Last year’s record warmth is likely to be part of a long-term shift to average temperatures of above 1.5 degrees rather than being a one-off, according to a major international study published on Monday.
In a separate but related study scientists suggest the 12 months at 1.5 degrees “signals earlier than expected breach” of the Paris climate agreement, while exceeding that threshold will be inevitable without a step change in efforts to cut greenhouse gases.
Both studies were published in Nature Climate Change and indicate the key Paris temperature target set in 2015 to minimise climate disruption across the planet is likely to be breached in coming years.
Exceeding 1.5 degrees in the long-term heightens risk of irreversible impacts on Earth and increasingly catastrophic effects across the planet – notably a worsening of extreme weather events.
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The studies were led by Dr Emanuele Bevacqua of Helmholtz Centre for Environmental Research in Germany and Dr Alex J Cannon of the research division in Environment and Climate Change Canada.
“A year above 1.5 degrees signals that Earth is most probably within the 20-year period that will reach the Paris Agreement limit,” the Bevacqua study concludes.
Reacting to the findings, UK Met Office chief scientist Prof Stephen Belcher said: “A single year of exceedance of 1.5 degrees does not break the guardrail of the Paris agreement. However, it does highlight that the headroom to stay below 1.5 degrees is now wafer thin.”
A Met Office forecast for the coming year has predicted levels of “atmospheric concentration of CO₂ is now inconsistent with pathways keeping to 1.5 degrees [and] only rapid and strong measures to cut greenhouse gas emissions will keep us from passing the first line of defence within the Paris agreement”.
To determine whether the Paris pact has failed is defined as two decades above 1.5 degrees and not one year as we have just had, due to natural climate variability, said Daniela Schmidt, professor of earth sciences at the University of Bristol. “These papers suggest the forcing conditions have been reached now, and we reached the decade in which the Paris agreement will be broken,” she said.
“These are important papers exploring when 1.5-degree 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 1.5 degrees, she said, “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 3-degree warming globally, locally much more. Such warming has immense and in parts irreversible consequences for nature and people”.
Dr Richard Hodgkins, a specialist in climate futures at Loughborough University, said analysis in both papers showed the record warmth of 2024 is likely to be part of a long-term shift.
“However, this doesn’t mean that the Paris agreement target of 1.5 degree is dead, because the ‘net zero pathway’ to 1.5 degrees 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 1.5 degrees is not dead.”
However, the anticipated decline of temperatures relied on the assumption large-scale technologies to remove carbon-dioxide from the atmosphere will be rapidly developed, globally deployed, and operate successfully, which is speculative to say the least, he said.
“So in that sense 1.5 degrees 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 1.5 degrees 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.”
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