Greenland is closing in on three decades of continuous annual ice loss, with 1995-96 being the last year in which the giant ice sheet grew in size.
With another melt season over, Greenland lost 105bn tonnes of ice in 2024-25.
The past year has seen some notable events, including ongoing ice melt into the month of September – well beyond the end of August when Greenland’s short summer typically draws to a close.
In a hypothetical world not impacted by human-caused climate change, ice melt in Greenland would rarely occur in September – and, if it did, it would generally be confined to the south.
In this article, we explore how Greenland’s ice sheets fared over the 12 months to August 2025, including the evidence that the territory’s summer melting season is lengthening.
(For our previous analyses of Greenland’s ice cover, see coverage in 2024, 2023, 2022, 2021, 2020, 2019, 2018, 2017, 2016 and 2015.)
Surface mass balance
The seasons in Greenland are overwhelmingly dominated by winter.
The bitterly cold, dark winter lasts up to ten months, depending on where you are. In contrast, the summer period is generally rather short, starting in late May in southern Greenland and in June in the north, before ending in late August.
Greenland’s annual ice cycle is typically measured from 1 September through to the end of August.
This is because the ice sheet largely gains snow on the surface from September, accumulating ice through autumn, winter and into spring.
Then, as temperatures increase, the ice sheet begins to lose more ice through surface melt than it gains from snowfall, generally from mid-June. The melt season usually continues until the middle or end of August.
Over this 12-month period, scientists track the “surface mass balance” (SMB) of the ice sheet. This is the balance between ice gains and losses at the surface.
To calculate ice gain and losses, scientists use data collected by high-resolution regional climate models and Sentinel satellites.
The SMB does not consider all ice losses from Greenland – we will come to that later – but instead provides a gauge of changes at the surface of the ice sheet.
According to our calculations, Greenland ended the year 2024-25 with an overall SMB of about 404bn tonnes. This is the 15th highest SMB in a dataset that goes back 45 years, exceeding the 1981-2010 average by roughly 70bn tonnes.
This year’s SMB is illustrated in the maps and charts below, based on data from the Polar Portal.
The blue line in the upper chart shows the day-to-day SMB. Large snowfall events become visible as “spikes”. The blue line in the lower chart depicts the accumulated SMB since 1 September 2024. In grey, the long-term average and its variability are shown. For comparison, the red line shows the record-low year of 2011-12.
The map shows the geographic spread of SMB gains (blue) and losses (red) for 2024-25, compared to the long-term average.
It illustrates that southern and north-western Greenland had a relatively wet year compared to the long-term average, while there was mass loss along large sections of the coast, in particular in the south-west. The spikes of snow and melt are clearly visible in the graphs on the right.
Lengthening summer
Scientists have traditionally pinned the start of the “mass balance year” in Greenland to 1 September, given that this is when the ice sheet typically starts to gain mass.
However, evidence has started to emerge of a lengthening of the summer season in Greenland – as predicted some time ago by climate models.
The start of the 2024-25 mass balance year in Greenland saw ice melt continuing into September. This included a particularly unusual spike in ice melt in the northern part of the territory in September as well as all down the west coast.
In a world without human-caused climate change, ice melt in September would be very rare – and generally confined to the south.
Greenland also saw an early start to the summer melt season in 2025. The onset of the melting season, defined as the first of at least three days in a row with melting over more than 5% of the ice sheet, was on 14 May. This is 12 days earlier than the 1981-2025 average.
The maps below show the extent of melt (red shading) across the ice sheet on 24 September 2024 (left) and 20 May 2025 (right). The blue lines in charts beneath show the percentage melt in 2024 (left) and 2025 (right), up to these dates, compared to the 1981-2010 average (grey).
The melt season began with a significant spike of melting across the southern part of the ice sheet. This happened in combination with sea ice breaking up particularly early in north-west Greenland, allowing the traditional narwhal hunt to start much earlier than usual.
Surface melt
The ablation season, which covers the period in the year when Greenland is losing ice, started a little late. The onset of the season – defined as the first of at least three days in a row with an SMB below -1bn tonnes – began on 15 June, which is two days later than the 1981-2010 average.
Overall, during the 2025 summer, a remarkably large percentage of the ice sheet was melting at once. This area was larger than the 1981-2010 average for three and a half months (mid-June to end of September).
In mid-July, melting occurred over a record area. For three days in a row, melting was present over more than 80% of the area of the ice sheet – peaking at 81.2%. This is the highest value in our dataset, which started in 1981.
The red shading in the maps below shows the extent of melting across Greenland on 19 July (left) and 30 September (right) 2025. The charts beneath show the daily extent of melting through 2025 (blue line), up to these dates, compared to the 1981-2010 average.
Snowfall
However, the SMB is not just about ice melt.
There was a lack of snowfall in the early winter months (September to January), particularly in south-east Greenland, which is typically the wettest part of the territory. The months that followed then saw abundant snow, which brought snowfall totals up closer to average by the start of summer.
A cold period at the end of May and in June protected the ice sheet from excessive ice loss. Melt then continued rather weakly until mid-July.
This was followed by strong melting rates in the second half of July and again in mid-August.
Overall, with both ice melt and snowfall exceeding their historical averages for the year as a whole, the SMB of the Greenland ice sheet ended above the 1981-2010 average.
These increases in snowfall and melt are in line with what scientists expect in a warming climate. This is because air holds more water vapour as it warms – leading to more snowfall and rain. Warmer temperatures also lead to more ice melt.
Total mass balance
The surface mass balance is just one component of the “total” mass balance (TMB) of the Greenland ice sheet.
The total mass balance of Greenland is the sum of the SMB, the marine mass balance (MMB) and basal mass balance (BMB). In other words, it brings together calculations from the surface, sides and base of the ice sheet.
The MMB measures the impact of the breaking off – or “calving” – of icebergs, as well as the melting of the front of glaciers where they meet the warm sea water. The MMB is always negative and has increased towards more negative values over the last decades.
BMB refers to ice losses from the base of the ice sheet. This makes a small negative contribution to the TMB.
(The only way for the ice sheet to gain mass is through snowfall.)
The continued mass loss observed in Greenland is primarily due to a weakening of the SMB – caused by rising melt combined with insufficient compensation of lost ice through snowfall.
The figure below shows how much ice the Greenland ice sheet has lost (red) going back to 1987, which includes the SMB (dark blue), MMB (mid blue) and BMB (light blue). The analysis, which uses data from three models, is based on 2021 research published in Earth System Science.
Despite a relatively high SMB, high calving rates meant that Greenland lost 105bn tonnes of ice over the 12-month period.
This means that 2024-25 was the 29th year in a row with a Greenland ice sheet overall mass loss. As the chart shows, Greenland last saw an annual net gain of ice in 1996.
Satellite data
The mass balance of the Greenland ice sheet can also be measured by looking at the Earth’s gravitational field, using data captured by the Grace and Grace-FO satellite missions – a joint initiative from NASA and the German Aerospace Center.
The Grace satellites are twin satellites that follow each other closely at a distance of about 220km, which is why they are nicknamed “Tom and Jerry”. The distance between the two depends on gravity – which is, in turn, related to changes in mass on Earth, including ice loss.
Therefore, the distance between the two satellites, which can be measured very precisely, can be used to calculate loss of mass from the Greenland ice sheet.
Overall, the satellite data reveals that Greenland’s ice sheet lost around 55bn tonnes of ice over the 2024-25 season.
There is reasonably good agreement between the Grace satellite data and the model data, which, as noted above, finds that 105bn tonnes of ice was lost in Greenland over the same period.
However, the alignment of the two datasets – which are fully independent of each other – becomes more clear once a longer time period is considered.
In the 22-year period between April 2002 and May 2024, the Grace data shows that Greenland lost 4,911bn tonnes of ice. The modelling approach, on the other hand, calculates that 4,766bn tonnes of ice was lost.
The figure below shows gain and loss in the total mass of ice of the Greenland ice sheet, calculated using Grace satellite measurements. It reveals that, over the past 23 years, there has been mass loss in the order of several metres along the coasts of Greenland, with the most significant losses seen on the western coast. Over the central parts of the ice sheet, there has been a small mass gain.
The lower figure shows the contribution of Greenland mass change to sea level rise over the last 23 years, according to the satellite data. It illustrates that more than 5,000bn tonnes of ice have been lost over the time period – contributing to roughly 1.5cm of sea level rise.
Warm over Europe and North America, cool over Greenland
As always, the weather systems across the northern hemisphere play a key role in the melt and snowfall that Greenland sees each year.
As in previous years, multiple heatwaves were observed in southern Europe and North America over the summer of 2025.
And, just like in 2024, there was only modest heat in northern Europe – with the notable exception of Arctic Scandinavia – with a comparably cool and rainy July followed by a warmer and sunnier August.
The high-pressure weather systems that bring heatwaves have a wide-ranging impact on weather extremes across the northern hemisphere.
Strong blocking patterns over North America and Europe were repeatedly present in the course of the summer of 2025. In such a blocked flow, the jet stream – fast-moving winds that blow from west to east high in the atmosphere – is shaped like the Greek capital letter Omega (Ω).
The jet stream bulged up to the north over Canada and northern Europe. West and east of these ridges, low pressure troughs were found at both “feet” of the Omega. One of these troughs was located over Greenland (top left panel in next figure).
This resulted in widespread heat near the cores of these high-pressure systems, fuelling fires in several countries, including large wildfires in Canada. Smoke from these wildfires reached Greenland and Europe in late May.
Unlike in previous years, no heavy precipitation events were observed near the “feet” of the Omega.
If the Omega pattern is displaced by half a wavelength, the opposite – warm over Greenland, with cool continents – is also possible.
This circulation pattern occurred in August 2025 and is shown in the top right panel of the figure below. The bottom panel depicts the large temperature variability in May 2025.
The post Guest post: How the Greenland ice sheet fared in 2025 appeared first on Carbon Brief.
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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