flies, the aviation sector can lead on bringing nascent decarbonisation options to scale.

Last update on 11 July 2023

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Renewables 2022

Biojet fuel demand expands to 3 900 MLPY in our main-case forecast – 37 times the 2021 level – to account for nearly 1% of total jet fuel consumption.

Fuel report — December 2022

Authors and contributors

Lead authors Hyeji Kim Jacob Teter

Policies to support SAF consumption and boost growth are needed to make SAF more widely available and economically viable.  

On the demand side, blending mandates provide clear long-term demand signals beyond offtake agreements. Low-carbon fuel standards provide less clarity on required volumes, but this is balanced by providing a clear regulatory framework to reduce the lifecycle emissions of SAF. By combining blending mandates with GHG emissions and sustainability criteria, regulatory frameworks such as the proposed ReFuelEU Aviation aim to achieve market certainty at the same time as incentivising uptake of less mature and higher cost SAF production pathways in the mid- to long term.  

Funding and financial de-risking will be needed to promote continued innovation around sustainable production processes including novel feedstocks (wastes, residues, marginal land, double cropping) and support the leap from demonstration to commercial plants. This will also be needed to drive investment at all stages of research, and to enable power-to-liquids jet kerosene to scale up rapidly. 

Both supply and demand of SAF are highly concentrated in advanced economies today. Meeting the growing demand for air travel in emerging and developing economies will require technical assistance and capacity building to accelerate the availability and use of SAF. Such support can help emerging market and developing economies to leverage domestic natural resource endowments such as biomass, solar and wind, and thereby scale up high value-add industries in the clean energy economy.

Taxing GHG emissions beyond the CORSIA scheme is critical to more equitably reflect the climate impacts of air travel. As the additional costs of these taxes are passed on to passengers, they can help curb demand growth, while revenues generated could be used to foster low-emission innovation in SAF production or engine and airframe design.  

Since frequent fliers likely account for the majority of commercial aviation emissions , progressive tax rates that increase with flight frequency as well as higher taxes on premium class tickets could discourage excessive flying, especially as jet kerosene is currently taxed at lower levels than residential electricity or automative fuels in many regions. However, changing tax structure is complicated by taxation conditions on international flights agreed in the Chicago Convention of 1944 . 

Certain airlines propose offset options to consumers, such as paying extra towards SAF . Some have set corporate targets to supply increasing shares of fuels with SAF , and are actively seeking offtake agreements that secure demand for nascent SAF markets. 

Actions from leading airlines and airports that serve as key international and domestic hubs can generate the market pull that is needed to catalyse adoption of efficient operations, best-in-class technologies and SAF. Those that act early will benefit not only from asserting their leadership in corporate social responsibility, but from being the first to gain experience of innovative practices and technologies that will eventually need to be adopted more widely. Investors, lenders and consumers will be instrumental in driving uptake of SAF by funding airlines and setting corporate travel and freight transport policies. 

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Reducing air travel by small amounts each year could level off the climate impact

Postdoctoral Researcher in Weather and Climate Modelling, University of Oxford

Disclosure statement

Milan Klöwer receives funding from the UK's Natural Environmental Research Council, the Copernicus Programme of the European Commission and the European Research Council.

University of Oxford provides funding as a member of The Conversation UK.

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Just before the pandemic, aircraft engines were burning one billion litres of fuel a day. But then the number of daily civil aviation flights fell from 110,000 to less than 50,000 during 2020, on average. With the easing of travel restrictions, air traffic is increasing back towards its pre-pandemic peak.

Most world leaders and delegates will have flown to Glasgow to attend COP26 – the 26th annual UN climate change summit – in person. But as they haggle over emissions targets to limit global warming to 1.5°C, and not 3°C or more , aviation is unlikely to be included in them, given the lack of low-carbon alternatives to long-haul flights.

But it should be. In new research , my colleagues and I calculated that if the aviation sector continues to grow on its present trajectory, its jet fuel consumption will have added 0.1˚C to global warming by 2050 – half of it to date, the other half in the next three decades.

Aviation is responsible for 4% of the 1.2°C rise in the global mean temperature we have already experienced since the industrial revolution. Without action to reduce flights, the sector will account for 17% of the remaining 0.3°C left in the 1.5°C temperature target, and 6% of the 0.8°C left to stay within 2°C. Airlines effectively add more to global warming than most countries.

Warming footprints

At the current rate, the world will have warmed by 2°C within three decades . To quantify how different activities contribute to warming, scientists measure carbon emissions. This is because how much the Earth warms is proportional to cumulative carbon emissions in the atmosphere. This is a very good approximation in many cases, but it is inaccurate for emissions caused by aeroplanes travelling at altitudes of up to 12 kilometres.

As well as CO₂, aircraft engines emit nitrogen oxides, water vapour, sulphur and soot, causing contrail cirrus clouds and other complicated chemical reactions in the atmosphere. The sum of these so-called non-CO₂ effects adds more warming on top of the CO₂ emissions. So the total warming footprint of aviation is between two and three times higher than a conventional carbon footprint.

While a large share of a flight’s CO₂ emissions remain in the atmosphere for many thousands of years, the non-CO₂ effects diminish over time, vanishing within about ten years . So any growth in aviation, measured in global jet fuel consumption, has an amplified impact as both CO₂ and non-CO₂ effects add up.

But a decline in aviation can partly reverse some warming, as the non-CO₂ effects disappear over time until only the CO₂ effects remain. Think of the non-CO₂ effects like a bathtub – it fills up when the taps are turned further and further, despite a slow outflow down the plughole. But the same bathtub will eventually empty if the taps are gradually turned down.

The non-CO₂ effects of flights on the atmosphere will slowly disappear if fewer and fewer flights are taken, so that aviation’s contribution to warming eventually levels off. In that situation, the increase from continued CO₂ emissions would balance the fall in non-CO₂ effects, and although aviation would still contribute to climate change, the total warming from both would remain constant over time. How much would aviation need to shrink to level off its influence on global warming?

Our calculations show that flying does not need to stop immediately to prevent aviation’s contribution to global warming expanding. Flying has already caused 0.04°C of warming to date. But with a yearly decrease of 2.5% in jet fuel consumption, currently only achievable with cuts in air traffic, this warming will level off at a constant level over the coming decades.

When do we really need to fly?

COVID-19 had a huge impact on the aviation sector. Air traffic is still approximately 10-20% below pre-pandemic levels, but is rebounding quickly . Politicians should shift subsidies from flying to more sustainable modes of transport, such as train journeys. And there is much more that can be done.

Lockdowns and the shift to remote working made many people rethink the necessity of flying. People resolving to fly less can contribute considerably to reducing the number of unnecessary flights. Combining in-person and virtual attendance in hybrid meetings wherever possible is a great way to support that shift.

Reducing the space that business classes take on aeroplanes is another way to cut the number of flights, as it allows more passengers to travel on one flight.

Not allowing airport expansions could also have a big impact. The UK’s Climate Change Committee, an expert body which advises the UK government, has recommended not expanding airports to align the sector with climate targets. Yet the expansion of Heathrow airport is currently planned to go ahead .

Sustainable aviation fuels, and hydrogen or electric planes, are being developed, but none of these technologies are currently available at the necessary scale. At the moment, there is little chance of the aviation industry meeting any climate targets if it aims for a return to its pre-pandemic rate of growth.

This story is part of The Conversation’s coverage on COP26, the Glasgow climate conference, by experts from around the world. Amid a rising tide of climate news and stories, The Conversation is here to clear the air and make sure you get information you can trust. More.

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4 ways airlines are planning to become carbon neutral

The airline industry believes its quickest path to net-zero is replacing jet fuel with sustainable aviation fuel. Image:  Unsplash/Pascal Meier

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Stay up to date:, climate change.

• The airline industry is responsible for nearly 3% of global carbon dioxide emissions.
• It has pledged to be carbon neutral by 2050 by focusing on four key strategies.
• These include greener fuel, carbon offsets and utilizing the power of hydrogen.

Launching a 300-ton plane full of people into the sky and propelling it at 500 miles (805 km) an hour requires a lot of energy. So, taking off without adding greenhouse gases to the atmosphere will take some doing.

The airline industry, responsible for nearly 3% of global carbon dioxide emissions, has pledged to hit net zero by 2050 to help curb global warming.

But with travel demand likely to add to the 100,000 or so flights daily, some worry they could struggle with that goal .

Airlines say they are optimistic . Here are some of the strategies they are looking at:

The airline industry believes its quickest path to net-zero is replacing jet fuel with “sustainable aviation fuel” (SAF) made from renewable sources, such as plants or used cooking oil.

In theory, SAF can cut flight emissions by around 80%, depending on how it is made.

But SAF is not widely available because of cost. The United States and other countries are considering subsidies to bring prices down and supplies up. In the meantime, some airlines are blending small amounts into their fuel.

There are other concerns, including whether planes can run properly on pure SAF, as opposed to a mix. Engines designed for petroleum-based fuel rely on its oily qualities to lubricate internal parts and protect gaskets and seals. It is unclear if SAF offers that effect on its own.

Boeing (BA.N) is studying the issue and has committed to ensuring its planes are certified for 100% SAF by 2030.

Even if SAF can replace petroleum fuel completely, it still only reduces emissions by 80% at best.

The rest could be written off with carbon offsets – financial instruments that allow an emitter to pay someone else to cut emissions.

Offset credits are generated by investing in clean energy projects, planting trees, or supporting other types of efforts that keep emissions from the atmosphere. Airlines and other industries are already making these investments.

But scientific uncertainty as well as a lack of transparency and international quality standards mean it is impossible to be sure those using offsets are cutting the promised emissions.

Negotiators at the U.N. climate summit in Glasgow are trying to solve the issue by agreeing on standards for government-run carbon markets, which would likely then inform rules for voluntary ones. But delegates are not sure a deal can be struck.

Direct eye capture

United Airlines (UAL.O) has shunned carbon offsets, which its CEO Scott Kirby calls the "the height of greenwashing".

Instead, UA is betting on direct air capture (DAC), a technology still in development that would suck carbon dioxide directly out of the atmosphere and store it underground.

The U.S. airline is a "small minority" partner in 1PointFive Inc's project in Texas, which hopes to become the world's first commercial direct air capture facility with a capacity to remove 1 million tons of CO2 from the air annually.

As other sectors proceed to decarbonize, the aviation sector could account for a much higher share of global greenhouse gas emissions by mid-century than its 2%-3% share today.

Sustainable aviation fuels (SAF) can reduce the life-cycle carbon footprint of aviation fuel by up to 80%, but they currently make up less than 0.1% of total aviation fuel consumption. Enabling a shift from fossil fuels to SAFs will require a significant increase in production, which is a costly investment.

The Forum’s Clean Skies for Tomorrow (CST) Coalition is a global initiative driving the transition to sustainable aviation fuels as part of the aviation industry’s ambitious efforts to achieve carbon-neutral flying.

The coalition brings together government leaders, climate experts and CEOs from aviation, energy, finance and other sectors who agree on the urgent need to help the aviation industry reach net-zero carbon emissions by 2050.

The coalition aims to advance the commercial scale of viable production of sustainable low-carbon aviation fuels (bio and synthetic) for broad adoption in the industry by 2030. Initiatives include a mechanism for aggregating demand for carbon-neutral flying, a co-investment vehicle and geographically specific value-chain industry blueprints.

Learn more about the Clean Skies for Tomorrow Coalition's impact and contact us to find out how you can get involved.

The technology has yet to be proven up to scale. And it's expensive, costing hundreds of dollars to capture just one ton of CO2. Several previous carbon capture and storage (CCS) efforts have failed .

Kirby said he thinks the 1PointFive project will work, but isn't sure if it will be a cost-effective option.

Electric and hydrogen

Other options being studied include whether battery capacity can be scaled up to power planes, and whether hydrogen fuel made with renewable power can be produced in the quantities needed.

The technologies are still far from commercial use, with batteries heavy and hydrogen fuel still unproven in planes.

Have you read?

Japan airlines ditches 'ladies and gentlemen' for gender-neutral greetings, united airlines plans to use jet fuel made from trash, these 4 charts show the crisis faced by airlines – and the possible way ahead.

Rolls-Royce held a 15-minute test flight of a small electric plane in September, calling it a "milestone on the aviation industry’s journey towards decarbonization".

The engine-maker said it expects a market for electric "flying taxis" for short distances within a few years, while longer flights would probably need other technologies.

As for hydrogen, Airbus (AIR.PA) says it will develop the world's first commercial aircraft fueled by the gas by 2035.

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• Published: 07 March 2022

Different approaches to reducing aviation emissions: reviewing the structure-agency debate in climate policy

• Nives Dolšak 1 &
• Aseem Prakash   ORCID: orcid.org/0000-0002-7364-0135 2  

Climate Action volume  1 , Article number:  2 ( 2022 ) Cite this article

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• Climate-change policy

Aviation emissions account for about 2.5% of global carbon emissions, and by 2050, their share could rise to 22%. This review article explores how climate scholars view the role of structural (policy- or business-focused) or agentic (individual-focused) approaches in reducing these emissions. From a structuralist perspective, aviation emissions require policy changes because they reflect regulatory and business failures to address the climate crisis. By itself, individual actions will not significantly reduce emissions. Moreover, focusing on personal (agentic) action might allow governments and firms to disavow their role in the climate crisis. From an agentic perspective, aviation emissions reflect carbon-intensive lifestyles. Even within the existing policy structures, individuals can reduce the carbon footprint of their travel. At the same time, individuals can serve as influencers, voters, and social movement participants to pressure governments and businesses to develop low-emission air travel policies. Rather than viewing agency and structures as distinctly separate approaches, we suggest that they could co-evolve to create pathways to reduce aviation emissions. Policy initiatives can facilitate individual efforts to reduce air travel emissions, and individual action could shape policies structuring their choices.

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Introduction

Aviation emissions account for about 2.5% of global emissions but drive about 7.2% of global warming due to high-altitude atmospheric effects (Lee et al., 2018 ). If it were a country, the aviation industry would be the world’s 7th largest carbon emitter. Its emissions are more than twice that of California, which accounts for 1.2% of global emissions (EPA 2019 ). But for the interruption in air travel in 2020–2021 due to COVID-19, aviation emissions have been growing rapidly. By 2050, their share could rise to 22% of global emissions (EU, 2015 ).

Aviation emissions have an equity component as well. Because climate change costs are distributed asymmetrically across countries, communities, and generations, equity issues are at the forefront of climate debates (Schlosberg & Collins, 2014 ; Shue, 2014 ; Caney, 2014 ; Dolšak and Prakash, 2022 ). Aviation emissions epitomize climate inequity: 1% of the world’s population is responsible for 50% of carbon aviation emissions (Gössling and Humpe, 2020 ; Nicholas, 2021 ). While individual wealth makes most air travelers immune from the worst consequences of climate change, underprivileged individuals suffer disproportionately from increased frequency and severity of extreme weather events, droughts, new disease vectors, and human displacement (Füssel, 2010 ; Green, 2016 ).

The study of the aviation sector provides insights into where climate mitigation actions have been targeted. Scholars favoring structural solutions tend to discount the role of individual action in climate mitigation. Others note the importance of individual agency, which manifests in terms of consumer choices and political action, eventually helping to change the policy framework that structures individual action. In this review essay, we examined two categories of approaches that scholars have proposed to reduce aviation emissions: agentic and structural. We employ a scoping approach (Davis et al., 2015 ) to survey the literature on approaches to reducing aviation emissions. We employed a two-stage process. In the first stage, we examined climate and environmental policy journals (since 2010) to identify appropriate articles based on a careful reading of the abstracts. After reading the identified articles, we examined their bibliographies to understand where else articles on aviation emissions have been published. We then examined these journals as well. Second, to ensure that we did not miss out on articles published in the journals we had not surveyed, we searched for publications on Google Scholar, using keywords such as “aviation emissions,” “airline emissions,” “flying shame,” “carbon offsets,” “climate action,” “climate mitigation,” “climate movements,” “green purchasing,” “and “agency-structure.” On Google Scholar, we also examined the literature on “social marketing” because climate-inspired consumer choices could be subsumed in the category of pro-social consumer behaviors. Our objective was not to assess whether the agentic or structural perspectives are more dominant in the research or more effective in emission reductions. Instead, our objective was to examine key approaches scholars outline, the strengths and weaknesses of agentic and structural approaches, and how this debate about modes and drivers of climate action speaks to the broader social science inquiry about the role of structure and agency in addressing climate mitigation

The agentic perspective assumes that individuals enjoy some discretion in deciding whether to satisfy their transportation needs via air travel. While individuals might be motivated to take pro-climate actions, they may not have information about aviation’s carbon footprint or low-emission alternatives. If so, information provision could help individuals make superior climate choices. However, scholars note that agentic solutions fail when individuals ignore their climate footprints. But more worrisome, some critics suggest that by taking responsibility for the climate impact of their lifestyles, individuals allow governments and firms to disavow their role in the climate crisis and blame it on individual choices (Mann, 2021 ). Thus, well-intentioned consumer action provides the cover for regulatory and business failure.

In contrast to the agentic perspective, structuralists suggest that carbon-intensive lifestyles, of which air travel is a prime example, are outcomes of public policies such as fuel subsidies. Moreover, given the scale of the climate crisis and the need for quick action, policy changes are required. Individual choices are also shaped by business-financed advertising (a structural factor) that glorifies social practices, such as travel to exotic destinations, with substantial carbon footprints (Peeters and Dubois, 2010 ; Lenzen et al., 2018 ). Because individuals seldom exercise real choices, government and business policy changes are necessary to tackle individual-level, consumption-related emissions.

Structural approaches, particularly the ones focused on governmental policy, can bring about large-scale changes but face political hurdles. Agentic approaches, in contrast, may not work at the same scale but also face fewer political hurdles, given their micro focus. Yet, the agent-structure dichotomy might become less sharp in the long run. The reason is that the popularity of individual agentic action could motivate structural changes because political and business leaders cannot afford to be oblivious to public pressure. For example, the popularity of ESG (environmental, social, and corporate governance) investing (as opposed to shareholder wealth maximization) among major financial institutions might reflect a structural change in the financial sector in response to pressure from climate movements (Kotsantonis et al., 2016 ). Thus, instead of viewing them as substitutes, climate scholars should explore conditions under which agentic and structural approaches could co-evolve and complement each other.

In the next section, we explore the structure-agency debate in the context of low-carbon consumption and identify impediments to pro-climate choices and how these might be overcome. In the “ Aviation emissions: structural and agentic approaches ” section, we examine airline emissions from both the structural and agentic perspectives. In the concluding section, we draw lessons for climate action and outline themes for future research.

Climate mitigation: structural and agentic approaches

Because climate change reflects the overuse of global commons, the climate discourse tends to focus on regulatory and business failures (a structural issue) as opposed to an absence of agentic “climate citizenship” (Wolf et al., 2009 ; Vihersalo, 2017 ). The landmark case of Juliana v. United States illustrates this argument. In this case, young plaintiffs contended that the US government had failed in its obligation to combat climate change. The plaintiffs argued that the atmosphere is a resource like air and water that the government is expected to hold in public trust. Consequently, the federal government has violated younger generations’ constitutional rights to life and liberty by not regulating its use. Importantly, the plaintiffs did not hold individual choices or consumption patterns accountable for the climate crisis: for them, the problem was structural, and therefore, blame was solely on the government.

But why have governments failed to regulate? Climate policies targeting fossil fuels impose an economic burden on specific sectors while everybody enjoys their benefits. In the absence of compensation for the sectors bearing mitigation costs (on the subject of “just transition,” see Newell and Mulvaney ( 2013 )), these sectors and their allies have mobilized against mitigation policies. Moreover, governments have subsidized it instead of taxing the fossil fuel industry for the externalities it imposes on societies (Pigou, 1924 ). Thus, government failure is rooted in acts of omission (inadequate regulations) and commission (granting fossil fuel subsidies).

Regulating carbon emissions faces another challenge: the “China Excuse” (Dolšak and Prakash 2015 ). Because China is a non-Annex 1 country under the United Nations Framework Convention on Climate Change, it is not subject to mandatory emission reductions. Yet, the Chinese emissions are expanding, and since 2005, China has become the top carbon emitter. Ignoring the issue of historical responsibility, anti-climate actors see climate regulations as putting the US fossil fuel industry out of business, although China continues to build coal plants. As we discuss subsequently, the challenges in enacting new climate regulations probably underscore the need for consumer climate action which can take place independent of government policy.

Structures can be provided by businesses as well, especially when businesses voluntarily correct regulatory inaction (Matten and Moon, 2008 )? Corporate social responsibility is on the agenda for modern corporations. Until recently, most companies did not embrace corporate climate responsibility, and some even funded the climate denial movement (Brulle, 2014 ). In recent years, however, many firms have adopted climate policies beyond their regulatory requirements. They have switched over to renewable energy, putting pressure on state governments to support renewable portfolio standards (Outka, 2019 ). A growing number of firms have also pledged to net-zero emissions by 2050. Yet, it is not clear if these commitments pertain to Scope 1 and 2 emissions (that result directly from the company’s activities or from electricity or heat that the company purchases from elsewhere) or if they also take into account Scope 3 emissions that pertain to their supply chain and consumers. The issue of the role of consumer choice, the agentic dimension to mitigation, is critical in addressing Scope 3 emissions.

Why do individuals not adopt low-emission lifestyles? Some consumers might have pro-climate preferences, but they might not recognize how their actions contribute to the climate crisis (Ropke, 2009 ). For Smith ( 1983 ), these consumers are “culpably ignorant” because they ought to connect the dots between consumption and emissions. Some consumers might recognize this link and yet believe that their actions alone cannot make a difference at the global level, the “causal inefficacy” hypothesis (Jamieson, 1992 ). Others might want to purchase low-carbon products but lack the tools to assess the carbon footprints of different products. “Carbon calculators” can help in this regard (Salo et al., 2019 ), but their proliferation might confuse when calculators generate different results for the same activity (Padgett, 2008 ).

Information can motivate behavioral changes when it is contextualized (Nerlich et al., 2010 ). A carbon calculator might reveal that the economy-class flight from London to New York creates almost 1 ton of CO 2 emissions. This number might not mean much per se. However, if the passenger is also told that this is greater than the annual per capita emissions in 56 countries, this information might motivate pro-climate action, such as not flying at all or at least purchasing carbon offsets. Alongside carbon calculators, climate labels, such as Amazon’s Climate Pledge label, can provide climate information about specific products (Prakash and Potoski, 2006 ). Yet, consumers might be skeptical of climate labels due to greenwashing concerns (Wright and Nyberg, 2017 ). Thus, even motivated consumers wanting to adopt low-carbon lifestyles face considerable informational and cognitive hurdles.

Inter-connected consumption routines also impede pro-climate purchasing (Devinney et al., 2006 ). As “theories of practice” suggest, consumers may not evaluate the climate impact of individual actions in a piecemeal fashion (Salo et al., 2019 ). The reason is that individuals might be “locked-in” due to inter-connection among household activities. For example, an individual might want to stop using a car for office travel and switch to public transportation (Laakso, 2017 ). But this individual might also use a car to shop for groceries and to pick up children from their daycare. A switch to public transportation might reduce the carbon footprint of office commute but could jeopardize the person’s ability to perform household chores. Thus, climate policies might not lead to behavioral changes such as discontinuing driving unless policies can create system-level changes where this individual can rely on public transportation to travel to the office, do groceries, and pick up their children from daycare.

While government and business policies certainly affect how individuals exercise their consumption choices, could consumers influence structures that influence their choices? Fragnière ( 2016 ) suggests that consumers can do so collectively. Social movements have employed boycotts (and sometimes buycotts as well) to target firms and governments. Beck ( 2019 ) notes the cases of Irish peasants boycotting an English land agent, Charles Cunningham Boycott. Rev. Martin Luther King, Jr. organized the Montgomery bus boycott during the Civil Rights movement.

Under what conditions do boycotts influence the practices of the boycotted (Stolle and Micheletti, 2013 )? For example, would businesses change practices only when the social movement pressure hurts their competitive position, profits, and stock prices (Pacheco and Dean, 2015 )? Or would businesses react because they fear new regulations or the loss of legitimacy with stakeholders (Friedman, 1999 )? As we discuss below, the “flight shame” movement is an example of consumer shaming targeted both at consumers (the direct target) and at the industry itself (the indirect target). By stigmatizing the act of flying (Cohen et al., 2011 ), it is shaping consumer demand and corporate behaviors and eventually contributing to new regulatory policies. Thus, social movement pressure might create pro-climate social norms that shape consumption choices and motivate regulatory and business initiatives to reduce aviation emissions.

In sum, both agentic and structural approaches to climate mitigation face considerable challenges. In the next section, we apply insights from the broader study of climate action to the specific case of aviation emissions.

Aviation emissions: structural and agentic approaches

Structural approaches to air travel emissions.

Structural reasons contribute to the popularity of air travel. Scholars note that air travel is driven by income (“income effect”) and price (“substitution effect”) because demand for air travel has high income and price elasticities (Beckens and Carmignani, 2020 ). The substitution effect means that because airlines have dropped prices in the last two decades, individuals substitute air travel for other transportation modes, especially railways, which have a smaller carbon footprint.

But why have airlines dropped prices? Policy and institutional factors come into play here. Privatization and deregulation have led to the emergence of low-cost airlines (Clewlow et al. 2014 ), making air travel accessible to a larger number of people. This also means that along with a substitution effect, price declines increase real incomes and create an income effect as well.

Low ticket prices also result from government subsidies, especially on fuel. Since the 1944 Chicago Convention, which gave birth to the International Civil Aviation Organization (ICAO), governments are effectively prohibited from placing a value-added tax on international travel tickets (Havel and Sanchez, 2011 ). Yet, national, regional, and global policy changes are in motion — probably aided by social movement pressure on the airline industry. In 2012, the European Union (EU) began including emissions from intra-EU travel in the EU-Emission Trading Scheme (Scheelhaase et al., 2018 ). In recent years, Germany and France have enacted an aviation tax. France is proposing to ban flights where trains could cover the distance in less than 2.5 h. Although the ICAO has opposed new international rules to govern aviation emissions (Petersen, 2008 ), it has initiated measures to reduce the industry’s climate impact. In 2016, it rolled out CORSIA, the Carbon Offsetting and Reduction Scheme for International Aviation, to limit aviation’s “net emissions” to their average 2019–2020 levels. Due to the decline in air travel in response to COVID-19, there is a proposal to use only the 2019 emissions as the baseline.

While CORSIA is an industry-level response, airlines individually are also taking pro-climate steps. At one extreme, some airlines are taking the drastic step of “demarketing” (Kotler, 2011 ) by asking consumers to reduce flying. KLM’s “Fly Responsibly” campaign urges customers to consider alternative means of transportation, such as trains, for their short-haul travel needs (Hesse and Rünz, 2020 ). Others are taking less drastic measures, such as inducting modern low-emission aircraft. But most focus on carbon offsets. Alaska Airlines, Air Canada, Japan Airlines, and Cathay Pacific provide carbon calculators on their websites along with the opportunity for travelers to purchase carbon offsets. But other airlines purchase offsets themselves instead of expecting travelers to do so (Günther et al., 2020 ).

Carbon offsetting is an important tool in both structural and agentic approaches to tackle aviation emissions. The assumption is that air travel is a pillar of the modern economy and household lifestyles. Even with reduced travel and new technology such as biofuels, aviation emissions will continue. Thus, the industry will need to rely on carbon offsetting to reduce its climate impact. While scholars debate the morality and effectiveness of carbon offsetting (Foerster, 2019 ), it is used in several programs such as Clean Development Mechanisms, Reducing Emissions from Deforestation and Forest Degradation (REDD), and California’s Cap and Trade program (Lovell, 2010 ). For its supporters, the economic logic of offsetting is simple: actors should offset their climate impact instead of canceling these activities because activities generate sufficient value. However, critics point to the difficulty in verifying the climate benefits of offsetting. Scholars attribute travelers’ low take-up of voluntary carbon offsets offered by airlines to credibility problems (Zhang et al., 2019 ). Furthermore, offset programs such as fast-growing forests might inflict collateral damage on the ecosystem by, say, lowering the water table (Jackson et al., 2005 ). Finally, there is a danger that offset users might believe that they have a moral license to pollute and increase their consumption (Günther et al., 2020 )

Agentic approaches to air travel emissions

Individuals can contribute to climate mitigation in three inter-connected capacities: consumers, voters, and influencers. In all these roles, they may influence, intentionally or otherwise, the structures in which they are embedded. Foremost, as consumers, individuals seeking to do the “right thing” inadvertently support political or social issues, low-carbon consumption choices in our case. Scholars have called this “political consumerism” (Stolle and Micheletti, 2013 ) or “ethical consumerism” (Barry and MacDonald, 2018 ). Consequently, firms begin to see a potential for market demand for products with smaller carbon footprints (Roser-Renouf et al., 2016 ). Pro-climate consumers might also serve as activists and influencers seeking to change government and business policies. Individuals could participate in social movements to amplify the climate message embedded in consumption choices. Finally, as voters, individuals might support candidates with pro-climate agendas (De Moor & Verhaegen, 2020 ) who arguably could change policies influencing consumption choices. Voting efforts are hampered by collective action issues when individuals seek to free ride on the efforts of others or when they question the causal efficacy of their vote to shape electoral outcomes (Riker and Ordeshook, 1968 ). However, pro-climate consumption could foster a pro-climate “civic ethic” (Brennan, 2012 ), motivating individuals to overcome their reluctance to vote and help elect pro-climate candidates.

Agentic response to aviation emissions begins with individuals recognizing their culpability in creating them. While individuals with pro-environmental attitudes tend to support governmental action (Stoutenborough et al., 2014 ), would these individuals also curtail their aviation emissions? Alock et al. ( 2017 ) found no association between British respondents’ environmental concerns and their recreational flying decisions. Cocolas et al. ( 2020 ) find that individuals differentiate between the imperative to act on climate concerns when they are at home instead of taking a holiday. In sum, environmental concerns do not necessarily translate into reduced flying.

Why so? Sometimes individuals recognize carbon footprint issues but claim that flying is necessary for them. Higham et al. ( 2014 : 462) call this the flyers’ dilemma: “the tension that exists between the perceived personal benefits of deeply embedded air travel practices and the collective climate change consequences of such practices.” Assuming actors are willing to overcome this dilemma, what should they do? At a minimum, they should reassess their decision to fly and explore alternative mechanisms to address the same task or need. For example, because the Coronavirus pandemic has “normalized” telecommuting for work-related tasks, might this motivate reduced flying in the future? Or individuals might decide to take holidays closer to home instead of flying to far-off destinations.

In the Internet age, individuals face little costs to search for information on the carbon footprint of air travel. There are several carbon calculators on the Web. Travel agencies and airlines provide carbon footprint information (along with offsetting options) when passengers search for tickets. Of course, policy innovations can support individual action. Even when policies do not dictate choices, they can help individuals make the right ones. Consider consumers seeking to buy airline tickets. Towards the end of the purchase, the travel website could inform them of their travel’s carbon footprint and ask if they want to buy offsets. Without this nudge, consumers may not even think of offsets. An even more aggressive strategy would be to make “opt-in” the default option. Here the travel website will automatically include carbon offsets in the ticket price unless the consumer opted out.

Individuals also play the important role of influencing others. For Fragnière ( 2016 ), individuals have a moral duty to serve as influencers irrespective of whether they believe that individual action is causally effective in reducing aggregate emissions. Individuals could do so through a bottom-up approach to change social norms or a top-down approach by lobbying governments and/or firms for more robust climate policies. Households might be more willing to adopt energy conservation measures or install solar panels when they learn that their neighbors have done so (Allcott and Rogers, 2014) . Individuals could also influence their peers through social media and other forms of communication. Of course, not all individuals can aspire to be influencers. Moreover, even individuals with a large network of followers are more legitimate as climate champions when they lead a low-carbon lifestyle (Johnson, 2003 ; Hourdequin, 2010 ; Attari et al., 2019 ).

Individuals may also join a social movement working on reducing aviation emissions (Fragnière, 2016 ), for example, the Extinction Rebellion, Fridays for Future, and Flight Shame. These social movements might eventually encourage pro-climate practices and policy changes (Gössling, et al., 2020 ). As more people join a social movement, individuals might drop their skepticism about the causal efficacy of their actions, motivating higher levels of participation in the movement. As the movement gathers momentum and its “signal” crosses some sort of threshold (Bemmaor, 1984 ; Bolderdijk and Jans, 2021 ), both governments and businesses begin to pay close attention to the movement’s climate demands.

The role of the Flight Shame movement ( flygskam in Swedish) is illustrative because it is creating an anti-flying social norm aimed at consumers, but with spillover effects on governments and the airline industry. Notes the contribution of the Instagram account Aningslösa Influencers (clueless influencers), with over 50,000 followers that shames Instagram members who brag about their air travel. Alongside stigmatizing a social practice, social movements can affirm pro-norm practices. For example, the case of “train brag” ( tågskryt in Swedish) is critical in promoting rail travel.

What are the limitations of any social movement? Does the success of a movement depend on the structural context in which it functions? For example, the flight shame movement seems to be active predominantly in Europe. Is this because Europe has an excellent network of trains and shorter distances which make switching over from flying to trains easier in relation to, say, the USA? Others wonder if some social movements exaggerate problems and provoke overcorrection from individuals. For example, Chiambaretto et al. ( 2021 ) suggest that the “flight shame” movement creates a misleading narrative about the carbon footprint of air travel. Their study of French respondents found that 90% of respondents overestimate air transport’s share in global carbon emissions.

In this review essay, we have examined agentic and structural approaches to tackling the complex issue of aviation emissions. Our framework is summarized in Fig. 1 .

Structural and agentic approaches to reduce aviation emissions

Future research should assess the conditions under which specific approaches are effective in the real world, as opposed to relying on projected reductions based on surveys. Indeed, we found little systematic evidence in the climate policy literature on this count. In part, since early 2020, COVID-19 has disrupted the airline and tourism industry, which has reduced air travel. This means that it is not clear whether reductions in air travel are due to agentic climate action, any specific climate policy governments have implemented, or individuals’ COVID-19 concerns. Once the COVID-19 pandemic is brought under control, scholars should assess the effectiveness of agentic and structural interventions in reducing aviation emissions.

The effectiveness of any approach depends on its political feasibility. Structural approaches are particularly vulnerable on this count. It is not clear if the governments have the political will to aggressively regulate aviation emissions, given the economic disruption such regulations might cause and its equity impacts. While much of the debate on “just transition” has focused on the fossil fuel sector, the airline industry will likely face the same challenges. Much to our surprise, we did not find much literature on this subject, although airlines and the airport ecosystems account for 20 million jobs (ATAG, 2016 ) and economies of many cities hosting major airports crucially depend on air travel (Conventz and Thierstein, 2014 ). Air travel is often crucial for the tourism industry, which supports another 30 million jobs. Future work should focus on just transition issues in the aviation sector and compare them with the debates in the fossil fuel industry.

Might agentic approaches face fewer political hurdles? From an agentic perspective, aviation emissions reflect carbon-intensive lifestyles. Although these are encouraged by rising incomes and government failure to regulate emissions, individuals have considerable autonomy to reduce their carbon footprint (Dietz et al., 2009 ). This is particularly true in airline travel, where individuals (in many cases) could satisfy the same need through lower-emission alternatives (such as trains or telecommuting), without facing a political pushback.

While agentic approaches might face fewer political hurdles, they require individuals to recognize their carbon footprints and act upon them. New policies can increase policy literacy and reduce search costs regarding carbon footprints, thereby motivating them to act. However, even policy-literate individuals might invoke causal inefficacy to justify their continued flying. Social pressure via social movements could create new social norms and motivate consumers to overcome the flyers’ dilemma.

The important lesson is that while individuals exercise autonomy in their consumption decisions and face fewer political hurdles in doing so, institutional innovation can facilitate pro-climate choices. Similarly, individuals can shape some of their embedded structures, especially when they coordinate their consumption choices via social movements. Viewed this way, the agent-structure dichotomy might be less sharp in the long term because under some conditions, agents and structures could exert reciprocal influence on each other (Archer, 1996 ).

What lessons might the airline industry hold for climate mitigation strategies in other sectors, especially in the context of agency-structure debate? Arguably, aviation is an easy case for agentic action because individuals often have choices regarding short-distance travel. Agency-focused approaches of the aviation sector could inform climate politics of the food, where individuals can exercise some level of agency, given the availability of cost-effective substitutes. The issue of reducing meat consumption, especially beef, has become salient in recent years. Individuals are participating in social movements to put pressure on restaurants to offer vegetarian options, including plant-based meat products. The menus of McDonald’s and Burger King include their version of “impossible burgers.” In response to student pressure, some educational institutions have stopped serving meat dishes in their cafeterias. The implication is that strong public pressure is bringing about change without the structural push in the form of public policy such as a meat tax or even a meat ban. On the other hand, agentic interventions might be less successful in the automobile industry. While individuals might be willing to buy electric vehicles (EVs), without a large-scale charging network, drives will face range anxiety and the EV uptake will suffer. Public policy interventions are necessary to establish a network of fast EV charging stations, given the complexity of addressing land use, zoning, and electricity grid regulations. Thus, the level of agentic autonomy to reduce emissions is industry-specific and lessons from the airline case need to be extended thoughtfully.

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Strategy unveiled to achieve carbon-neutral air travel

International flights can transport us to most of the world’s major cities within a day or two and later bring us home — often for less than a thousand dollars per seat.

This jet-setting, however, comes with a heavy carbon emissions cost. Flying coach from Los Angeles to London adds more carbon into the atmosphere than the average lifetime carbon contribution of those living in many of the world’s developing countries.

But in a paper published in iScience , UC Riverside professor Mihri Ozkan and her co-authors unveil a path toward carbon-neutral air travel. The hope lies in e-kerosene, a type of sustainable aviation fuel made by combining carbon dioxide with hydrogen.

E-kerosene can be designed to be chemically identical to conventional jet fuel, said Ozkan, the Climate Action Champion Professor in the Bourns College of Engineering.

“This means it can be used in current aircraft engines and fuel distribution systems without any modifications, making it a practical option for reducing aviation’s carbon footprint,” she said.

Ozkan’s paper envisions a mid-century when large-scale plants powered by solar, wind, and geothermal energy capture carbon dioxide emissions directly from the air. Electricity from the same renewable energy sources can generate hydrogen from water through a process called electrolysis, and the carbon dioxide and hydrogen can then be made into e-kerosene.

While the cost of making e-kerosene is currently around $8 a gallon (more than double the cost of conventional jet fuel), the cost barriers can be overcome through innovation, economies of scale, and government support, she said

E-kerosene production will further benefit from scaling up the production of sustainable jet fuel from biomass , organic materials derived from plants and animals.

“Developing technologies that can process a broader range of feedstocks more efficiently at lower costs is crucial,” Ozkan said. 

Her paper calls for several policy interventions, including financial incentives such as subsidies and tax credits; carbon pricing to narrow the cost gap between sustainable and conventional fuels; sustainable fuel use mandates to create guaranteed markets; investing in infrastructure for the distribution and use of sustainable fuels; support for research and development projects to accelerate innovation; and international collaboration on standards, certification, and incentives.

The paper ’s title is “Forging a Sustainable Sky: Unveiling the Pillars of Aviation E-Fuel Production for Carbon Emission Circularity.” Its co-authors are all associated with the Bourns College of Engineering. They are Anvaya B. Narappa, Thrayesh Namboodiri, Yijian Chai, Matheshwaran Babu, Joan Jennings, Yingfan Gao, Sameeha Tasneem, Jason Lam, Kamal Talluri, Ruoxu Shang, Cengiz S. Ozkan, and Jordyn M. Watkins.

Concerted efforts in technology development and supportive policy measures can make carbon neutral aviation a reality, Ozkan said. We can all stay informed, advocate for sustainable practices, and support policies that encourage the development and adoption of sustainable fuels, she added.

“It's a journey toward a more sustainable future where flying doesn't have to come with a heavy carbon footprint,” Ozkan said. “As long as there is access to renewable electricity, water, and CO2, e-kerosene can be produced, making it a highly scalable solution to meet the aviation industry's fuel demands.”  

Cover image by Mihri Ozkan/UCR

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KPMG's carbon emissions rose 4% in 2023

KPMG International hit some turbulence on its mission to reach net-zero carbon emissions by 2030. 

"Our Impact Plan" report . The firm credits the uptick to the return of business travel since the COVID-19 pandemic. 

KPMG's air travel emissions increased 77% year-over-year, and "other" business travel emissions increased by approximately 37%. Looking at gross emissions by region, Europe, the Middle East and Africa accounted for a 38% increase. Meanwhile, the Americas and Asia Pacific decreased their gross emissions by roughly 19% and 8%, respectively.

Despite the increase, the firm has still seen a 40% overall decrease in air travel emissions compared to its 2019 baseline, and its gross emissions have declined 22% since then.

"The rise in air travel is principally due to our people beginning to reconnect with client and team members following post-COVID-19 travel restrictions as well as organizational growth and a change in emissions factors," the report reads. "Due to proactive travel management, the implementations of sustainable travel guidelines across KPMG firms, and the behavior-changing influence of our ICP, this 'rebound' in air travel has not brought us back to pre-pandemic levels."

Positively, KPMG reduced its total electricity usage and grew its proportion of renewable energy across the organization from 79% to 81%. The firm credits these results to the continuation of hybrid work and initiatives by its firms to improve energy efficiency. It aims to be using 100% renewable energy by 2030. 

voluntary carbon markets . 

"We are striving to take an integrated and coordinated approach across our KPMG firms to reduce our impacts and develop the most sustainable footprint possible," John McCalla-Leacy, head of global ESG at KPMG International, said in the report. "We also want to maximize our impact by helping clients on their decarbonization journeys — which bring not only risk but huge opportunity. We're acting ourselves and helping others act — we are all in it together as we move along this path."

reporting by the International Consortium of Investigative Journalists.

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10 Travel Mistakes That Are Increasing Your Carbon Footprint

T ravel provides an exciting opportunity to explore different cultures, taste new cuisines and make long-lasting memories. With rising concerns about climate change, however, it’s important to be mindful of the impact our vacations have on the environment.

Travelers are often unaware of the carbon footprint associated with their choices of lodging, activities, transit and more. Throughout a given trip, a combination of big and small decisions can contribute significantly to the total volume of greenhouse gas emissions.

We asked travel and environmental experts to share some common mistakes travelers make that increase their carbon footprints. Read on to learn what they are (along with some advice for offsetting these behaviors).

Taking indirect flights

“Flying will be the main contributor to the carbon footprint from most vacations,” said Tom Hall, vice president of Lonely Planet . “While in a lot of cases there isn’t an alternative, travelers can look to minimize the number of flights they take, use newer, less polluting aircraft and, once in a destination, use cleaner ground transportation such as trains.”

Basically, you want to spend as little time in the air as possible. Flying directly rather than taking connecting flights also means lower emissions, because the rate of fuel usage is higher during takeoff and landing compared to cruising.

“One of the biggest mistakes revolves around not considering the length of travel time when securing airfare,” said Brian Mullis, founder of Sustainable Travel International . “Longer, less convenient, indirect flights are often cheaper but have a larger carbon footprint.”

Overpacking

“A mistake that we often make and aren’t always aware of the consequence is overpacking,” said Paula Espinoza, creative director at  Naya Traveler . “This can increase the weight of luggage and, in turn, increase the fuel consumption of transportation. An easy fix is planning your outfits and what will be necessary for your trip ahead of time. This way, you’ll avoid packing unnecessary items.”

Heavier luggage on a flight means the plane consumes more fuel, so try to stick to the essentials. Limiting your load to carry-ons also reduces your luggage’s environmental footprint, as checked bags must undergo a more energy-intensive process with all the conveyer belts and luggage carts.

Flying when trains and buses are options

“Some of the best ways to minimize your footprint go hand-in-hand with enjoying a more authentic experience,” noted Brian McMahon, travel curator at Origin . “The biggest one is avoiding flights whenever possible, so maybe instead of flying all over Europe on your next trip, really get to know one or two countries by train. Not only are you avoiding the huge carbon emissions that come from air travel, but you’re also supporting local communities by spreading the benefits of tourism to lesser-visited destinations.”

Prioritize taking trains and buses when you can. You’ll get the chance to see the countryside and enjoy the scenery along the way. 

“One long-haul flight is the same as driving a car for a whole year ,” said  Rachel Dodds , a sustainable travel expert and professor at Toronto Metropolitan University’s Ted Rogers School of Hospitality and Tourism Management. “If you can avoid flying, then do so ― especially in places like Europe where rail is amazing and it is easy to avoid flying.”

At the same time, there are cases where flying actually isn’t the least efficient option. 

“If you are traveling solo, sometimes a long-haul plane flight will give you a lower carbon footprint than driving the same long distance,” said Rebecca Benner, deputy director of the global climate team at the Nature Conservancy . “That said, if you are traveling with more than one to two people, driving is always going to lower your carbon footprint ― and a much lower one if the vehicle is hybrid or electric.”

Try to use public transit to get around once you’re at your destination, as well. If you have to rent a car, aim for a fuel-efficient vehicle.

Not eating or shopping locally

“Being conscious of where you eat when you are traveling can have an impact on one’s carbon footprint and environmental impact in general,” Benner said. “Look for restaurants with locally sourced products ― ideally all locally sourced ― or ‘farm to table’-type restaurants. Eating local means [that] foods don’t have to travel so far ― travel being what usually increases carbon footprint. In addition, buying local supports the local economy.”

Prioritize plant-based delicacies, as the meat industry accounts for a large amount of global greenhouse gas emissions. 

“Dining low on the food chain  and eating locally available foods are ways to reduce our individual footprint,” said Kelly Bricker, director of the Center for Sustainable Tourism at Arizona State University. “Rethinking how we can contribute back, purchasing locally, supporting local businesses and utilizing modes of sustainable transportation can all assist in reducing one’s carbon footprint.”

Try to buy locally made souvenirs when possible, rather than mass-produced products that were clearly shipped from far away. 

“Be a curious customer,” advised Charlie Cotton, founder of the carbon consultancy  Ecollective . “If you are spending hundreds or thousands of dollars with a company, you have a right to ask what is the carbon footprint of what you have bought. It has a massive ripple effect through the company, as they realize they can’t but really should be able to answer it.”

Booking business class

“Many may not realize this, but your cabin class can make a difference on your carbon footprint,” said Per Christiansen, senior vice president for EMEA and APAC marketing at Kayak, a travel search engine and booking site.

Christiansen recommended his site’s  CO2 feature , which calculates flight emissions based on factors like travel class, aircraft type, cargo capacity and more.

“It cuts down your flight footprint to book economy, rather than business class seats, which can double a passenger’s air travel footprint since they take up twice as much space,” said Kaitlyn Brajcich, senior manager of communications and training at Sustainable Travel International . “While airlines are starting to transition towards more fuel-efficient aircraft and sustainable aviation fuels, these technologies must be drastically scaled up before they will be able to be widely adopted.”

Choosing hotels that are not eco-friendly

“The place you choose to stay on your trip can also impact your carbon footprint,” Benner said. “There are a growing number of hotels that are focused on using high-efficiency lights and appliances, being thoughtful about how often rooms need to be cleaned and sourcing food from local places. Staying at these hotels will lower your carbon footprint.”

You may have to do some research, but there are certification programs that can help you identify hotels that are more or less eco-friendly. One popular example is the global Leadership in Energy and Environmental Design building program.

“A common misconception around carbon is that cute-looking island hotels often have a much higher carbon footprint than you may expect,” Cotton said. “This is because they often need a diesel generator to power their electricity. A classic example is many of the Maldives hotels.”

Seek out accommodations that prioritize renewable energy sources, water conservation and waste reduction. 

Requesting daily hotel cleanings

“A surprising contributor to your carbon footprint might be staying at hotels that do clean your room every day,” Benner said. “Washing and drying sheets and vacuuming daily adds quite a lot to your carbon footprint.”

Following the onset of the pandemic, many hotels made daily cleanings optional, and this policy is still in effect at plenty of places. When you check into the hotel, you can ask that your room be skipped, or make use of your “do not disturb” sign.

Leaving the AC on in your room

“One common mistake that travelers make, particularly in hot climates, is leaving on the air conditioning when they leave the room,” Brajcich said. “All day while the AC is cooling an empty room, it is also generating carbon emissions. Turning off the AC every time they leave the room, or turning on the fan instead when they are in the room, is a simple way that travelers can avoid needless emissions.”

If you’re concerned about heat, close the curtains to keep the sun from beaming in all day. Do your best to turn off the lights, TV and other electronics when they aren’t in use to reduce energy consumption. Take shorter showers and reuse your towels. 

“Avoid wasting water, particularly in drought-prone areas,” said Anna Decam, environment program manager at the Sustainable Hospitality Alliance . “Use a reusable water bottle, engage in local recycling and composting schemes, and protect local habitats from pollution and litter.”

Choosing activities and tour operators that aren’t eco-friendly

“Choosing sustainability-focused accommodations, tour operators, transport providers and dining experiences can also help to minimize our travel emissions,” said writer and sustainable travel expert  Sarah Reid .

Avoid engaging in activities that can be harmful to the environment, like trophy hunting, motorized water sports and visits to exploitative animal parks. Instead, focus on hiking, biking and swimming, and try to pursue itinerary items that promote conservation.

“Look out for tourism activities which support local communities and businesses, as well as respecting nature,” Decam said.  

Once you arrive at your destination, think outside the box and seek out events and experiences that give back to the Earth while allowing you to explore a new place. 

“You can volunteer to do beach or park cleanup, go on a plant medicine walk, go in nature and leave no trace, visit a permaculture farm, exchange seeds and goods in a trade circle, [and] support and commune with botanical gardens that also preserve genetic diversity and heirloom varieties,” suggested Eloisa Lewis, the founder of New Climate Culture .

Spreading your travel across multiple short trips

“ Nearly half of tourism’s carbon footprint comes from transportation alone,” Brajcich said. “In general, air travel tends to be the most carbon-intensive mode of travel. One way that travelers can cut down air travel emissions is by taking one longer trip each year, rather than multiple shorter trips.”

In the same vein, consider embracing the “slow travel” approach and spending mindful quality time in a smaller number of destinations, rather than trying to jam-pack your itinerary with as many countries and cities as you can get to.

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Jet scandal: Climate minister urged to consider carbon emissions after RAAF flight controversy

The PM and two of his senior ministers have been urged to do one thing after coming under fire for using two private jets to fly to the same event.

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Anthony Albanese has been urged to offset emissions from his controversial jet use after it was revealed that he and two ministers chartered two private planes to attend the same clean energy event in the NSW Hunter Valley.

Mr Albanese, Climate Change and Energy Minister and Industry and Science Minister Ed Husic all flew to the region from Canberra on Thursday to announce a $1bn to support Australian manufacturing in solar technology.

After it emerged that the politicians and their staff flew separately in two separate Royal Australian Air Force jets, Teal MP Zali Steggall urged the leaders to compensate for the carbon emitted for the trip.

“I certainly hope they were offsetting the emissions of those two jets with companies, like Green fleet and other places like that where you can offset the emissions of your travel,” Ms Stegall told Seven’s Sunrise.

“I certainly hope and I call on the Minister for Climate Change to do that. Look, as a lowly independent, we don’t get the luxuries of flying in the ADF jets.”

Private jets have a dramatically higher carbon footprint per passenger than commercial planes, with the average private jet emitting two tonnes of carbon an hour.

According to a 2021 report from the European Federation for Transport and Environment private jets are five to 14 times more polluting per passenger than commercial flights, and 50 times more polluting than trains.

Mr Bowen said the use of two private jets was a decision made by the airforce for safety reasons.

“The Prime Minister has a large jet available to him and that would normally be what we take,” he said on Monday.

“The runway at Scone wasn’t strong enough to take a large jet so the air force … decided for two jets.”

Speaking later on Wednesday, Labor frontbencher Katy Gallagher said that there was nothing unusual about the trip.

“PMs have to travel around the country - it’s part of their job,” senator Gallagher told reporters.

And I think what people will remember is that they’ve got a very hardworking prime minister who’s out there everyday looking to expand economic opportunities,” she said.”

Opposition transport spokeswoman Bridget McKenzie said the government should consider “jet pooling”

“I fail to see why these guys, when they’re leaving from the same place on the same day, within 30 minutes of each other, couldn’t have either shared the plane or indeed, some of them, if they couldn’t all fit, use the commercial options that were available to them to fly direct from Canberra to Newcastle to make the announcement,” Senator McKenzie said.

“It’s quite incredible.”

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What’s the Carbon Footprint of March Madness?

March Madness means 68 teams vying to become champion, Cinderella runs for a few underdogs and big business for the NCAA, which earns 85% of its annual operating budget during the men’s basketball tournament.

But all of that comes at a tremendous cost: An estimated 463 million pounds (210 million kilograms) of carbon dioxide equivalent emissions are released into the atmosphere during the three-week event . That’s similar to all the emissions of a large university – such as 2019 champion University of Virginia – for an entire year.

These greenhouse gas emissions warm the planet, contributing to heat waves, sea level rise and extreme weather. Carbon dioxide equivalent is a way of measuring the impact of several different greenhouse gases at once.

Crunching carbon for large-scale event

A colleague, Alex Cooper , and I came up with this figure based on data for the 2019 NCAA Tournament.

Past research on the carbon footprint of sporting events has primarily focused on one-city events, such as the Football Association Challenge Cup in the U.K. and centralized events like the Olympics . Little prior research has sought to determine the environmental impact of a large-scale sporting event like the NCAA’s men’s basketball tournament.

In addition, when sports organizers do calculate and report emissions for their events, they typically only report what happens at their facility during the event. They don’t consider the environmental impact, for example, of travel to and from the event.

So, we wanted to know, what’s the carbon tally for a huge and popular event like March Madness?

For our peer-reviewed study , which was published in October 2021 in the Journal of Cleaner Production, we aimed to estimate the carbon emissions for all the activities that go into running a massive basketball tournament that takes place in multiple cities across the country in a short span of time. While our estimates are based on 2019, we believe that tournament-generated emissions are comparable to other years, including 2023.

We looked beyond facilities to consider team and fan flight and automobile travel, facility operations, food consumption, waste generation and lodging for everyone based on each team’s progression through the 2019 tournament. We used attendance estimates to determine the impact of hotel stays , fan and team air and automobile travel, waste generation , food consumption and sport facility operations to form our carbon emission model.

Based on our model, we found that this resulted in 463 million pounds of CO2 equivalent emissions. That’s about 1,100 pounds (499 kilograms) for every player, coach and fan who attends. That amount is the same as driving over 1,200 miles (1,930 kilometers) in a typical sedan .

The biggest source of emissions by far was, as you might expect, fan and team travel, which accounted for about 79.95% of the total. The next-largest was hotel stays at 6.83%, followed by food at 6.37%, stadium operations at 5.9% and general waste at 0.95%.

What surprised us most was that the category of travel as a share of the total was lower than in previous studies that analyzed the carbon footprint of sporting events. But that was primarily because, unlike in those other studies, we considered many other aspects of the event, such as lodging, food and waste.

Ways to mitigate impact

So what can the organizers of March Madness – or any tournament, really – do to reduce the carbon footprint?

Since travel makes up so much of that footprint, targeting emissions from long-distance travel, such as flights, may be one of the most effective ways to lower the event’s overall impact, as other researchers have noted .

While travel can’t be completely eliminated for a tournament like the NCAA’s, organizers could consider more regional placements to reduce the distances fans and teams must travel. For example, in 2019, Mississippi State, Liberty, Virginia Tech, Saint Louis and Wisconsin all traveled to San Jose, California. The idea would be for more games to take place regionally to decrease travel distances. This would not only reduce carbon emissions but could also increase profits by making it easier for more fans to attend.

And when evaluating host cities and sites, the NCAA could consider local policies that encourage sustainable hotel operations. For example, during the 2019 tournament, California host sites had more energy-efficient hotel operations , thus reducing the second-highest contributor to overall emissions. The same could be said about selecting arenas and sport facilities that are energy efficient.

This article is republished from The Conversation under a Creative Commons license. Read the original article .

Brian P. McCullough, Associate Professor of Sport Management and Director, Center for Sport Management and Education and the Laboratory for Sustainability in Sport, Texas A&M University.

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Sensor network shows EVs are reducing CO2 emissions in the Bay Area. Is it enough?

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A network of air monitors installed in Northern California has provided scientists with some of the first measurable evidence quantifying how much electric vehicles are shrinking the carbon footprint of a large urban area.

Researchers from UC Berkeley set up dozens of sensors across the Bay Area to monitor planet-warming carbon dioxide, the super-abundant greenhouse gas produced when fossil fuels are burned.

Aggressive and impactful reporting on climate change, the environment, health and science.

Between 2018 and 2022, the region’s carbon emissions fell by 1.8% each year, which the Berkeley researchers concluded was almost exclusively owed to drivers switching to electric vehicles, according to a study published Thursday in the journal Environmental Science & Technology.

In that time, Californians purchased about 719,500 zero-emission or plug-in hybrid vehicles, more than triple the amount compared to the previous five years, according to the California Department of Energy . The Bay Area also had a higher rate of electric vehicle adoption than the state as a whole.

While the findings confirm the state’s transition to zero-emission vehicles is substantially lowering carbon emissions, it also reveals these reductions are still not on pace to meet the state’s ambitious climate goals .

Emissions need to be cut by around 3.7% annually, or nearly twice the rate observed by the monitors, according to Ronald Cohen , UC Berkeley professor of chemistry. Although cars and trucks are the state’s largest source of carbon emissions, it underscores the need to deploy zero-emission technology inside homes and for the power grid .

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“I think what we see right now is evidence of strong success in the transportation sector,” Cohen said. “We’re going to need equally strong success in home and commercial heating, and in the [industrial] sources. We don’t yet see significant movement in those, but policy pushing on those is not as far ahead as policy on electric vehicles.”

Although cities only cover roughly 3% of global surface area, they produce about 70% of carbon emissions. Urban monitoring networks could give policymakers a more granular view of the sources of pollution.

Los Angeles and other major cities have set up Cohen’s monitors in hopes it could reveal more insights about carbon emissions and air pollution .

As government agencies continue to assess efforts to decarbonize the economy through socioeconomic data and computer models, experts argue that monitoring networks like Berkeley’s could provide a sorely needed reality check for some communities and offer another tool to verify the effectiveness of climate policies.

“I think the best contribution this makes is showing how we can check what’s going on,” said Danny Cullenward , a climate economist and senior fellow at the Kleinman Center for Energy Policy at the University of Pennsylvania. “It’s probably not the last word. But it’s an elegant way to ground-truth some of these things. We need more of these approaches, not fewer.”

These systems could also reveal blind spots. California, for example, doesn’t account for greenhouse gases leaking out of unplugged oil wells or carbon emissions from biofuels, such as power plants that burn woody waste.

“The atmosphere doesn’t care,” Cullenward said. “You can still measure it.”

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The largest deterrent to installing such networks is funding. But the equipment has become more inexpensive over the years: Each of the Berkeley sensors costs less than $10,000.

But the intention, Cohen said, is not to replace the current modes of climate accounting. He hopes those methods and his will work together.

“We’re not suggesting that you do one in the absence of the other, but that they are stronger together.”

Toward a more sustainable California

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Tony Briscoe is an environmental reporter with the Los Angeles Times. His coverage focuses on the intersection of air quality and environmental health. Prior to joining The Times, Briscoe was an investigative reporter for ProPublica in Chicago and an environmental beat reporter at the Chicago Tribune.

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