Overshoot: The World Is Hitting Point of No Return on Climate - Yale E360

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The 2024 Park Fire near Chico, California.<br>David McNew / Getty Images

the world is poised to overshoot the goal of limiting average global warming to 1.5 degrees celsius, as for the first time, a three-year period, ending in 2025, has breached the threshold. and climate scientists are predicting devastating consequences, just as the world’s governments appear to have lost their appetite for tackling the emissions that are causing the warming. the 1.5-degree target was set at the paris climate conference a decade ago, at the insistence of more vulnerable nations, to forestall severe weather impacts and potential runaway warming that could lead to exceeding irreversible planetary tipping points. but climate scientists say that 10 years of weak action since mean that nothing can now stop the target being breached. “climate policy has failed. the 2015 landmark paris agreement is dead,” says atmospheric chemist robert watson, a former chair of the u.n.’s arbiters of climate science, the intergovernmental panel on climate change (ipcc).meanwhile, a picture of what lies ahead is becoming clearer. in particular, there is a growing fear that climate change in the future won’t, as it has until now, happen gradually. it will happen suddenly, as formerly stable planetary systems transgress tipping points — thresholds beyond which things cannot be put back together again. "><br>The world is poised to overshoot the goal of limiting average global warming to 1.5 degrees Celsius, as for the first time, a three-year period, ending in 2025, has breached the threshold. And climate scientists are predicting devastating consequences, just as the world’s governments appear to have lost their appetite for tackling the emissions that are causing the warming.<br>The 1.5-degree target was set at the Paris climate conference a decade ago, at the insistence of more vulnerable nations, to forestall severe weather impacts and potential runaway warming that could lead to exceeding irreversible planetary tipping points. But climate scientists say that 10 years of weak action since mean that nothing can now stop the target being breached. “Climate policy has failed. The 2015 landmark Paris agreement is dead,” says atmospheric chemist Robert Watson, a former chair of the U.N.’s arbiters of climate science, the Intergovernmental Panel on Climate Change (IPCC).<br>Meanwhile, a picture of what lies ahead is becoming clearer. In particular, there is a growing fear that climate change in the future won’t, as it has until now, happen gradually. It will happen suddenly, as formerly stable planetary systems transgress tipping points — thresholds beyond which things cannot be put back together again.

“Nature has so far balanced our abuse,” says Johan Rockström, a leading Earth systems scientist. “This is coming to an end.”

“We are rapidly approaching multiple Earth system tipping points that could transform our world with devastating consequences for people and nature,” says British global-systems researcher Tim Lenton, of the University of Exeter. If he and other scientists are right, then hopes currently being expressed of a temperature reset by reducing emissions after overshoot may be fanciful. Before we know it, there may be no way back.<br>The effects of imminent 1.5-degree overshoot are already apparent in a rising tide of weather catastrophes: soaring heatstroke deaths in India, Africa, and the Middle East; unprecedented wildfires in the United States; and escalating property damage and floods from tropical storms and extreme precipitation.

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Last year, Bailing Li of NASA’s Goddard Space Flight Center disclosed that her agency held un-peer reviewed data showing a dramatic increase in the intensity of the world’s weather in the past five years. Meanwhile, the International Chamber of Commerce reported that extreme weather linked to the changing climate had cost the global economy more than $2 trillion in the past decade and damaged the lives and livelihoods of a fifth of the world’s population.<br>But that is just the start. Climate change is gathering pace. The last three years have been the hottest on record, with both 2023 and 2025 nearly reaching 1.5 degrees above preindustrial levels, and 2024 hitting 1.55 degrees.

Average global temperature compared to the preindustrial average. Source: Copernicus Climate Change Service.<br>Yale Environment 360 / Made with Flourish

A three-year breach of 1.5 degrees does not mean we have broken the Paris limit, which is framed as a long-term average. Conventionally, scientists measure this over 20 years, to smooth out year-on-year aberrations caused by natural cycles such as the El Niño oscillation. Using this method, it will be several more years before researchers can say for certain if warming has...