We have reached a critical moment for the climate. For the first time, a three-year temperature average—2023 through 2025—has exceeded the threshold of 1.5 degrees Celsius of warming over pre-industrial levels set at the Paris climate conference a decade ago. Climate scientists are predicting devastating consequences, just as the world’s governments appear to have lost their appetite for tackling the emissions that cause the warming.
The 1.5-degree target was set to forestall severe weather impacts and potential runaway warming. But 10 years of weak action have followed. “Climate policy has failed. The 2015 landmark Paris Agreement is dead,” says atmospheric chemist Robert Watson, a former chair of the UN’s arbiters of climate science, the Intergovernmental Panel on Climate Change.
Meanwhile, natural stores that soak up our carbon emissions—forests, permafrost, and the oceans—are turning from carbon sinks to carbon sources, accelerating warming. There’s a growing fear that climate change in this new era of overshoot will happen suddenly and unpredictably, as formerly stable planetary systems transgress tipping points that, according to British global-systems researcher Tim Lenton of the University of Exeter, “could transform our world with devastating consequences for people and nature.”
The Atlantic Ocean circulation system, which sustains the Gulf Stream, may be within 30 years of shutdown. The Greenland and West Antarctic ice sheets may have already reached a point of no return. Yet “current policy thinking doesn’t usually take tipping points into account,” notes Manjana Milkoreit of the University of Oslo.
In an analysis for Climate Desk partner Yale Environment 360, I explain how hopes that we can engineer a temperature reset by drawing down carbon emissions after overshoot may prove fanciful. The truth is that the climate system may be about to unleash a period of accelerated warming that is impossible to halt. Overshoot will be permanent.
—Fred Pearce
