Global warming could become “catastrophic” for humanity if the rise in temperature is worse than many predict or if it triggers a cascade of events not yet considered, or both. “The world must start preparing for the possibility of a ‘climate endgame’.”
This is stated by an international team of researchers led by the University of Cambridge, which proposes an agenda to face the worst scenarios. These include outcomes ranging from the loss of 10% of the world’s population to eventual human extinction.
The article published in the journal PNAS asks the Intergovernmental Panel on Climate Change (IPCC) to dedicate a future report to catastrophic climate change to promote research and inform citizens.
“There are many reasons to believe that climate change can become catastrophic, even with modest levels of warming,” explains lead author Luke Kemp.
“This has played a role in all cases of mass extinction, has contributed to the fall of empires and has shaped history. Even the modern world seems to be adapted to a particular climatic niche,” he says.
“Pathways to disaster are not limited to direct impacts of high temperatures, such as extreme weather events. Knock-on effects, such as financial crises, conflicts, and new disease outbreaks, could trigger other calamities and impede recovery from potential catastrophes, such as nuclear war.”
Extreme heat will affect millions of people
Modeling carried out by the team shows that extreme heat zones (an average annual temperature of more than 29 degrees) could reach 2 billion people in 2070; These areas are not only some of the most densely populated, but also some of the most politically fragile.
“Annual average temperatures of 29 degrees currently affect about 30 million people in the Sahara and the Gulf Coast,” explains Chi Xu, from Nanjing University.
“In 2070, these temperatures and the social and political consequences will directly affect two nuclear powers and seven maximum containment laboratories that harbor the most dangerous pathogens. There is a high chance of disastrous side effects,” he says.
Last year’s IPCC report suggested that if atmospheric CO2 doubles from pre-industrial levels – something the planet is halfway towards – there is about an 18% chance that temperatures will rise beyond 4.5. degrees.
However, extreme temperature scenarios are “underexplored relative to their likelihood.”
The 4 horsemen of the end of the weather
The team behind the PNAS article proposes a research agenda that includes what they call the “four horsemen” of the end of climate: famine and malnutrition, extreme weather, conflict, and vector-borne diseases.
Rising temperatures pose a major threat to the global food supply and could set the stage for new disease outbreaks as the habitats of people and wildlife change and shrink.
For scientist Kristie Ebi, from the University of Washington, “we need an interdisciplinary effort to understand how climate change could trigger mass morbidity and mortality in humans.”
Furthermore, climate breakdown would likely exacerbate other threats: from rising inequality and misinformation to democratic collapse and even new forms of destructive artificial intelligence arsenal.
Lluís Brotons, CSIC researcher at the Center for Ecological Research and Forestry Applications (CREAF), Spain, points out that the study “puts its finger on the sore spot of realism and a sense of precaution”.
“It raises the need for us to evaluate the implications of this type of scenario in a much more serious way than we have done so far, for example, through a specific evaluation of the IPCC,” adds the scientist to Science Media Center Spain, who does not participate in the study.
