UK government targets for “sustainable aviation fuels” (SAFs) will only cut emissions from the sector to 0.8% below current levels in 2040, Carbon Brief analysis shows.
From 2025, flights taking off from the UK must use a fixed share of SAFs, which are largely made from waste products. This share will gradually rise from 2% next year to 22% in 2040.
The government says its “SAF mandate” will cut aviation emissions by 6.3m tonnes of carbon dioxide equivalent (MtCO2e) in 2040.
However, Carbon Brief analysis of government forecasts shows this being almost entirely wiped out by rising demand for air travel, meaning emissions would only fall by 0.8% overall.
The SAF mandate is the most substantial policy to date under the UK government’s “jet-zero” strategy for decarbonising air travel, which eschewed efforts to limit demand. The mandate relies heavily on fuels made from used cooking oil and other waste products, which are in limited supply.
No change
The SAF mandate will require jet fuel suppliers to ensure that an increasing share of the product they supply is “sustainable”. This is meant to encourage investment in new facilities to produce SAFs.
Fuels described as SAFs include those made from waste, such as used cooking oil, household waste and offcuts from the forestry sector.
Despite their name, SAFs produce just as many emissions as fossil fuels when burned to power planes.
However, they generally – although not always – have a lower overall “lifecycle” carbon footprint than petroleum-based jet fuel. This is due to CO2 emissions absorbed from the atmosphere when growing plants for biofuels, or emissions that are avoided by diverting waste products to be used as fuels.
These emissions savings are counted towards the UK’s aviation sector as a whole.
(The government says that, for the time being, it will not support SAFs made directly from crops, which tend to have relatively high carbon footprints due to changes in land use.)
The new UK mandate starts in 2025 with a requirement that 2% of total jet fuel demand is SAF, increasing to 10% in 2030 and 22% in 2040. The government says there is currently not enough certainty in the SAF market to set targets beyond that date.
These measures will cut overall aviation emissions by 2.7MtCO2e in 2030 and 6.3MtCO2e in 2040, according to the government.
Based on government forecasts for jet fuel use, this change will be almost totally offset by a growth in flights, leaving UK aviation emissions virtually unchanged between now and 2040.
Emissions in 2025 are expected to be 36.0MtCO2e, while 15 years later they are set to be 35.7MtCO2e, according to Carbon Brief analysis. This is a drop of just 0.3MtCO2e, or 0.8%. This is illustrated in the chart below, with the SAF mandate merely preventing an increase in emissions resulting from higher jet fuel use in 2040.
These figures are derived from the government’s “central case”, cited in its underlying analysis for the SAF mandate, which sees jet fuel use increasing from 11.5m tonnes (Mt) in 2025 to 13.3Mt in 2040. This, in turn, is based on policies in the government’s “continuation of current trends” scenario, with the SAF mandate included.
The government expects far more flights to take off from the UK in the coming years, resulting in higher jet fuel use. It has resisted pressure to curb the demand for air travel, despite warnings from experts that such actions are vital for reducing aviation emissions.
In its jet-zero strategy, the government stated that it is aiming for a “high ambition” scenario, which would see aviation emissions fall faster in the coming years. However, as it stands, it has not introduced policies to drive further emissions reductions in planes.
The SAF mandate assumes that SAFs reduce lifecycle emissions from jet fuel by 70%. Certificates will be issued to fuel suppliers for each tonne of SAF produced, using this baseline emissions reduction goal as the standard.
However, Prof Bill Rutherford, an Imperial College London biochemist who contributed to two major assessments of low-carbon aviation fuels in the UK last year, tells Carbon Brief he is sceptical about lifecycle emissions analysis that shows such high emissions benefits:
“Lifecycle analysis is a very fuzzy science…You can basically get what you want out of it.”
For example, in its analysis, the government assumes that SAFs made from used cooking oil – which are expected to make up virtually the entire UK supply in the short-term – cut lifecycle emissions by roughly 95-98% compared to conventional jet fuel.
Dr Andrea Fantuzzi, another Imperial College London chemist who also worked on the low-carbon fuel assessments with Rutherford, says such figures seem “way too high”. He estimates that the savings would be closer to 70%.
Fantuzzi adds that even this does not account for the land originally used to produce the oil, and assumes that the oil would otherwise be thrown away – rather than used to power road vehicles, for example. (For more on waste oils, see: More cooking oil.)
Additionally, Rutherford points out that the use of SAFs has no impact on non-CO2 emissions from planes, which could account for up to two-thirds of their climate impact. He concludes:
“The only way you can make aviation any more sustainable is to do less of it.”
More cooking oil
The only SAFs that are currently available in the UK are fuels made from used cooking oil and other waste oils, which are collected from restaurants and factories.
However, the SAF mandate includes a limit on the amount of waste oil-based fuels within its overall targets. This is partly to “incentivise the development of new technologies” and partly due to concerns that waste oil supplies will be insufficient.
For the first two years, these fuels will be allowed to make up 100% of UK SAFs. This then falls to 71% in 2030 and 33% in 2040. Overall, waste oil-based SAFs would account for 2% of total jet fuel use in 2025 and up to 7.8% in 2040.
Despite these limits, waste oil-based SAF use is expected to rise around 15-fold from current levels within a decade. This huge increase in demand for waste cooking oil under the SAF mandate is illustrated in the figure below.
The Aviation Environment Federation said in a statement that the amount of waste oil being allowed into UK jet fuel under the UK’s SAF mandate is “much higher than we, and many others, were expecting, and appears to be the result of airline pressure”. The looser cap on these fuels was “welcomed” by industry body Airlines UK.
It raises the question of where the UK will source the required volume of waste oil to meet SAF targets.
Studies have shown that there is nowhere near enough waste cooking oil produced domestically, within the UK, to supply jet fuel demand. “We’re not about to start eating more chips, so we will have to start importing more waste oil,” Matt Finch, UK policy manager at the NGO Transport and Environment, tells Carbon Brief.
The government itself acknowledges this, saying that production of these SAFs within the UK is likely to be constrained by the availability of waste cooking oil from 2029 onwards.
It notes that their availability will therefore be “highly dependent” on how much waste oil the UK can import.
As of 2023, waste cooking oil collected in the UK only accounted for 7% of the country’s SAF production. This share has shrunk in recent years, such that imports from other countries – particularly China – have driven most of the growth in production, as the chart below shows.
There is mounting evidence that the demand for imported cooking oil in the UK and Europe is being met with virgin palm oil that has been fraudulently passed off as waste. This would cancel out the fuel’s emissions savings, due to the land clearances for oil palm plantations.
The UK’s aviation sector will have to compete not only with other countries for a limited pool of waste cooking oil, but also with other sectors.
Most of the UK’s waste cooking oil supplies are currently used to make biofuels for trucks and other road transport. Again, diverting resources from road fuel use would undermine the emissions savings from using them in SAFs.
The government acknowledges this, noting that “the SAF mandate may divert feedstocks which would have been utilised in other sectors of the economy and this may increase emissions in other sectors”. However, it says this is justified because “there are limited alternatives to decarbonise aviation by 2050”.
One of the scenarios modelled by the government assumes that SAF targets are met, but insufficient waste cooking oil means there is not enough biodiesel for road vehicles. This reduces the cumulative emissions savings between 2025-40 from 53.9MtCO2e to 43.0MtCO2e.
New fuels
The government is also supporting new types of SAF production in the UK, including fuels made from “black bin bag waste” and residues from farming or forestry.
In the newly released documents, the government says the UK will be a “leader” and a “first mover” in these technologies, spurred on by the cap on waste oil fuels and supported by the Advanced Fuel Fund.
Unlike waste oil-based fuels, the government says there will be “sufficient” materials available to meet production demand for these advanced fuels until at least 2040. From that point onwards, it says lack of materials “may become a constraining factor”.
However, a 2023 report by the Royal Society highlighted the limited availability of some waste materials to produce SAFs. It estimated that forest offcuts, for example, would be able to provide no more than 1.7% of current jet fuel demand.
Moreover, many waste sources are already recycled or burned to generate electricity and the government has targets in place to cut household waste in the coming years. “Most waste is already used for something that’s not jet fuel, so we know supplies of waste-based SAF will be limited,” Finch tells Carbon Brief.
Finally, the government’s mandate also includes another target, within the overarching SAF goal, for scaling up the production of “power-to-liquid” fuels.
These fuels can be made using green hydrogen and carbon captured from the air. Unlike most SAFs, they could cut up to 100% of CO2 emissions compared to conventional jet fuel, but they are currently less developed than other options.
The target for power-to-liquid fuels will start in 2028 at 0.2% of total jet fuel demand, reaching 0.5% in 2030 and 3.5% in 2040.
These targets are lower than the ones introduced in the EU, which is aiming for 35% of its jet fuel to be power-to-liquid by 2050. The bloc is also targeting 70% of aviation demand to be met with SAFs by 2050, whereas the UK’s targets stop at 22% by 2040.
In its “balanced net-zero pathway” for UK aviation, government advisors the Climate Change Committee (CCC) proposed that SAFs should make up 25% of jet fuel by 2050, with one-third of this made up of power-to-liquid fuels – roughly 8% of total jet fuel. The government targets are roughly in line with this trajectory.
Thinktank Green Alliance laid out three scenarios for SAF expansion in 2022, including higher ambition goals, with power-to-liquid fuels reaching 28% and 50% of total jet fuel by 2050.
However, it noted that such a rollout could be constrained by the large amounts of additional green hydrogen and renewable power required to produce these fuels.
The report stated:
“It could be argued that aviation should not be a priority use of renewables as there are other options to cut carbon in the sector, such as managing the number of flights taken.”
The post Analysis: Benefits of UK ‘sustainable aviation fuel’ will be wiped out by rising demand appeared first on Carbon Brief.
Analysis: Benefits of UK ‘sustainable aviation fuel’ will be wiped out by rising demand
N.C. Gov. Josh Stein wants state lawmakers to rethink tax breaks for data centers. The industry’s opacity makes it difficult to evaluate costs and benefits.
Tax breaks for data centers in North Carolina keep as much as $57 million each year into from state and local government coffers, state figures show, an amount that could balloon to billions of dollars if all the proposed projects are built.
The Global Environment Facility (GEF), a multilateral fund that provides climate and nature finance to developing countries, has raised $3.9 billion from donor governments in its last pledging session ahead of a key fundraising deadline at the end of May.
The amount, which is meant to cover the fund’s activities for the next four years (July 2026-June 2030), falls significantly short of the previous four-year cycle for which the GEF managed to raise $5.3bn from governments. Since then, military and other political priorities have squeezed rich nations’ budgets for climate and development aid.
The facility said in a statement that it expects more pledges ahead of the final replenishment package, which is set for approval at the next GEF Council meeting from May 31 to June 3.
Claude Gascon, interim CEO of the GEF, said that “donor countries have risen to the challenge and made bold commitments towards a more positive future for the planet”. He added that the pledges send a message that “the world is not giving up on nature even in a time of competing priorities”.
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Donors under pressure
But Brian O’Donnell, director of the environmental non-profit Campaign for Nature, said the announcement shows “an alarming trend” of donor governments cutting public finance for climate and nature.
“Wealthy nations pledged to increase international nature finance, and yet we are seeing cuts and lower contributions. Investing in nature prevents extinctions and supports livelihoods, security, health, food, clean water and climate,” he said. “Failing to safeguard nature now will result in much larger costs later.”
At COP29 in Baku, developed countries pledged to mobilise $300bn a year in public climate finance by 2035, while at UN biodiversity talks they have also pledged to raise $30bn per year by 2030. Yet several wealthy governments have announced cuts to green finance to increase defense spending, among them most recently the UK.
As for the US, despite Trump’s cuts to international climate finance, Congress approved a $150 million increase in its contribution to the GEF after what was described as the organisation’s “refocus on non-climate priorities like biodiversity, plastics and ocean ecosystems, per US Treasury guidance”.
The facility will only reveal how much each country has pledged when its assembly of 186 member countries meets in early June. The last period’s largest donors were Germany ($575 million), Japan ($451 million), and the US ($425 million).
The GEF has also gone through a change in leadership halfway through its fundraising cycle. Last December, the GEF Council asked former CEO Carlos Manuel Rodriguez to step down effective immediately and appointed Gascon as interim CEO.
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New guidelines
As part of the upcoming funding cycle, the GEF has approved a set of guidelines for spending the $3.9bn raised so far, which include allocating 35% of resources for least developed countries and small island states, as well as 20% of the money going to Indigenous people and communities.
Its programs will help countries shift five key systems – nature, food, urban, energy and health – from models that drive degradation to alternatives that protect the planet and support human well-being by integrating the value of nature into production and consumption systems.
The new priorities also include a target to allocate 25% of the GEF’s budget for mobilising private funds through blended finance. This aligns with efforts by wealthy countries to increase contributions from the private sector to international climate finance.
Niels Annen, Germany’s State Secretary for Economic Cooperation and Development, said in a statement that the country’s priorities are “very well reflected” in the GEF’s new spending guidelines, including on “innovative finance for nature and people, better cooperation with the private sector, and stable resources for the most vulnerable countries”.
Aliou Mustafa, of the GEF Indigenous Peoples Advisory Group (IPAG), also welcomed the announcement, adding that “the GEF is strengthening trust and meaningful partnerships with Indigenous Peoples and local communities” by placing them at the “centre of decision-making”.
The post GEF raises $3.9bn ahead of funding deadline, $1bn below previous budget appeared first on Climate Home News.
GEF raises $3.9bn ahead of funding deadline, $1bn below previous budget
Tropical cyclones that rapidly intensify when passing over marine heatwaves can become “supercharged”, increasing the likelihood of high economic losses, a new study finds.
Such storms also have higher rates of rainfall and higher maximum windspeeds, according to the research.
The study, published in Science Advances, looks at the economic damages caused by nearly 800 tropical cyclones that occurred around the world between 1981 and 2023.
It finds that rapidly intensifying tropical cyclones that pass near abnormally warm parts of the ocean produce nearly double – 93% – the economic damages as storms that do not, even when levels of coastal development are taken into account.
One researcher, who was not involved in the study, tells Carbon Brief that the new analysis is a “step forward in understanding how we can better refine our predictions of what might happen in the future” in an increasingly warm world.
As marine heatwaves are projected to become more frequent under future climate change, the authors say that the interactions between storms and these heatwaves “should be given greater consideration in future strategies for climate adaptation and climate preparedness”.
‘Rapid intensification’
Tropical cyclones are rapidly rotating storm systems that form over warm ocean waters, characterised by low pressure at their cores and sustained winds that can reach more than 120 kilometres per hour.
The term “tropical cyclones” encompasses hurricanes, cyclones and typhoons, which are named as such depending on which ocean basin they occur in.
When they make landfall, these storms can cause major damage. They accounted for six of the top 10 disasters between 1900 and 2024 in terms of economic loss, according to the insurance company Aon’s 2025 climate catastrophe insight report.
These economic losses are largely caused by high wind speeds, large amounts of rainfall and damaging storm surges.
Storms can become particularly dangerous through a process called “rapid intensification”.
Rapid intensification is when a storm strengthens considerably in a short period of time. It is defined as an increase in sustained wind speed of at least 30 knots (around 55 kilometres per hour) in a 24-hour period.
There are several factors that can lead to rapid intensification, including warm ocean temperatures, high humidity and low vertical “wind shear” – meaning that the wind speeds higher up in the atmosphere are very similar to the wind speeds near the surface.
Rapid intensification has become more common since the 1980s and is projected to become even more frequent in the future with continued warming. (Although there is uncertainty as to how climate change will impact the frequency of tropical cyclones, the increase in strength and intensification is more clear.)
Marine heatwaves are another type of extreme event that are becoming more frequent due to recent warming. Like their atmospheric counterparts, marine heatwaves are periods of abnormally high ocean temperatures.
Previous research has shown that these marine heatwaves can contribute to a cyclone undergoing rapid intensification. This is because the warm ocean water acts as a “fuel” for a storm, says Dr Hamed Moftakhari, an associate professor of civil engineering at the University of Alabama who was one of the authors of the new study. He explains:
“The entire strength of the tropical cyclone [depends on] how hot the [ocean] surface is. Marine heatwave means we have an abundance of hot water that is like a gas [petrol] station. As you move over that, it’s going to supercharge you.”
However, the authors say, there is no global assessment of how rapid intensification and marine heatwaves interact – or how they contribute to economic damages.
Using the International Best Track Archive for Climate Stewardship (IBTrACS) – a database of tropical cyclone paths and intensities – the researchers identify 1,600 storms that made landfall during the 1981-2023 period, out of a total of 3,464 events.
Of these 1,600 storms, they were able to match 789 individual, land-falling cyclones with economic loss data from the Emergency Events Database (EM-DAT) and other official sources.
Then, using the IBTrACS storm data and ocean-temperature data from the European Centre for Medium-Range Weather Forecasts, the researchers classify each cyclone by whether or not it underwent rapid intensification and if it passed near a recent marine heatwave event before making landfall.
The researchers find that there is a “modest” rise in the number of marine heatwave-influenced tropical cyclones globally since 1981, but with significant regional variations. In particular, they say, there are “clear” upward trends in the north Atlantic Ocean, the north Indian Ocean and the northern hemisphere basin of the eastern Pacific Ocean.
‘Storm characteristics’
The researchers find substantial differences in the characteristics of tropical cyclones that experience rapid intensification and those that do not, as well as between rapidly intensifying storms that occur with marine heatwaves and those that occur without them.
For example, tropical cyclones that do not experience rapid intensification have, on average, maximum wind speeds of around 40 knots (74km/hr), whereas storms that rapidly intensify have an average maximum wind speed of nearly 80 knots (148km/hr).
Of the rapidly intensifying storms, those that are influenced by marine heatwaves maintain higher wind speeds during the days leading up to landfall.
Although the wind speeds are very similar between the two groups once the storms make landfall, the pre-landfall difference still has an impact on a storm’s destructiveness, says Dr Soheil Radfar, a hurricane-hazard modeller at Princeton University. Radfar, who is the lead author of the new study, tells Carbon Brief:
“Hurricane damage starts days before the landfall…Four or five days before a hurricane making landfall, we expect to have high wind speeds and, because of that high wind speed, we expect to have storm surges that impact coastal communities.”
They also find that rapidly intensifying storms have higher peak rainfall than non-rapidly intensifying storms, with marine heatwave-influenced, rapidly intensifying storms exhibiting the highest average rainfall at landfall.
The charts below show the mean sustained wind speed in knots (top) and the mean rainfall in millimetres per hour (bottom) for the tropical cyclones analysed in the study in the five days leading up to and two days following a storm making landfall.
The four lines show storms that: rapidly intensified with the influence of marine heatwaves (red); those that rapidly intensified without marine heatwaves (purple); those that experienced marine heatwaves, but did not rapidly intensify (orange); and those that neither rapidly intensified nor experienced a marine heatwave (blue).
Dr Daneeja Mawren, an ocean and climate consultant at the Mauritius-based Mascarene Environmental Consulting who was not involved in the study, tells Carbon Brief that the new study “helps clarify how marine heatwaves amplify storm characteristics”, such as stronger winds and heavier rainfall. She notes that this “has not been done on a global scale before”.
However, Mawren adds that other factors not considered in the analysis can “make a huge difference” in the rapid intensification of tropical cyclones, including subsurface marine heatwaves and eddies – circular, spinning ocean currents that can trap warm water.
Dr Jonathan Lin, an atmospheric scientist at Cornell University who was also not involved in the study, tells Carbon Brief that, while the intensification found by the study “makes physical sense”, it is inherently limited by the relatively small number of storms that occur. He adds:
“There’s not that many storms, to tease out the physical mechanisms and observational data. So being able to reproduce this kind of work in a physical model would be really important.”
Economic costs
Storm intensity is not the only factor that determines how destructive a given cyclone can be – the economic damages also depend strongly on the population density and the amount of infrastructure development where a storm hits. The study explains:
“A high storm surge in a sparsely populated area may cause less economic damage than a smaller surge in a densely populated, economically important region.”
To account for the differences in development, the researchers use a type of data called “built-up volume”, from the Global Human Settlement Layer. Built-up volume is a quantity derived from satellite data and other high-resolution imagery that combines measurements of building area and average building height in a given area. This can be used as a proxy for the level of development, the authors explain.
By comparing different cyclones that impacted areas with similar built-up volumes, the researchers can analyse how rapid intensification and marine heatwaves contribute to the overall economic damages of a storm.
They find that, even when controlling for levels of coastal development, storms that pass through a marine heatwave during their rapid intensification cause 93% higher economic damages than storms that do not.
They identify 71 marine heatwave-influenced storms that cause more than $1bn (inflation-adjusted across the dataset) in damages, compared to 45 storms that cause those levels of damage without the influence of marine heatwaves.
This quantification of the cyclones’ economic impact is one of the study’s most “important contributions”, says Mawren.
The authors also note that the continued development in coastal regions may increase the likelihood of tropical cyclone damages over time.
Towards forecasting
The study notes that the increased damages caused by marine heatwave-influenced tropical cyclones, along with the projected increases in marine heatwaves, means such storms “should be given greater consideration” in planning for future climate change.
For Radfar and Moftakhari, the new study emphasises the importance of understanding the interactions between extreme events, such as tropical cyclones and marine heatwaves.
Moftakhari notes that extreme events in the future are expected to become both more intense and more complex. This becomes a problem for climate resilience because “we basically design in the future based on what we’ve observed in the past”, he says. This may lead to underestimating potential hazards, he adds.
Mawren agrees, telling Carbon Brief that, in order to “fully capture the intensification potential”, future forecasts and risk assessments must account for marine heatwaves and other ocean phenomena, such as subsurface heat.
Lin adds that the actions needed to reduce storm damages “take on the order of decades to do right”. He tells Carbon Brief:
“All these [planning] decisions have to come by understanding the future uncertainty and so this research is a step forward in understanding how we can better refine our predictions of what might happen in the future.”
The post Marine heatwaves ‘nearly double’ the economic damage caused by tropical cyclones appeared first on Carbon Brief.
Marine heatwaves ‘nearly double’ the economic damage caused by tropical cyclones
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