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Climate scientists: We know too little about the risk of the end of humanity

How can extreme climate change interact with all other risk factors that already threaten human life? There is not enough research into this question, according to an international group of researchers. Illustration: Bigstock

Today, 30 million people live in extremely hot areas with a mean annual temperature of 29 °C. If the global mean temperature rises unchecked, two billion people will live in similar conditions in 2070. In the most vulnerable areas, many countries are today already facing challenges such as political instability, widespread poverty, and famine. But what will happen if extreme climate change is added to the list of problems? What is the worst that could happen?

Not enough is known about that, believes an international group of researchers who, under the leadership of Cambridge University, have published the report “Climate Endgame: Exploring catastrophic climate change scenarios” in Proceedings of the National Academy of Sciences (PNAS) journal on Tuesday.

The report claims that there is too little research into the consequences of global mean temperature increases of 3 °C or more compared to milder temperature increases. The report refers to a review of the reports from the UN’s Intergovernmental Panel on Climate Change (IPCC), which points to a tendency to examine the consequences of lower temperature increases in the most depth. This is despite the fact that high temperature increases and associated extreme weather events are not unlikely.

But what could go wrong?

“There are plenty of reasons to believe climate change could become catastrophic, even at modest levels of warming,” lead author Luke Kemp from Cambridge’s Centre for the Study of Existential Risk says in a press release.

The report tries to unify existing knowledge about the consequences of a global mean temperature increase of 3 °C or more and juxtapose it with other risk factors that have the potential to make matters worse. Those could be, for example, political instability, risk of infectious diseases, and increased levels of conflict among countries with nuclear weapons, as shown on the map below.

A map comparing unstable countries with nuclear weapons, laboratories for infectious diseases, and areas in which annual mean temperature may exceed 29 degrees in the near future. Illustration: Cambridge University

The conclusion is that, in essence, not enough research has been done into the interaction between these risks and their extreme consequences, including the worst-case scenarios. Questions such as “What is the worst that can happen?”, “How likely is a societal collapse?”, and “Is there a risk of human extinction?” are under-examined, the group of researchers believes.

Luke Kemp does not consider it likely that humanity will perish in this century, but he believes that we should know the specific risks in order to prepare for climate change accordingly.

“Even if we have a 1% chance of having a global catastrophe, going extinct over the coming century, that 1%, that is way too high,” he said to the New Zealand media outlet NZ Herald.

An impossible calculation

Kirsten Halsnæs, climate researcher at DTU and co-author of two IPCC reports, agrees with the researchers that more research could be done into extreme climate events. However, she does not believe that research has reached the point where one could calculate the probability of the extinction of humanity.

“It’s quite far-fetched to say that there is a probability, because then you need to have a probability factor for all the elements that are included. This applies to both the climate models, all the economic consequences, and the consequences in nature. So it would be quite extensive work and it would require several years of research.”

Kirsten Halsnæs points out that it is difficult to assess the consequences of extreme events as we currently know too little about how and how often the extreme events will occur.

“There is constant discussion about whether the various temperature changes give rise to dangerous man-made climate changes in specific areas. I think that we need to work more with thorough scientific studies of the extreme climate events such as heat waves, storms, floods, and droughts.”

According to Halsnæs, we cannot be as sure of an impending climate disaster as the report suggests.

What should the seventh IPCC report contain?

In addition to a general appeal to climate researchers to do more research into the extreme conditions, the report also contains a call to the IPCC. The next major climate report should focus on the possible consequences of extreme temperature increases of three degrees or more, including the risk of the end of humanity, the authors believe. It would provide an opportunity to better inform the public and trigger further research, in the same way that previous reports from the IPCC have done.

According to Kirsten Halsnæs, however, it would be pointless if the literature, as mentioned, is lacking.

“After all, none of the IPCC reports, based on a review of existing research, have found a basis for the claim that climate change is an existential crisis for humanity.”

The authors suggest that climate scientists should in future investigate the risk of mass extinction events and which mechanisms could lead to many people dying in a short time. Here, one should pay particular attention to the four major threats that climate change could intensify: famine and malnutrition, extreme weather events, conflict, and vector-borne diseases.

It is also crucial to assess society’s resilience in the event of several crises and disasters striking at the same time. And finally, it should be investigated how all these factors can be integrated into a comprehensive disaster assessment, according to the international group of researchers.

Should we be the prophets of doom?

This is a heavy subject, and the prospect of potentially startling or gloomy conclusions may create more indifference than climate action. At least that is the widespread attitude towards climate alarmism, but the authors do not agree with it. In the report, they refer to sources that demonstrate that the effect on people and world leaders depends entirely on how the results are communicated:

“Effective communication of research results will be key. While there is concern that fear-invoking messages may be unhelpful and induce paralysis, the evidence on hopeful vs. fearful messaging is mixed, even across metaanalyses. The role of emotions is complex, and it is strategic to adjust messages for specific audiences.”

More knowledge about various future scenarios, including the worst-case ones, can help compel more concrete action among the world’s population and leaders, Luke Kemp believes.

“Understanding nuclear winter performed a similar function for debates over nuclear disarmament,” he points out. Even if it does not turn out that humanity is at risk of extinction, it would be a good idea to investigate just to be safe, Kemp believes:

“Facing a future of accelerating climate change while remaining blind to worst-case scenarios is naive risk-management at best and fatally foolish at worst.”