A new landmark review delivers a stark message: the global warming target of +1.5°C is insufficient to protect the vast ice sheets of Greenland and Antarctica from catastrophic melting, potentially leading to several metres of sea-level rise in the coming centuries. The international team of scientists argues that even today’s warming of +1.2°C, if sustained, is already locking in dangerous levels of sea-level rise.
The Paris Agreement’s ambition to limit global warming to “well below +2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to +1.5°C” has been a cornerstone of global climate policy. However, this new synthesis of evidence from past warm periods, recent observations, and numerical modelling suggests this widely accepted threshold is far too high for the planet’s polar ice giants.
Lead author Professor Chris R. Stokes from Durham University, UK, stated in a Durham University press release about the study: “There is a growing body of evidence that 1.5 °C is too high for the ice sheets in Greenland and Antarctica. We’ve known for a long time that some sea level rise is inevitable over the next few decades to centuries, but recent observations of ice sheet loss are alarming, even under current climate conditions.”
Lessons from Earth’s Past Paint a Grim Picture
The researchers delved into Earth’s climate history, examining periods when global temperatures were similar to or slightly warmer than today. During the Last Interglacial (~125,000 years ago), when temperatures were just +0.5 to +1.5°C higher than pre-industrial levels, global mean sea level was likely 6 to 9 metres higher than present. Further back, during the Mid-Pliocene Warm Period (~3 million years ago), with CO2 concentrations similar to today (~350-450 ppm) and temperatures +2 to +5°C warmer, sea levels soared by 10 to 20 metres, implying an ice-free Greenland and a substantially smaller Antarctic ice sheet. These palaeorecords strongly indicate that even sustained warming at or just above 1°C commits the planet to multi-metre sea-level rise.
Today’s Ice Loss: An Accelerating Crisis
The past three decades have witnessed a quadrupling of mass loss from the Greenland and Antarctic ice sheets. These are no longer slumbering giants but are now the dominant contributors to global sea-level rise from the cryosphere. The Greenland Ice Sheet is particularly vulnerable, with the Arctic warming nearly four times faster than the global average. Its current rate of mass loss is unprecedented in at least the last 180 years.
In Antarctica, the West Antarctic Ice Sheet (WAIS) has seen accelerating ice discharge, especially from the Amundsen Sea Embayment, driven by the intrusion of warm ocean waters. Scientists warn that this region may have already tipped into a state of Marine Ice Sheet Instability (MISI), a self-reinforcing feedback where retreat into deeper bedrock accelerates ice flow. Worryingly, signs of mass loss are also emerging from marine-based sectors of the much larger East Antarctic Ice Sheet.
Models Confirm: No Respite at 1.5°C
Numerical ice sheet models, looking into the future, corroborate the bleak outlook. Even under the IPCC’s ‘very low’ emissions scenario, which involves a brief overshoot of +1.5°C before stabilizing around +1.4°C by 2100, ice sheets are projected to continue losing mass and contributing to sea-level rise. The paper highlights that even maintaining the climate forcing of 2020 (around +1.1°C to +1.2°C) could lead to over a metre of sea-level rise from Antarctica alone by 2500 if certain instability mechanisms, like Marine Ice Cliff Instability (MICI), are triggered. Professor Stokes emphasized, “Limiting warming to 1.5°C would be a major achievement and this should absolutely be our focus. However, even if this target is met or only temporarily exceeded, people need to be aware that sea level rise is likely to accelerate to rates that are very difficult to adapt to – rates of one centimetre per year are not out of the question within the lifetime of our young people.”
A New, Cooler Target Needed
The study concludes that the current global mean temperature is already too high to maintain the ice sheets in their present state. To avoid catastrophic sea-level rise, the authors hypothesise that a global mean temperature cooler than the present is required, probably closer to +1.0°C above pre-industrial levels, or even lower.
“…land lost to sea level rise from melting ice sheets will be lost for a very, very long time. That’s why it is so critical to limit warming in the first place.”
Prof. Robert M. DeConto, University of Massachusetts Amherst
The researchers stress the imperative of adopting the precautionary principle, given the potentially devastating consequences for coastal populations worldwide and the risk that ice sheet ‘tipping points’ may only become apparent after they have been irrevocably crossed. The findings underscore the urgent need for emissions reductions far exceeding current global ambitions to avert a future with dramatically altered coastlines.
Co-author Professor Robert M. DeConto, from the University of Massachusetts Amherst: “Even if the Earth returns to its preindustrial temperature, it will still take hundreds to perhaps thousands of years for the ice sheets to recover. If too much ice is lost, parts of these ice sheets may not recover until the Earth enters the next ice age. In other words, land lost to sea level rise from melting ice sheets will be lost for a very, very long time. That’s why it is so critical to limit warming in the first place.”
Link to the study: Stokes et al. (2025) Nature Comm Earth Environ 6 (351), Warming of +1.5 °C is too high for polar ice sheets; DOI: https://doi.org/10.1038/s43247-025-02299-w