PROJECT SYNDICATE: Preparing for Climate Overshoot


Humanity’s continuing failure to reduce greenhouse-gas emissions has substantially increased the likelihood of global warming exceeding 1.5°C within the coming decades. That means we must start exploring a wider set up options for mitigating the worst consequences and managing life in a warmer world.


David McNew/Getty Images
David McNew/Getty Images

PARIS – The latest report from the Intergovernmental Panel on Climate Change revealed what many had feared but were reluctant to admit: the continued failure to reduce greenhouse-gas emissions means that global warming will likely exceed 1.5° Celsius, relative to pre-industrial levels. UN Secretary-General António Guterres has warned that this key goal of the 2015 Paris climate agreement is now on “life support.” Even if emissions “peak before 2025 at the latest,” notes the IPCC, and are “reduced by 43% by 2030” (including a one-third reduction in methane), “it is almost inevitable that we will temporarily exceed this temperature threshold but could return to below it by the end of the century.”


If avoiding a breach of 1.5°C is still technically possible, we should of course not give up. But the window of opportunity is closing faster than we thought, and deepening geopolitical divisions – intensified by the pandemic, Russia’s aggression against Ukraine, and looming food, energy, and debt crises – do not augur well for the kind of cooperation that we need.


By surpassing 1.5°C, but then taking measures to bring temperatures back below that threshold by the end of the century, we will be in what the IPCC calls an “overshoot” scenario. Although climate models have long accounted for this possibility, not much is known about how to reduce the risks – both environmental and political – that it would create.


Average global temperatures have already risen 1.1°C above pre-industrial levels, with significant environmental effects. Every additional tenth of a degree contributes further to the severity and frequency of extreme weather events and increases the risks to health, food, water, livelihoods, and biodiversity. By the time we reach 2°C, many human and natural systems will be under extreme stress; some ecosystems will struggle to survive, and others already will be gone.


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