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© pixabay.com | TheDigitalArtist- | “We know least about the scenarios that matter most”, Dr Luke Kemp

Considering catastrophe: high-impact, low-probability climate scenarios “dangerously underexplored”

Researchers call for a new “Climate Endgame” agenda and say far too little work has gone into understanding the mechanisms by which rising temperatures might pose a “catastrophic” risk to society and humanity.

For instance if temperature rises are worse than many predict or cause cascades of events we have yet to consider, or indeed both. The world needs to start preparing for the possibility of a “climate endgame”, the authors argue in a perspective piece in the Proceedings of the National Academy of Sciences PNAS. Assessing catastrophic risks is necessary in order to have a better chance of preventing them.

“Irreversible and potentially catastrophic risks caused by human induced climate change must be factored into our planning and actions. If there is a red thread in science over the past 30 years it is this; the more we learn about how our planet functions, the higher is the reason for concern”, Johan Rockström explains, Director of the Potsdam Institute for Climate Impacts and a co-author, “Tipping points are coming closer, not only because we are emitting more greenhouse gases, but also that we increasingly understand that our planet is more fragile and a more sophisticated organism with feedbacks and interactions that quite abruptly can shift its functions from dampening and cooling, to amplifying and warming. Amazon die-back and accelerated melting of the Greenland ice sheet are examples of systems that can rapidly go from cooling sinks to warming sources. This means we cannot contend ourselves to look at mean values only, we must factor in non-linear high-end risks. Key is to do the math of disaster, in order to avoid it.”

“There are plenty of reasons to believe climate change could become catastrophic, even at modest levels of warming,” said lead author Luke Kemp from Cambridge’s Centre for the Study of Existential Risk. “Climate change has played a role in every mass extinction event. It has helped fell empires and shaped history. Even the modern world seems adapted to a particular climate niche,” he said. “Paths to disaster are not limited to the direct impacts of high temperatures, such as extreme weather events. Knock-on effects such as financial crises, conflict, and new disease outbreaks could trigger other calamities, and impede recovery from potential disasters such as nuclear war.”

The author team proposes a research agenda focusing on what they call the “four horsemen” of the “climate endgame”: famine and malnutrition, extreme weather, conflict, and vector-borne diseases. Rising temperatures pose a major threat to global food supply, they say, with increasing probabilities of “breadbasket failures” as the world’s most agriculturally productive areas might suffer collective meltdowns. Hotter and more extreme weather could also create conditions for new disease outbreaks as habitats for both people and wildlife shift and shrink. Furthermore, focus on identifying all potential tipping points within “Hothouse Earth” should be strengthened, say researchers: from methane released by permafrost melts to the loss of forests that act as “carbon sinks”, and even potential for vanishing cloud cover.

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Potsdam-Institut für Klimafolgenforschung 2022

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