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At Cop26 in Glasgow hundreds of governments and private institutions joined together in a series of pledges promising ambitious goals on methane reduction, forest protection and the shift of finance away from fossil fuels.

Nearly two years on, Climate Home News looks at how these commitments are holding up to the test of time.

METHANE PLEDGE

WHAT: Reduce human-made methane emissions by 30% between 2020 and 2030. Cutting the amount of methane present in the atmosphere is important because it is a much more powerful greenhouse gas than carbon dioxide despite having a shorter lifespan.

WHO: 104 countries, led by the US and the EU, signed up to the pledge when it was first announced at Cop26 in Glasgow. The number of signatories has since risen to 150. However, they only represent about half of global methane emissions as China, India and Russia – three of the world’s top four emitters – have not joined the coalition.

HOW IT IS GOING: The raw figures paint a fairly grim picture. Since Cop26, the concentration of methane in the atmosphere has kept rising fast and it is now more than two and a half times its pre-industrial level.

Over half of the emissions come from human activities, like fossil fuel extraction, farming and landfills, with the rest caused by natural sources. Under current trajectories, total human-made methane emissions could rise by up to 13% between 2020 and 2030 – the pledge’s timeframe.

This graph shows the globally-averaged, monthly atmospheric methane concentration since 1983. Image credit: NOAA Global Monitoring Laboratory

Targeting the oil and gas sector is seen by many as the easiest and fastest way to bring down emissions in the near term. Experts say existing technologies already provide cheap and effective ways to plug leaky infrastructure like pipelines and gas storage tanks.

However, the technological developments have not yet been converted into real, widespread action. According to the International Energy Agency (IEA), methane emissions from oil and gas remained “stubbornly high” in 2022 even as the energy companies’ bumper profits made actions to reduce them cheaper than ever. “There is just no excuse”, the IEA chief Fatih Birol commented.

Raft of initiatives

But judging the pledge’s progress on current numbers only tells half the story, argued Jonathan Banks, global director of the methane programme at the Clean Air Task Force (CATF). “Emissions are not going to turn around immediately,” he told Climate Home. “If you look at the work going into the pledge, building the funding and technical resources to bring emissions down, I think it could potentially be on track for success”.

A series of initiatives have been set up to help countries deliver on the pledge. The UN’s Climate and Clean Air Coalition (CCAC) is helping over 30 developed and developing countries to establish plans to achieve the 2030 target.

Canada has set out a strategy that it expects to reduce domestic methane emissions by “more than 35%” by 2030, compared to 2020.

Methane leaking from Chelmsford compressor station, UK on 15 October 2021, picked up by a special camera (Photo: Clean Air Task Force/ James Turitto)

The Global Methane Hub (GMH), a philanthropic organisation, is also supporting signatories of the methane pledge with technical assistance and funding. Carolina Urmeneta, a director at the GMH, told Climate Home News that over the last year, the group has focused its work on developing systems to monitor methane emissions rates from oil and gas and landfill installations using satellites.

She said reaching the 2030 target “is possible and cost-effective, but it is not easy. We need to improve data transparency and increase funding for projects with methane targets.”

Regulations drive

Some progress has also been made on the regulatory front. The USA introduced new rules to address methane emissions caused by oil and gas companies through the Inflation Reduction Act. Using a carrot-and-stick approach, it provides $1 billion in public subsidies to take action, while charging a fee for excessive emissions.

In May the European Parliament agreed on tougher measures to tackle methane emissions in the energy sector. The approved text calls for binding emission reduction targets, stronger obligations for fossil fuel operators to detect and repair leaky infrastructure and the application of the same measures to exporting countries outside of the bloc.

While the final rules are still being negotiated with the EU’s national governments, CATF’s Banks believes they could have a “huge global impact” if introduced in their current form. “The methane emissions associated with the gas Europe buys from the rest of the world is quite large, so such measures could really drive some change”.

New announcements are expected at Cop28 in Dubai, after the summit’s president Sultan Al Jaber set the phaseout of methane emissions in oil and gas by 2030 as one of his priorities. “More than 20 oil and gas companies have answered Cop28’s call,” he said this week. “And I see positive momentum as more are joining”. But the UAE has been accused of double standards as it failed to report methane emissions to the UN for a decade, as the Guardian reported.

While it has not signed the pledge, China is expected to announce its long-awaited methane plan at Cop28.

FOREST PLEDGE 

WHAT: End and reverse deforestation by 2030. Country leaders pledged to conserve forests, tackle wildfires, facilitate sustainable agriculture, support indigenous populations and “significantly” increase the provision of finance towards achieving those goals.

WHO: More than 140 countries joined the coalition. Signatories of the pledge – including large forest nations like Brazil, Indonesia and the Democratic Republic of Congo – cover around 90% of the world’s forests. But major G20 powers such as India, South Africa, Saudi Arabia and rainforest nations like Bolivia and Venezuela did not join the group.

HOW IT IS GOING:  Countries remain off track to reach the goal of the Glasgow pledge and end deforestation by 2030, according to an assessment done by a coalition of NGOs.

Across the world, tree loss recorded in 2022 was 21% higher than the level needed to be on course to reach zero in seven years’ time, the report said.

Source: Forest Declaration Assessment

In fact, the situation is getting worse. Global deforestation grew 4% last year, wiping out 6.6 million hectares of forest, according to the study. That’s a tree-covered area nearly as big as Ireland disappearing in one year.

“The world’s forests are in crisis. All these promises have been made to halt deforestation, to fund forest protection. But the opportunity to make progress is passing us by year after year,” said Erin Matson, a lead author of the Forest Declaration Assessment.

Saving the Three Basins means stopping fossil fuel expansion

There are important regional differences, however. While tropical Asia is faring better, with Indonesia and Malaysia on track to hit their targets, Latin America and the Caribbean are farthest off track.

The election of President Lula da Silva in Brazil has led to a reversal in the skyrocketing deforestation rates in the country, which hosts most of the Amazon rainforets.

But efforts to create a regional forest protection coalition have failed. At the Amazon summit in August, eight South American countries failed to agree on a pledge to end deforestation by 2030 following opposition from Bolivia and Venezuela.

Cop26 pledges: Where are we on the forest, methane and finance commitments now?

An aerial view shows deforestation near a forest on the border between Amazonia and Cerrado in Nova Xavantina, Mato Grosso state, Brazil in 2021 (REUTERS/Amanda Perobelli)

While it included a larger number of countries, the Cop26 commitment was not entirely new: it repeated promises previously made in the 2014 New York Declaration on Forests, which by then had already failed to achieve some of its core targets.

Keen to avoid the same fate, self-declared “high ambition” countries launched a new initiative designed to deliver the pledge.

“High ambition” efforts

Chaired by the USA and Ghana, the Forest and Climate Leaders’ Partnership (FCLP) has promised to spur global action and provide accountability.

Only a fifth of the original 140 signatories have joined the group so far, with Russia and Indonesia among the most notable absentees.

Christine Dragisic, who leads the forest team at the US State Department, said the goal is to create a “high-level community” that brings together governments, indigenous people, philanthropies, civil society and the private sector to drive action forward and hit the 2030 target.

“Can we do it? Yes. Is it going to be hard? Definitely. Does it require everybody to be at the table? For sure”, Dragisic told Climate Home.

Cop26 pledges: Where are we on the forest, methane and finance commitments now?

An Indonesian ranger patrols a forest protected through a carbon credit project. Photo: Dita Alangkara/CIFOR

Since its launch last year, the FCLP has worked on a number of initiatives offering technical and financial solutions to forest nations, looking at the role of carbon markets and the forest economy in averting tree loss.

Finance gaps

As with most climate actions, however, it ultimately comes down to the question of money. “The delivery of climate finance is very important to achieve a lot of these targets and that is still very much lacking”, Roselyn Fosuah Adjei, director of climate change at Ghana’s forestry commission and co-chair of the FCLP, told Climate Home.

“The kind of finance we need is not finance for today or tomorrow, it’s finance for yesterday. We are already behind schedule. If it gets delivered fast there’s lots that we can do to close the gap that is now quite wide,” she added.

The Cop26 pledge was accompanied by a commitment from a group of rich nations to provide $12 billion in forest-related climate finance between 2021 and 2025. The money should be channeled to developing countries enacting concrete steps to halt forest loss.

The donor countries reported last year that they had provided $2.6 billion – over a fifth of the target amount – in 2021. They are expected to provide an update at Cop28.

INTERNATIONAL FOSSIL FINANCE PLEDGE

WHAT: End new direct public support for the international unabated fossil fuel energy sector by the end of 2022, except in limited and clearly defined circumstances that are consistent with a 1.5°C warming limit and the goals of the Paris Agreement.

WHO: 34 countries and five development banks – predominantly from wealthy cuontries – signed up to the pledge at Cop26. These included the G7 nations – with the exception of Japan – and most EU member states.

HOW IT IS GOING: Among the signatories that give lots of money to the energy sector, the vast majority have introduced policies in line with the promise made in Glasgow.

The United Kingdom, France, Denmark, New Zealand, Canada, Finland and Sweden have stopped providing loans and guarantees for oil and gas extraction and processing overseas through their export credit agencies.

Their actions have shifted at least $5.7 billion per year in public finance out of fossil fuels and into clean energy, according to analysis by Oil Change International and E3G.

On the other hand, however, the USA, Italy and Germany have continued funding international fossil fuel projects in 2023 in breach of the pledge.

They were supposed to stop funding foreign fossil fuels by December 2022. But since then, they collectively approved over $3 billion in financial support to oil and gas overseas programmes.

Most of the funding comes in the form of state-backed guarantees provided by export credit agencies. These products limit the risk taken by companies selling services and goods in other countries, influencing investment.

Among the projects receiving backing from the US and Italy was the expansion of an oil refining facility in Indonesia’s Borneo.

The US Export-Import Bank justified its backing of the project by claiming it would allow Indonesia to reduce its reliance on imported fossil fuels. The Italian agency did not provide a motivation for the decision.

Germany and the US have also poured hundreds of millions of dollars into projects aiming to boost the production and trade of liquified natural gas (LNG), which has been more sought after since Russia invaded Ukraine and Europe cut back on Russian gas.

Political splits and carve-outs

In the US, efforts to comply with the Glasgow pledge have caused a split among senior officials in the Biden administration and in the federal agencies charged with disbursing the money, as Politico revealed.

The White House has drafted guidance underpinning the investments - without making it public -, but the final decisions are made by agencies like the US Export-Import Bank (Exim).

“It is a struggle to get US Exim to comply, so far they’ve ignored the Cop26 commitment”, says Nina Pusic from Oil Change International. “It will require a lot of political weight from the Biden administration and Congress.”

Indonesia delays coal closure plans after finance row with rich nations

Italy looks likely to keep funding fossil fuels overseas for years to come. Its policy guidance lays out a "gradual dismission of public support to new requests of fossil fuel projects", seeing support for gas extraction and production run into 2026. Oil processing and distribution projects should be excluded from the beginning of next year.

But Italy has also carved out a wide range of exceptions that allow its export credit agency to keep greenlighting support for fossil fuel projects on "national energy security" and "energy efficiency" grounds.

FSRU Toscana LNG terminal. Cop26 pledges: Where are we on the forest, methane and finance commitments now?

The FSRU Toscana LNG regasfication platform off the coast of Italy (Photo: OLT Offshore LNG Toscana)

Germany's main export credit agency has just introduced this month new policies restricting support for fossil fuel projects. However, it allows for financing the development of new gas fields and related transport facilities until 2025 when justified by "national security and in compliance with the Paris Agreement targets".

Investment in new coal, oil and gas production is regarded as incompatible with limiting global warming to 1.5C, according to the International Energy Agency (IEA) and a large number of climate scientists.

"Germany has a vast amount of fossil fuel transactions pending approval", says Oil Change International's Pusic. "The success of the new policy will be judged on the decisions made on those projects".

GLASGOW FINANCIAL ALLIANCE FOR NET ZERO (GFANZ)

WHAT: Commit to achieving net zero emissions by 2050 at the latest by aligning their portfolios and investment practices with the goals of the Paris Agreement.

WHO: Over 650 institutions across the financial sector, including banks, insurers, asset owners, asset managers, financial service providers, and investment consultants. Gfanz members represent 40% of global private financial assets. They are grouped together under eight independent net-zero financial alliances focused on specific branches of finance.

HOW IT IS GOING: It is not easy to gauge the progress of a wide-ranging initiative with loosely defined targets and a constellation of constituent parts.

Above all, the mere fact that the alliance still exists at all is a first - albeit limited - marker of success, after an especially tumultuous year.

The prospect of ending up in legal hot waters in the US, where Republicans have driven an anti-climate investment backlash, has dampened the enthusiasm of many leading signatories. The result is that parts of the alliance have been hemorrhaging members, while other components have resorted to watering down their requirements to assuage concerns.

Cop26 pledges: Where are we on the forest, methane and finance commitments now?

Mark Carney, former Bank of England governor, launched GFANZ at Cop26. Photo: World Economic Forum/Valeriano Di Domenico

Troubles started brewing in mid-2022 when a group of leading US banks threatened to pull out over fears of being sued because of having decarbonisation policies imposed by external parties. That's after US Republican politicians had accused financial institutions of breaching antitrust rules by grouping together in a climate cartel that limits opportunities for investors.

A month later, in October 2022, Gfanz dropped a key requirement for its members to sign up to the UN Race to Zero initiative - a verification body for corporate and financial sector pledges - which had been seen as a way to prevent greenwashing.

Heading for the door

Those US banks eventually ended up staying in but, despite the less stringent criteria, other influential members began heading for the door in droves soon after.

Vanguard, one of the world's biggest asset managers, quit the Net Zero Asset Managers' initiative - part of Gfanz - saying it wanted to "provide clarity to investors" and "speak independently on matters of importance" to them.

But it's the insurers' coalition, known as NZIA, that has suffered the biggest - nearly fatal - wounds. The group has lost nearly two-thirds of its members since the start of the year, with leading firms like Allianz, Zurich, Munich Re and Lloyd's of London throwing in the towel.

Again a major driver for the mass exit was a letter written in May by 23 Republican attorney generals accusing signatories of advancing "an activists climate agenda" with "serious detrimental effects on the residents" of their states. The spark for this was the alliance's initial obligation to its members to set emission reduction targets by the end of July.

Staring at the real prospect of shutting down, the insurers' alliance again watered down its requirements, becoming effectively toothless.

To triple renewable energy, the Global South needs finance

"NZIA member companies have no obligation to set or publish targets", wrote the UN Environment Programme (Unep) - convener of the initiative -  in a clarification letter. "Each company who chooses to be a member of the NZIA unilaterally and independently decides on the steps on its path towards net zero."

Meanwhile, GFANZ says its members have submitted over 300 interim targets "representing clear progress in implementing commitments" to divert finance in line with net zero goals.

But while plans have been announced, many GFANZ members are also being accused of not putting their money where their mouth is. 161 members of the coalition have collectively invested hundreds of billions of dollars into the expansion of the coal, oil and gas industries since they joined the group, according to research by campaigning group Reclaim Finance.

The post Forests, methane, finance: Where are the Cop26 pledges now? appeared first on Climate Home News.

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What Is the Economic Impact of Data Centers? It’s a Secret.

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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.

What Is the Economic Impact of Data Centers? It’s a Secret.

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GEF raises $3.9bn ahead of funding deadline, $1bn below previous budget

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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”.

    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.

    Santa Marta conference: fossil fuel transition in an unstable world

    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.

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    Marine heatwaves ‘nearly double’ the economic damage caused by tropical cyclones

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    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).

    Average maximum sustained wind speed (top) and rate of rainfall (bottom) for tropical cyclones in the period leading up to and following landfall. Storms are categorised as: rapidly intensifying with marine heatwaves (red); rapidly intensifying without marine heatwaves (purple); not rapidly intensifying with marine heatwaves (orange); and not rapidly intensifying, without marine heatwaves (blue). Source: Radfar et al. (2026)
    Average maximum sustained wind speed (top) and rate of rainfall (bottom) for tropical cyclones in the period leading up to and following landfall. Storms are categorised as: rapidly intensifying with marine heatwaves (red); rapidly intensifying without marine heatwaves (purple); not rapidly intensifying with marine heatwaves (orange); and not rapidly intensifying, without marine heatwaves (blue). Source: Radfar et al. (2026)

    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.

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