By Peter Ngare
A new study finds that temporarily exceeding the global temperature rise of 1.5°C is likely to have long-term consequences. The research, by 30 scientists published on October 9, 2024, in Nature, found that such an overshoot has irreversible consequences and that rapid near-term emission reductions are essential to reducing climate risks.
The study points to severe outcomes such as rising sea levels, local species extinctions, the melting of permafrost, and the degradation of northern peatlands. These changes, in turn, would accelerate global warming by releasing methane—one of the most potent greenhouse gases—into the atmosphere. The findings emphasize that while bringing temperatures back down after an overshoot is theoretically possible, many irreversible consequences will remain, such as lost biodiversity and changes in critical carbon sinks.
Senior author Professor Joeri Rogelj, Director of Research at Imperial College London’s Grantham Institute, explained the distinction between two different climate futures: one where global warming temporarily surpasses 1.5°C and one where it does not.
“A world that has overshot 1.5°C will look different to one that didn’t, even if both reach the same temperature in the long run. Until we get to net zero emissions, warming will continue. The earlier we can get to net zero, the lower peak warming will be, and the smaller the risks of irreversible impacts,” said Rogelj.
The 2015 Paris Agreement enshrined the 1.5°C warming limit above pre-industrial temperatures as a critical goal to avoid catastrophic climate impacts. Achieving this goal requires net-negative carbon emissions, which demand a combination of reducing fossil fuel use and developing large-scale carbon removal technologies. However, the researchers argue that even temporary overshooting of this target could alter the Earth system in ways that cannot fully be undone.
The study highlights that key aspects of the Earth’s systems—such as species abundance, biodiversity, and carbon stocks—may not recover to pre-overshoot levels once they’ve been altered. The implications for ecosystems could be profound, potentially leading to permanent shifts in species populations and the degradation of ecosystems essential for carbon storage. However, the scientists stress that any decline in global temperature, even after an overshoot, will still play a significant role in reducing long-term climate risks, particularly regarding sea-level rise and ice sheet stability.
In light of these findings, the team called for immediate and aggressive action to curb emissions. They reiterated that delayed efforts would significantly increase the risks associated with overshooting the 1.5°C threshold.
“Our work reinforces the urgency of governments acting to reduce our emissions now, and not later down the line. The race to net zero needs to be seen for what it is – a sprint,” the researchers concluded.
This study adds to the growing body of research demonstrating that limiting warming to 1.5°C is not just an arbitrary goal but a vital one for preserving ecosystems, preventing extreme weather events, and securing the future for generations to come.
