New study assesses climate overshoot risk: reversing global warming within the expected time frame may be difficult

A recent climate change paper published by the internationally renowned academic journal Nature stated that researchers have raised concerns about the increasing use and acceptance of climate overshoot scenarios, which means allowing temperature rises to temporarily exceed the 1.5°C specified in the Paris Agreement. After climate overshoot, it may be difficult to reverse global warming within the current envisaged time frame.

The authors believe that in fact, limiting global warming may be the most effective strategy to mitigate climate change.

According to the paper, the Paris Agreement limits optimism on global warming to 1.5°C higher than pre-industrial temperatures. It has been suggested that it may be possible to temporarily exceed this goal, known in the technical term as "overshoot", and then reduce carbon dioxide emissions to bring the subsequent temperature rise back below 1.5°C (although this may depend on the development of carbon capture technology). However, the impact of overshoot on climate change has been unclear.

Based on this, the first author and corresponding author of the paper, Carl-Friedrich Schleussner of the International Institute for Applied Systems Analysis in Austria, and colleagues and collaborators conducted model simulations of overshoot paths and long-term climate stability. They found that global and regional climate change risks vary depending on scenarios in which overshoot occurs or does not occur. At the same time, a temperature drop after an overshoot may not be achievable because the amplification of warming caused by stronger Earth system feedback may cause long-term warming.

This study also found that after an overshoot, many aspects of the Earth system, such as species abundance, carbon reserves and terrestrial biodiversity, may not return to pre-overshoot levels. The authors emphasized that even if the temperature drops after the overshoot, sea levels will continue to rise. Therefore, it is easier to avoid climate risks by reducing global temperatures than by trying to stabilize global warming after an overshoot.

The authors point out that the overshoot scenario relies on the likelihood that future carbon removal costs will fall relative to current costs. Any preventive carbon capture system that can be developed will need to remove approximately hundreds of billions of tons of carbon after overshoot to avoid high-risk outcomes. However, current technical, economic and sustainability considerations may make it difficult for such systems to operate at these levels.

"Nature" published a "News and Opinions" article by peer experts at the same time. The research results show that people cannot be overconfident in the controllability of various changes after overshoot. Only rapid reduction of emissions is an effective means to limit climate change.