Understanding climate tipping must be prioritized

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Evidence is mounting that the Earth’s climate system can change abruptly when tipping points are crossed, for example by anthropogenic release of greenhouse gases. We urgently need to understand and predict these abrupt transitions better.

Abrupt climate change on the Mont Blanc. Glaciers are receding on the white mountain. Credit M. Ghil.

A list of priorities for the study of climate tipping is presented in the article ”Theoretical and paleoclimatic evidence for abrupt transitions in the Earth system” published in the journal Environmental Research Letters by Niklas Boers, Technical University of Munich, Germany, Michael Ghil, Ecole Normale Supérieure de Paris, France, and Thomas Stocker, Climate and Environmental Physics and Oeschger Centre of Climate Change Research, University of Bern, Switzerland.

The authors call for a special report on tipping points by the IPCC. They argue that climate tipping has happened many times in the Earth’s history and is likely to happen in response to anthropogenic warming. Therefore, this issue needs to be addressed energetically in all areas of climate science.

”Our theoretical understanding of the climate system suggests that abrupt climate transitions are possible and this is confirmed by evidence from paleoclimate records. However, the critical CO2 and temperature levels remain highly uncertain and we urgently need further research to better constrain them,” says Niklas Boers.

Broken records everywhere

Assessments by the IPCC are based on large, complex climate models which mostly predict that climate change manifests itself as a smooth, gradual transition to a warmer climate. However, these models are likely to underestimate the dynamic nature of the climate system.

”We see records, such as heat, drought, flooding, broken everywhere. That is not the way you’d expect climate change to be according to the state-of-the-art climate models,” says Michael Ghil.

If current greenhouse gas emissions indeed lead to abrupt rather than to gradual climate change, then the science and the current climate models are not well suited to accurately predict when and how such transitions will happen.

This is partly because the understanding of why and how abrupt transitions take place in the current climate is not fully developed. But it is also due to the fact that only a fraction of climate scientists understand and work with the theories describing climate tipping.

”The science behind climate tipping points is still in its infancy and we need to improve our climate models a lot to be able to more accurately simulate the response of critical components of the Earth system under accelerating global heating,” adds Thomas Stocker.

Focus points

All in all, the situation calls for climate science to urgently step up and improve the overall understanding and modelling of climate tipping. The authors provide the following recommendations:

– The Intergovernmental Panel on Climate Change should prepare, in its next assessment cycle, a special report on the ”Climate Tipping Points and Consequences for Habitability and Resources”. Such an assessment would provide the much-needed scientific consensus on an issue of key policy relevance.

– Critical chokepoints of the Earth System must be more closely monitored, in particular the Greenland and West Antarctic ice sheets, tropical monsoon systems, the ocean circulation system in the Atlantic Ocean known as the AMOC, as well as boreal forests and the Amazon rainforest. Such monitoring efforts would enhance our chance to detect early warning signals of tipping.

– The authors identify the immediate need for more systematic use of climate models in terms of further improving high-end Earth system models as well as paying much greater attention to simpler and more flexible models that permit a better exploration of how details in a climate subsystem might trigger tipping.

– Finally, the authors suggest that economic models of climate change would account for the possibility of tipping so as to more appropriately assess economic risks and costs associated with anthropogenic climate change.