Ten years ago, world leaders in Paris committed to limiting global warming to well below 2°C above pre-industrial levels, while pursuing efforts to limit it to 1.5°C. Since then, the average global temperature was recorded above 1.5°C for the first time in 2024, prompting questions about the relevance of this target.
However, a new report from Climate Analytics clarifies that the Paris Agreement’s goals remain relevant, despite the overshooting of 1.5°C. Indeed, it calls for the implementation of the agreement to be strengthened. The report unveils a new “highest possible ambition” scenario that allows the overshoot of temperature above 1.5°C for 40 years, peaking at around 1.7°C. After this period, the temperature should gradually be reduced to around 1.2°C by 2100, ultimately meeting the Paris Agreement target.
The report asserts that the Paris Agreement does not exclude the possibility of a limited overshoot of 1.5°C.
Whilst meeting +1.5°C, even after a brief overshoot, would be an incredible achievement, Professor Chris Stokes from Durham University, warns that it might be too high to prevent several metres of sea level rise from the world’s polar ice sheets in Greenland and Antarctica, which together store almost 65m of sea level. His research, entitled “Warming of +1.5°C is too high for polar ice sheets,” strongly suggests that even temporary overshoots of the 1.5°C target can result in very high rates of global mean sea level (GMSL) rise.
The research highlights that the current climate of +1.2°C above pre-industrial is already generating substantial mass loss since the 1990s, and that the sea-level rise may subsequently increase by several metres over the coming centuries. As a result, the research proposes limiting the target closer to +1°C for polar ice sheets.
Though his research focuses on polar ice, the resulting sea-level rise has global consequences, as sea level is a key indicator of climate change. Indeed, the latest news involving more than 3,000 Tuvaluans seeking climate visas in Australia, due to the ongoing submerging of much of the island nation, clearly demonstrates the interdependence between climate change and human rights, including rights to a healthy environment and cultural identity.
To better understand these findings and their implications, JURIST spoke with Professor Stokes. A recipient of the Philip Leverhulme Prize and the British Society for Geomorphology’s Gordon Warwick Medal, Stokes has published over 150 papers in peer-reviewed journals and advises policymakers at COP meetings.
JURIST: The new report by Climate Analytics suggests that a temporary increase in global temperature above 1.5°C for 10–20 years still aligns with the Paris Agreement, provided the temperature is later reduced to around 1.2°C by 2100. Given the current trend of extreme weather events, such as droughts and wildfires, driven by climate change, how feasible is it to implement this ‘highest possible ambition’ scenario in practice?
Stokes: This is a difficult question to answer and one which you may need to ask governments around the world. Although the year 2024 was, on average, warmer than +1.5°C, that does not constitute a breach of the limit. Instead, the limit is based on a 20-year average, i.e. the average temperature over 20 years would have to exceed +1.5°C. The precise year of exceedance is then defined by the mid-point of that 20 -year period. So, if the 20-year period from 2020 to 2040 = +1.5°C, then we would only be able to know/confirm that in 2040, but the year of exceedance would actually be 2030.
It is very clear that there has been a distinct lack of ambition since the Paris Agreement was signed and that we are now looking at an ‘overshoot’ scenario, where we breach the limit, probably in the next few decades, but then have to return to +1.5°C or lower as soon as possible. It must remain our target and focus because the longer we exceed it and the higher the temperatures increase, the worse the effects will be, and the higher the costs to deal with those effects. This was re-emphasised by the International Court of Justice (ICJ), in its recent Advisory Opinion on climate change, that countries have a legal duty to collectively secure the Paris Agreement’s +1.5 °C limit, for example, through being very ambitious in their nationally-determined contributions (NDCs).
The good news is that the new report shows that global warming can be halted in the next 15 to 20 years and return below +1.5°C by 2100 in line with the Paris goal of +1.5°C. In this ‘highest possible ambition’ scenario, temperatures exceed +1.5°C for 40 years and peak at around +1.7°C, before declining to ~+1.2°C by 2100.
The real strength of the Climate Analytics report is that it demonstrates that it is still possible to limit both the duration and the peak of the overshoot and then return to +1.5 and below. However, this requires a rapid phase out of fossil fuels and scale-up of carbon dioxide removal, underpinned by the technological revolution in renewables and electrification. It’s clear that some countries will find it very difficult to wean themselves off fossil fuels but this really is our only hope and, collectively, it will require countries to work together.
JURIST: Could you briefly explain how you arrived at the 1°C threshold for polar ice sheets in your research, and why you believe the target should be closer to 1°C?
Stokes: Our research only focussed on the polar ice sheets in Greenland and Antarctica and their recent and future contribution to sea-level rise. We are really worried that these big ice sheets – which together store nearly 65 metres of sea-level rise – are already losing ice very rapidly, even at today’s level of warming, which is +1.2°C. In fact, they are losing around 400 billion tonnes of ice per year! Thus, it’s very clear to us that +1.5°C is too high for ice sheets and that you would have to return to cooler than present conditions to slow or stop sea-level rise. We hypothesize that this may be around +1.0°C but there is a lot of uncertainty in what might be considered a ‘safe’ limit and it might even be lower. We need to do some more modelling of how ice sheets respond to lower than present temperatures. It may already be too late for parts of West Antarctica and Greenland but every fraction of a degree really matters, and the ‘highest possible ambition’ scenario (described above) is our best bet to return to a safe limit as quickly as possible.
JURIST: How would the proposed +1°C target work within the existing framework of the Paris Agreement? Was your research a call to recalibrate our ambition for polar ice sheet stability, or is it better understood as a scientific warning to keep the temperature within a safe zone?
Stokes: This is not really my area of expertise and you might have to ask someone more familiar with climate law, but I think there may be scope under what is called the ‘Periodic Review’ of the Paris Agreement. Under the UNFCCC, Parties agreed to periodically review the adequacy of the long-term global goal and the progress towards achieving it.
We are not advocating separate targets for ice sheets. The key metric is the mean global temperature and scientists then look at how that might impact the various regions around the world. We know, for example, that the Arctic is warming around 3 times faster than the global average but that other parts of the world are warming at a lower rate than the global average. The key thing is that every fraction of a degree really matters and the quicker we can slow and halt the warming, the safer it will be for humanity.
Clearly, our immediate focus must be on limiting warming to +1.5°C but there may be a situation where Parties want to review the adequacy of this target.
JURIST: Could you explain why sea-level rise is significant to climate change, particularly to small island nations?
Stokes: 230 million people live within 1 m of sea level rise and 1 billion live within 10 metres. Even under current warming (+1.2 °C), sea level rise is accelerating and could reach 1 cm per year by 2100, if recent trends were to continue. 1 cm per year would mean 1 m per century and that would lead to major disruption at a global scale because it becomes very challenging to adapt to those rates of sea level rise and people living on coastal regions will simply have to move. Of course, the low-lying small island states are especially vulnerable and sea level rise represents an existential threat to some countries. And let’s not forget that these countries are not to blame for climate change – the sense of injustice is profound.
JURIST: What are your key takeaways from COP30 that took place in Brazil?
Stokes: I always come away from COPs with mixed feelings and a lot of frustration. COPs receive a lot of criticism, some of which might be deserved, but the world would be in a much worse place if they were not taking place. At one point, it was plausible that we might have seen warming approach 4°C by the end of century but current policies and action are likely to bring that to below 3°C and possibly as low as 2.5°C.
This is still far too high, of course, but with the highest possible ambition, it is possible to reduce warming to below 2°C and then come back down to safer levels. Sadly, and despite some optimism before COP30, it failed to deliver its roadmap for the phase-out of fossil fuels but it did reaffirm its commitment that 1.5 °C should be the long-term temperature target. There were also some positive outcomes in terms of a new mechanism to ensure a Just Transition away from fossil fuels and a tripling of finance for adaptation to climate change.
Professor Chris Stokes currently teaches modules on climate change, glaciers and glaciation and the Arctic at Durham University. He has published over 150 papers in international peer-reviewed journals, in addition to numerous invited book chapters and Encyclopedia entries. These research contributions have been recognised through a Philip Leverhulme Prize (2009) and the British Society for Geomorphology’s Gordon Warwick Medal (2013). Chris has also won a University award for Excellence in Doctoral Supervision (2016) and a Green Gown Award for innovation in Education (2021).
