Climate change: Top five greenhouse gas emitters set to exacerbate regional heat extremes

Greenhouse gas emissions from the top five contributors – China, the US, the European Union, India and Russia – are expected to increase the probability of extreme hot years by 2030, according to a modelling study published online in Communications Earth & Environment. Under current climate change mitigation pledges, emissions from these regions could double the number of countries experiencing extremely hot years every other year, relative to scenarios without emissions from the top five contributors.

Updated pledges towards mitigating climate change were presented ahead of COP26 in Glasgow in November 2021, but these pledges still fall short of the goal of the 2015 Paris Agreement to limit global warming to 1.5°C over pre-industrial levels. The Glasgow Climate Pact called upon parties to strengthen their commitments by the end of 2022. However, the implications of a shortfall in climate mitigation ambition have mainly been investigated at a global level, rather than at the scale of individual countries.

Lea Beusch and colleagues translated historical emissions data, combined with pre-COP26 pledges from the five largest emitters, into projected country-level warming by 2030. They found that under current pledges, 92% of the 165 countries studied are expected to experience extremely hot years, which only occurred about once per century in a pre-industrial climate, at least every other year, compared to 46% without the influence of the top five emitters. The latter estimate is made based on a scenario excluding emissions from the top five contributors after 1991, the point in time when the Intergovernmental Panel on Climate Change (IPCC) first informed policy makers of human-made climate change.

The results highlight the importance of the emissions reduction ambitions by the top five emitters for the emergence of regional climate change, including hot extremes, over the next decade.