February 10, 2025

expert reaction to two papers assessing the impact of 2024 temperatures on Paris Agreement targets

Two papers published in Nature Climate Change look at the impact of 2024 temperatures on Paris Agreement targets (1.5 degrees). 

Dr Akshay Deoras, Research Scientist, National Centre for Atmospheric Science and the Department of Meteorology, University of Reading, said:

“The two papers help reflect the fact that we are getting dangerously close to breaching the Paris Agreement. Well-defined methodologies have been used, and conclusions are backed by solid data. However, a key limitation of these studies is that the models used might not account for all factors influencing global warming. This means that some uncertainty remains regarding whether the Paris Agreement will be breached in the late 2020s, early 2030s, or even earlier. This uncertainty should not be used as an excuse to continue business as usual, since the goal to limit global warming to 1.5°C is certainly dead in the absence of a rapid and robust reduction in emissions. Governments must urgently strengthen their commitments, align policies with science, and accelerate the transition to a sustainable future. The world cannot afford to abandon the Paris framework at this stage; instead, we must reinvigorate it with ambition and accountability.”

Dr Robin Lamboll, Research Fellow at the Centre for Environmental Policy, Grantham Institute – Climate Change and Environment, Imperial College London, said: 

“These two papers show that we are already in a time of peril for the 1.5°C target.  

“There is a subtle distinction between what they show and what you might assume: they show that IF we are in a scenario that exceeds 1.5°C, the time of exceedance has very likely already started.  

“The work by Cannon does not investigate scenarios where we never exceed 1.5°C, and the work by Bevacqua states that, in a scenario where we risk but aren’t committed to exceeding 1.5°C, we are “likely” but not “very likely” to exceed 1.5°C in the long term (so, more than 66% but less than 90% chance), now that we have seen a single year above 1.5°C warming.” 

Professor Stephen Belcher, Met Office chief scientist, said:

“A single year of exceedance of 1.5°C does not break the guardrail of the Paris Agreement. However, it does highlight that the headroom to stay below 1.5°C is now wafer thin. In a recent paper a collection of Met Office scientists calculated that the current global warming level is 1.3°C above pre-industrial levels. Added to this a Met Office forecast of carbon dioxide for the coming year reveals that the atmospheric concentration of CO₂ is now inconsistent with pathways keeping to 1.5°C; this suggests that only rapid and strong measures to cut greenhouse gas emissions will keep us from passing the first line of defence within the Paris Agreement.”

Dr Alan Kennedy-Asser, Senior Research Associate at the University of Bristol Cabot Institute for the Environment, said:

“I find the results of this modelling study to be, sadly, unsurprising and I would agree that the evidence suggests that 2024 (and now 2025) will be within a 20 year period which has an average temperature at or above 1.5°C unless something very radical changes in the next 5 to 10 years, suggesting we may be already living in the 1.5°C world the Paris Agreement referred to. Another way to think about this is that the year 2024 exists within 20 different climatology periods (one starting at 2024, one ending at 2024). The period ending 2024 is not above 1.5°C, however I would be very confident the one beginning in 2024 will be above 1.5°C unless something very radical changes in the next 5-10 years (in agreement with these papers). Meanwhile somewhere between these two will be the closest that one period is to precisely 1.5°C (perhaps the period 2018-2037 – we shall find out).

“Both studies use straightforward but, in my opinion, sensible methodologies and use the most suitable data currently available: these are precisely the research questions CMIP6 models are designed to answer. However, even though the planet may be in a period that is at or exceeds 1.5°C, there is great value in taking rapid action to slow further warming, as the rate of change matters and every tenth of a degree matters.

“I believe the press release is an accurate representation of the papers.”

Prof Daniela Schmidt, Professor of Earth Sciences, University of Bristol, said:

“To determine whether the Paris agreement has failed is defined as two decades above 1.5C and not one year as we have just had, due to natural climate variability. These papers suggest that the forcing conditions have been reached now, and that we reached the decade in which the Paris agreement will be broken. They came to this conclusion by interrogating climate models and observed temperature anomalies in complex discussions about probabilities and model baselines.  These are important papers exploring when 1.5C warming is passed, given the impacts projected and the need for adaptation to reduce risk.

“The key importance of the Paris agreement is to avoid risk. Every increment of warming avoided by dramatically increasing mitigation reduces the risks and impacts of human driven changes to our climate system on people, our cities, our infrastructure and the environments which support us.

“Fixating on a number of 1.5C, and that if will be surpasses, has the real risk of reducing actions, demotivating all of us – people, civic society, industry – to give up on trying. The consequence of a lack of ambition is that we will stay on the warming pathways we are currently on, which leads to nearly 3C warming globally, locally much more. Such warming has immense, and in parts irreversible consequences for Nature and people.

“So while breaching 1.5C is not good news, reducing action and reaching twice as much warming is clearly much worse.”

Prof Richard Allan, Professor of Climate Science, University of Reading, said:

“A single year being globally 1.5 degree Celsius warmer than preindustrial levels does not mean we have crossed the Paris climate agreement threshold but it does mean breaching this dangerous level is pretty much inevitable.

“The threshold of 1.5 degree Celsius above preindustrial climate decided at the Paris climate agreement applies to the global surface temperature averaged over multiple decades so a single year doesn’t mean we have breached this dangerous level. But given that warming of climate is accelerating, it is common sense that if a year unaffected by additional warming influences such as El Niño crossed this boundary it is pretty certain that crossing the 1.5 degree threshold will be inevitable without a step change in efforts to cut greenhouse gases. The new studies robustly confirm that even accounting for El Niño warmth, the persistence and magnitude of global temperatures in 2024 mean that to all intents and purposes breaching the 1.5 degree threshold is a given and that we need to double down efforts to avoid the even more dangerous 2 degree Celsius threshold by rapidly and massively cutting greenhouse gas emissions.”

Dr Richard Hodgkins, a Reader in Climate Futures at Loughborough University, said:

“While individual years may always be warmer or cooler than long-term averages, the analysis in both papers show that the record warmth of 2024 is likely to be part of a long-term shift above 1.5C, rather than being a one-off. However, this doesn’t mean that the Paris Agreement target of 1.5C is dead, because the Net Zero pathway to 1.5C always assumed that temperatures would increase above that target, before coming back down in the second half of the current century. So, in that sense, 1.5C is not dead.

“However, the anticipated decline of temperatures relies on the assumption that large-scale technologies to remove carbon dioxide from the free atmosphere will be rapidly developed, globally deployed, and operate successfully, which is speculative to say the least. So, in that sense, 1.5C is dead because achieving it relies on borderline science fiction. There are many who would say that the reliance on carbon dioxide removal meant that 1.5C was never a very plausible target in the first place. Regardless, it shows that focusing on targets and not actions is an ineffective approach, and that actual emissions reductions, which can be achieved with existing, successful technologies, are needed now.”

Dr Vikki Thompson, Scientist at the Royal Netherlands Meteorological Institute, said:

“These studies use data from both observational sources and multiple climate models to show we should now expect to exceed the Paris Agreement within the next 20 years, much sooner than climate projections had suggested. With this January continuing the recent trend, becoming yet another hottest on record month, we have seen 18 of the last 19 months exceeded 1.5C above pre-industrial. Not quite the 18 consecutive months shown by Cannon to make it virtually certain we will exceed the Paris Agreement, but so very close. 

“The rate we have reached these levels is terrifying and shows, yet again, how urgently we need to act. Without adaptation and mitigation we will continue to feel the impacts of the accelerating warming with more and more extreme weather events.”

Paper 1:

‘A year above 1.5 °C signals that Earth is most probably within the 20-year period that will reach the Paris Agreement limit’ by Emanuele Bevacqua et al. was published in Nature Climate Change at 16:00 UK time on Monday 10 February 2025.

DOI: 10.1038/s41558-025-02246-9

Paper 2:

‘Twelve months at 1.5 °C signals earlier than expected breach of Paris Agreement threshold ‘ by Alex J. Cannon et al. was published in Nature Climate Change at 16:00 UK time on Monday 10 February 2025.

DOI: 10.1038/s41558-025-02247-8

Declared interests

Prof Richard Allan: No conflicting interests

Dr Vikki Thompson: No interests to declare.

Dr Akshay Deoras: No conflicts to declare.

For all other experts, no response to our request for DOIs was received.