Post apocalyptic scene.
Global heating could become “catastrophic” for humanity if temperature rises are worse than many predict or cause consequences we have yet to consider. The world needs to start preparing for the bad-to-worst-case scenarios according to a study by an international team of researchers led by the University of Cambridge.
“There are plenty of reasons to believe climate change could become catastrophic, even at modest levels of warming,” said lead author Dr. Luke Kemp from Cambridge’s Center 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.”
Kemp and colleagues argue that the consequences of 3 degrees warming and beyond, and related extreme risks, have been under-examined.
Modeling done by the team shows areas of extreme heat (an annual average temperature of over 29 degrees Celsius), could cover two billion people by 2070. These areas not only some of the most densely populated, but also some of the most politically fragile.
“Average annual temperatures of 29 degrees currently affect around 30 million people in the Sahara and Gulf Coast,” said co-author Chi Xu of Nanjing University.
“By 2070, these temperatures and the social and political consequences will directly affect two nuclear powers, and seven maximum containment laboratories housing the most dangerous pathogens. There is serious potential for disastrous knock-on effects,” he said.
Last year’s Intergovernmental Panel on Climate Change report suggested that if atmospheric carbon dioxide doubles from pre-industrial levels—something the planet is halfway towards—then there is an roughly 18 percent chance temperatures will rise beyond the worst-case climate scenario of 4.5 degrees.
Rising temperatures pose a major threat to global food supply, the researchers say, with increasing probabilities of “breadbasket failures” as the world’s most agriculturally productive areas suffer heat waves and droughts.
Hotter and more extreme weather could also create conditions for new disease outbreaks as habitats for both people and wildlife shift and shrink, bringing animals hosting potentially dangerous pathogens in contact with humans.
The authors caution that climate breakdown would likely exacerbate other “interacting threats”: from rising inequality and misinformation to democratic breakdowns, wars and even new forms of destructive technology.
Suggested geoengineering experiments to combat climate change could have unforseen consequences. An “iron fertilization experiment” in 2020 to increase phytoplankton growth and carbon dioxide absorption of the ocean resulted in the opposite effect, causing algal blooms and a mass mortality.
More focus should go on identifying all potential tipping points within “Hothouse Earth” say the researchers: from methane released by permafrost melts to the loss of forests that act as carbon sinks, and even potential for vanishing cloud cover.
“The more we learn about how our planet functions, the greater the reason for concern,” said co-author Professor Johan Rockström, Director of the Potsdam Institute for Climate Impact Research.
“We increasingly understand that our planet is a more sophisticated and fragile organism. We must do the math of disaster in order to avoid it,” he said.
Co-author Professor Kristie Ebi from the University of Washington said: “We need an interdisciplinary endeavor to understand how climate change could trigger human mass morbidity and mortality.”
“We know that temperature rise has a ‘fat tail,” which means a wide range of lower probability but potentially extreme outcomes. 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,” concludes Kemp.
The open-access paper “Climate Endgame: Exploring catastrophic climate change scenarios” is published in Proceedings of the National Academy of Sciences (2022). Materials provided by University of Cambridge.
