We’re likely to breach 1.5C. What happens next is still in our hands

A recent report from the United Nations highlights that surpassing the Paris Agreement’s climate target of limiting global warming to 1.5°C above pre-industrial levels is now likely inevitable in the coming years. However, the degree to which temperatures exceed this boundary, the duration of this overshoot, and the potential for temperatures to eventually decline are all outcomes still influenced by decisions made today. The report offers a nuanced view that crossing this threshold does not render further climate action pointless.

For nearly ten years, 1.5°C has been regarded as a critical limit in climate policy to prevent the most severe impacts of global warming. The UN Environment Programme (UNEP), in its newly published “Limiting Overshoot” report, outlines a possible pathway where global temperatures temporarily rise above 1.5°C before peaking and then declining as emission levels drop and net carbon removal increases. According to the analysis, under the most optimistic scenario, the warming would reach about 1.8°C mid-century. Present policies, however, are anticipated to push global temperatures to roughly 2.6°C by 2100. This stark contrast underscores the importance of every fraction of a degree in temperature avoided to reduce harm.

Scientists emphasize that the 1.5°C threshold should not be seen as a strict dividing line between safety and disaster. Risks gradually worsen as temperature rises incrementally above this mark. University of Victoria climate scientist Andrew Weaver, who was not involved in UNEP’s work, explained to the Associated Press, “The 1.5 limit is not ‘some magical climate cliff’ where it’s just game over. Every tenth of a degree we avoid still means less damage.” While 2024 may have been the first year with average temperatures exceeding 1.5°C, the Paris target is evaluated over multi-year averages, and current sustained warming is around 1.4°C. Nevertheless, the UNEP report signals that crossing the limit in the near future is highly probable.

The report further stresses the importance of minimizing both the peak level of warming and the time spent above the target. Mirey Atallah, chief of UNEP’s adaptation and resilience branch and the report’s coordinator, stated: “Decisions, science and, most importantly, mindsets need to shift to seeing 1.5°C as a goal we’ll be approaching from above rather than below.” To bring temperatures back below 1.5°C, the report highlights the necessity of massive and prolonged reductions in fossil fuel emissions, accompanied by net-negative emissions achieved through natural methods like forest restoration and emerging carbon capture technologies. Importantly, UNEP cautions that removing carbon cannot replace immediate emissions cuts, and that some consequences of overshoot, such as damage to ice sheets, the Amazon rainforest, and sea level rise, may be irreversible. As climate scientist Richard Betts from the University of Exeter summarized, “It’s a reality check. We have to live with this warmer world. But there’s still a lot we can do to limit warming.”

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