It is difficult to reverse global warming after "climate overshoot"

A recent paper published by Nature raised concerns about the risk of climate overshoot. Overshoot refers to allowing a temperature rise to temporarily exceed the 1.5 ° C stipulated in the Paris Agreement. Research points out that after climate overshoot, it may be difficult to reverse global warming within the currently envisaged time frame.

The Paris Agreement's optimistic limit on global warming is 1.5 ° C above pre-industrial temperatures. Some people have suggested that it may be possible to temporarily exceed this target and then reduce carbon dioxide emissions to bring the subsequent temperature rise back below 1.5 ° C. However, the impact of this overshoot on climate change has been unclear.

The team of the International Institute for Applied Systems Analysis 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. The team believes that a post-overshoot temperature drop may not be achievable because the amplification of warming caused by stronger Earth system feedback may cause long-term warming.

The team found that after the overshoot, many aspects of the Earth system, such as species abundance, carbon reserves and terrestrial biodiversity, may not return to pre-overshoot levels. Even if the temperature drops after an overshoot, sea levels will continue to rise. They point out that reducing global temperatures is easier to avoid climate risks than trying to stabilize global warming after an overshoot.

The results show that people cannot be overconfident in the controllability of various changes after overshoot, and only rapid reduction of emissions is an effective means to limit climate change.