We cannot negotiate with the melting point of ice.
The 2025 State of the Cryosphere Report reveals accelerating losses of ice sheets, mountain glaciers, sea ice and permafrost. This impacts everyone, but growing damage could still be reduced - barely.
The comprehensive report1, coordinated by the International Cryosphere Climate Initiative (ICCI), comes from over 50 leading cryosphere scientists and details accelerating melt from the world’s frozen ice since the signing of the Paris Agreement in 2015.
Three messages are clear. Things are bad, they will get much worse, but its not too late to make a meaningful difference.
The report is timed to coincide with the COP30 climate conference in Brazil as well as the Climate Leaders Action Summit and the simultaneous publication of new “Highest Possible Ambition” (HPA) pathways from the Potsdam Institute and Climate Analytics.2 These suggest that with maximum commitment, maximum temperatures can be kept below 2°C before lowering to 1.5°C by 2100. We have to start now though and there are a lot of caveats and potential issues with the model which I’ll discuss further down.
The report paints pictures of the differences we can expect if follow the current trajectory (+3°C or more) versus getting our collective acts together and following the HPA pathways.
Ice Sheets and Sea-level Rise
The vast ice sheets covering Greenland and Antarctica play a vital role in regulating Earth’s climate, global ocean circulation, and determining the pace and magnitude of sea-level rise.
The report confirms that the temperature threshold for the stability of the polar ice sheets in Greenland and Antarctica is just +1°C. We have therefore passed that threshold and indeed melt rates are accelerating. Greenland is losing ice 5 times faster and Antarctica 6 times faster then just 30 years ago, bringing them closer to crossing irreversible tipping point thresholds that will impact humanity for millennia.
While several meters of sea level rise from this melting alone is now inevitable, we can still influence the rate of rise, even to the point where feasible adaptation is possible around the globe. Both ice sheets have tipping point thresholds that could be passed by 2040 or 2050. The West Antarctic Ice Sheet is just 0.25°C of ocean warming away from collapse. Even holding today’s temperature for a century or more could still result in its demise.
New Paleoclimate evidence from the last interglacial, 125,000 years ago, show significantly higher Antarctic and Greenland melt than the recent Holocene when temperatures were +1.5°C but with much lower CO2 levels. Of even more concern, short term peaks of 3.5-4 meters of sea level rise a century have been detected due to the collapse of vulnerable ice-sheet sectors. Such extensive and rapid sea-level rise would be catastrophic for today’s coastal cities and communities – yet we are currently on track for even higher temperatures and greenhouse gas concentrations than those that drove this incredible rate, and we are approaching those temperatures at an unprecedented speed.
Improvements in scientific understanding and modelling suggest faster melting of both ice sheets than reported in the 2021 IPCC reports. Movement of water beneath Antarctic ice sheets increase ice discharge threefold compared to older models. Including processes of crevasse and rift formation doubles the projections of ice loss from Thwaites, the Doomsday Glacier.
Sea-level rise also drives salty water into coastal aquifers affecting the availability of freshwater for drinking and crop irrigation. This is already affecting areas such as Bangladesh and the eastern Mediterranean. New projections show this will cause 77% of the world’s coastlines to undergo measurable saltwater intrusion by 2100.
Mountain Glaciers and Snow
Glacier ice loss around the world is accelerating incredibly quickly. Between 2000 and 2023, glaciers outside of Antarctica and Greenland lost 273 billion tonnes of ice a year, the rate was 36% higher since 2012 showing the level of acceleration. Central Europe has lost almost 40% of its ice since 2000. Glaciers in Western Canada and conterminous United States have lost 12% of their mass and those in Switzerland 13% since 2020!
Snowpack has followed a similar trajectory, declining in both thickness and duration.
The future of glaciers and snow is linked to temperature rise. Scandinavia and western north America will lose virtually all their ice at 2°C but a 1.5°C trajectory could save 20% of it. Even the higher central and eastern parts of High Mountain Asia are projected to lose 60% of existing ice under a 1.5°C emissions scenario, with only 15% remaining at 3.0°C. The Hindu Kush and Karakoram regions, which in recent decades were near stable, stand to lose 40% of their ice mass under a 2°C future but only 15% under a 1.5°C pathway. The impacts of this loss include water, food, economic and political insecurity, and should be considered essentially permanent on human time scales.
This is the area where rapid action can have the fastest and greatest impact. Losses could be stabilised by 2060 under the highest ambition pathway. If current policy is allowed to persist, the acceleration will continue requiring continual recalculation of adaptation measures for food, water and energy security for billions of people around the world, as well as ecosystem impacts.
The report provides a breakdown of the world’s glacial regions together with the steady temperatures required to melt them by 50%. Virtually all areas lose half their volume by +2°C which is likely, under current policy, to be reached by 2040, just 15 years from now. The losses by 3°C are huge, with no areas retaining even a third of their 2020 levels.
A very low emissions pathway is therefore essential to preserve the ecosystem services glaciers provide, which are already facing losses and extinctions, and to minimise the risk of severe hazards such as glacial lake outburst floods that accompany loss of mountain glaciers. The need to cut emissions is underscored by recent research that confirms even high-altitude glaciers previously considered to be less hazard-prone are capable of producing catastrophic and cascading floods.
Snow cover is also diminishing rapidly which reduces the albedo of the surface allowing more solar radiation to warm the underlying soil and rock. Winter seasons are shrinking. Even in the high-latitude Arctic, spring snow melt has been occurring 1–2 weeks earlier over the past fifteen years. Water stored in the snow and snow-fed underground aquifers will decrease, as already reported in many mountain areas. Continued declines in annual snowpack will result in negative economic impacts for many sectors, especially agriculture, hydropower, and tourism and threaten the availability of sufficient water supplies for major downstream population centres, from Los Angeles and Bangladesh to Marrakech and Delhi.
The 2026 Winter Olympic organisers have already stated that 2.4 million cubic meters of artificial snow will be required for the event despite all the runs being over 1,200 meters above sea level. This will consume almost a million tonnes of water.3
Every fraction of a degree of global temperature rise substantially impacts the loss of the mountain cryosphere.
Polar Oceans
Polar oceans are vital in regulating Earth’s climate by absorbing heat and carbon, acting as engines for global ocean circulation and as a basic component of marine food webs.
These functions are threatened by CO2 accumulation, both indirectly through the warming effect but also directly through ocean acidification. Concentrations in the atmosphere exceeded 430 ppm for the first time in May 2025 since the Miocene 10 million years ago. Mean ocean acidification has reached levels extremely challenging and potentially lethal for shelled marine life in some polar ocean sectors, especially the Arctic Ocean which has seen an acidity increase of 40%.
A new assessment confirms that ocean acidification levels have breached their safe Planetary Boundary this year. As a result, there has been a loss of suitable habitat for keystone shell-building species by about 60% for polar pteropods and about 40% for coral reefs – both vital components of marine food webs . Escalating ocean acidification has also occurred in the high Atlantic of Northwest Europe, particularly the UK and Ireland. If current emissions continue, ocean acidification could also begin to damage shelled creatures in parts of the Northwest European Shelf seas, threatening the broader food web in this region, and by extension, local and regional economies.
Sea-ice is also declining with the Antarctic sea-ice falling rapidly since 2016, a point before which it had been relatively stable. 2025 saw the record lowest global sea-ice measurement. Shipping through the Arctic is increasing as the ice recedes increasing the risk of pollution, ecosystem disruption and accidents.
Melting glaciers, ice sheets, and increased Arctic river runoff are adding large volumes of freshwater to the polar oceans. This reduces the salinity of surface water, creating a cold, lower-density layer on top of the saltier, denser water below. This layering, or stratification, prevents the vertical mixing of nutrients, heat, and carbon through the ocean, with far-reaching implications for global marine ecosystems and the carbon cycle.
One of the most far-reaching climatic consequences of polar ocean freshening is the weakening of the Atlantic Meridional Overturning Circulation (AMOC). Multiple observations show a significant weakening of the AMOC over recent decades and virtually all climate models show a further decline and/or collapse within a century under current policy. AMOC decline and collapse will have far reaching implications for northern European climate, sea-level rise and global rainfall belt positioning. The UK would experience winters of -20°C but with hotter and dryer summers than today, something the infrastructure is simply not capable of dealing with. The temperature gradient between northern and southern Europe would drive incredible storms. The tropical rain belts would shift south leaving current food producing areas in drought and current arid areas flooded.
Personally I find this chart with the observed trend overlay terrifying and compelling evidence that major disruptive change is on its way. Rapid and deep decarbonisation is the only way to delay this inevitability.
The Antarctic Circumpolar Current (ACC) is also weakening and expected to reduce by 20% by 2050. The ACC is crucial for global heat and nutrient transport, for atmospheric carbon uptake, and for connecting ocean basins. Because the ACC is linked to the AMOC, a weakening of this current would reverberate through global ocean current systems for centuries . This trend appears largely driven by Antarctic Ice Sheet melt. Models now also predict a nearly 50% intensification of the Antarctic Slope Current (ASC) along the Antarctic continental shelf from 2025 to 2050 with high emissions. A strengthened ASC could trigger instabilities that allow warm eddies to further erode Antarctic ice shelves, accelerating ice loss and, in a potential feedback mechanism, weakening the ACC even further.
Reducing overturning in both the Arctic and Antarctic also reduces carbon sequestration since carbon rich surface waters that have absorbed some of our emissions are not sunk to the depths. Reduced sea ice on the other hand allows carbon rich deep water to reach the surface and ‘outgas’ CO2 collected from the seabed to the atmosphere.
Sea Ice
Sea ice may seem superficial as it comes and goes with the seasons, but it is essential for maintaining a livable planet. It affects weather and ocean currents, it helps regulate Greenland and Antarctic ice sheet melt rates, and provides habitats for ice dependent species at the base of the food chain.
Sea ice statistics have continued their worrying declining trend. At both poles coverage has declined between 40-60% since satellite observations started in 1979. Virtually all of the Antarctic losses have occurred since 2016. Losses are year round, not just in the minimums that attract the headlines. A record-low maximum extent occurred in the Arctic in March 2025, and Antarctica’s record-low maximum was set in September 2023. Global sea-ice coverage, combining both poles, reached a record all-time low in February 2025.
Sea ice has not only declined in extent but also in thickness. Much of the Arctic Ocean used to be covered in thick, multi-year ice that was 4–7 years old. Such “old” ice has virtually disappeared, with even two or three-year- old ice comprising under 10% of today’s sea-ice coverage. Thinner ice is more susceptible to further breakup by storms.
A critical aspect of sea ice happens when it is created. The ice is formed out of sea water, but the ice itself consists of freshwater. The salt is expelled as the ice forms, creating cold dense high-salinity brine that sinks to the bottom of the ocean. This “bottom water” formation drives the main ocean currents. The observed 40% decline in sea ice in the Weddell Sea has reduced the production of Antarctic Bottom Water in this region by almost a third.
Massive disruptions in krill and phytoplankton populations appear to have occurred in the Southern Ocean due to the rapid decline of Antarctic sea ice since 2016 . This shift could decrease the dominance of the krill-centric food web, with severe impacts on Southern Ocean species . It could also lessen the biological transport of carbon into the deep ocean, with implications for the global ocean carbon sink, in which the Southern Ocean currently absorbs more carbon than any other ocean region.
Sea ice loss is also a feedback mechanism that increases warming. Ice is highly reflective, up to 90% compared to blue ocean which is less than 20%. This affects the Earth’s energy imbalance by reflecting less and absorbing more of the Sun’s short wave radiation. Added to cloud area and brightness declines, this increase in absorbed radiation is accelerating global warming, which in turn melts more ice in a feedback loop. This also drives a phenomena called Arctic Amplification which is seeing the region warm 3-4 times faster than the global average, further driving increased ice melt on land.
We can expect at least one ice-free Arctic summer within the next couple of decades. If highest possible ambitions are realised, some reversal may even be possible by the end of the century. AMOC slowdown may assist in the Arctic winter ice formation, but obviously comes with other terrible consequences.
Permafrost
Permafrost is ground that remains frozen for at least two years. It consists of a mixture of soil, rocks, sand, and organic matter bound together by ice, extending from one meter to over a thousand meters deep. Permafrost contains vast amounts of ancient organic carbon stored in the form of plant, animal, and microbe remains that have accumulated over thousands of years. This carbon is locked in the ground until it thaws.
Its thawing!
Permafrost underlays 22% of the land area in the Northern Hemisphere. It is also present in Antarctica as well as the South American Andes and New Zealand’s Southern Alps. Permafrost also occurs in shallow Arctic Ocean regions flooded after the last Ice Age.
Permafrost regions are warming rapidly through Arctic Amplification which makes them especially vulnerable and responsive to every fraction of a degree of global warming. As it thaws, microbes begin decomposing the organic matter releasing carbon dioxide and methane. This process continues for centuries and is unstoppable once initiated.
Permafrost emissions are now being quantified and it has been confirmed that the Arctic is now a net source of CO2 rather than a sink. More CO2 is being released through melting permafrost than is being absorbed by increased plant growth in the region. This is in spite of the lengthening growing season, warmer climate and carbon dioxide fertilisation effect.
The annual emissions are meaningful. Currently they equate to the same emissions as Japan (a top 10 emission country) and will soon match India as 1.5°C is breached. At 2°C annual permafrost emissions will be equal to the whole 38 country OECD European region. Exceeding 3°C will see emissions equal the US or China.
Once started, these emissions are unstoppable, meaning they would have to be matched by negative emissions (carbon capture) in order to maintain global net-zero and bring any stability to the climate. This inevitability is not included in any country’s NDCs, wiring in failure of achieving the Paris goals.
Thoughts and Conclusions
COP events drive the regular climate reporting season. This year the main outputs such as the 2025 State of the Climate Report4, The Planetary Boundaries update5, the Tipping Point Report6 and the Production Gap Report7 all contain bad news of a crisis in full development with little time to react. The State of the Cryosphere report is different though. It stands out because its reporting that we have already passed a critical threshold. The threshold to save the cryosphere was 1°C of warming, so now we are approaching 1.5°C, every system is in deep trouble, driving irreversible change, engaging feedbacks and accelerating.
The two stand out systems from this year’s report for me are the state of the AMOC and the Permafrost predicament.
The chart further above that overlays observed AMOC weakening on the model predictions did shock me. It shows that the point of no return is close. It also helps explain Prof. Tim Lenton’s statement at the recent Global Heating Emergency Conference8, that there is a 10% chance that the AMOC has already passed its tipping point. The ramifications of this are profound and will redefine the entire European climate in the long term, but bring increasingly volatile and dangerous extremes in the coming decades.
The Permafrost situation is alarming as it now bakes in continuous and increasing natural emissions for centuries to come. The higher we allow temperatures to get, the worse it becomes and the more difficult it will be for future generations to lower greenhouse gas concentrations, let alone keep up with increasing natural emissions. Recent research has shown how permafrost melt drove the deglaciation at the end of the last ice age9 and now has the potential to catapult the Earth into a hot house regime.
That’s not to take anything away from the other systems that are covered in the report. Glacial loss is astounding and will have far reaching consequences. Sea ice loss is starting to affect the ocean’s carbon sink capacity, currents and albedo, all of which are feedbacks for faster warming. The ice sheets are melting faster than predicted with new models suggesting further acceleration driving more rapid sea level rise.
The report’s authors do their best to remain positive by showing how the Highest Possible Ambition scenario can reduce the damage, or at least the rate of escalating damage. When compared to the growing weight of climate science evidence of accelerating warming, the increasing Earth Energy Imbalance, the loss of global albedo and the fact that the natural system as a whole is losing its ability to sink our carbon emissions, these hopes look unachievable, even if they were remotely politically possible. The HPA approach discounts all of these and runs on a, now known to be, out of date and far too reticent a temperature model.
Limiting global warming to 1.5°C is no longer possible. There is a strong probability that 2°C will be passed in the late 2030s and 3°C is certainly possible by 2060, even 2050.
The world must now prepare for higher temperatures and a longer period of overshoot before temperatures can be lowered again, if indeed they can be on any meaningful human scale. Tragically, this will result in greater cryosphere loss and downstream impacts, with greater sea-level rise, water supply losses and polar ocean acidification damages locked in for hundreds to thousands of years.
The report does present a balance between what will happen if we continue to do virtually nothing to reduce our still growing emissions and if were to actually try though. Every fraction of a degree does indeed matter which means every tonne of reduced or avoided emissions makes a difference. We still have some say in the matter.
ICCI, 2025. State of the Cryosphere 2025: Ice Loss = Global Damage. International Cryosphere Climate Initiative (ICCI), Stockholm, Sweden. 52 pp.
Highest Possible Ambition Report. https://climateanalytics.org/publications/rescuing-1-5c
William J Ripple, Christopher Wolf, Michael E Mann, Johan Rockström, Jillian W Gregg, Chi Xu, Nico Wunderling, Sarah E Perkins-Kirkpatrick, Roberto Schaeffer, Wendy J Broadgate, Thomas M Newsome, Emily Shuckburgh, Peter H Gleick, The 2025 state of the climate report: a planet on the brink, BioScience, 2025;, biaf149, https://doi.org/10.1093/biosci/biaf149
2025 Planetary Health Check - https://www.planetaryhealthcheck.org
Global Tipping Points 2025 - https://global-tipping-points.org
2025 Production Gap Report - https://productiongap.org/2025report/
Amelie Lindgren et al., Massive losses and gains of northern land carbon stocks since the Last Glacial Maximum.Sci. Adv.11,eadt6231(2025).DOI:10.1126/sciadv.adt6231
Thank you Tom, another beautifully presented analysis. Here's my prediction FWIW: business as usual until economic collapse, then a global last gasp push into geoengineering, but by then the Titanic will be inexorably crashing into the last iceberg still refusing to melt away. I'm nearly 60 and I now would prefer my kids not to have kids. Heartbreaking really.
And living in the UK it's the AMOC collapse that keeps me up at night