Despite decades of warnings from the world’s top scientists that rising greenhouse gas emissions are driving the planet ever closer to catastrophe, the scale of the dangers ahead remains “dangerously understudied”, experts warn.
An international team of researchers led by the University of Cambridge said the “catastrophic” scenarios could be triggered by global warming that is worse than many have predicted, or by cascading effects of events – or both at the same time.
As a result, they said the world needs to start preparing for the possibility of a “climate endgame” for our species.
To fully assess the range of risks, the team proposed a research program to address worst-case to worst-case scenarios.
These include outcomes ranging from the loss of 10 percent of the world’s population to complete human extinction.
The researchers are calling on the UN’s Intergovernmental Panel on Climate Change (IPCC) to dedicate a future report to “catastrophic climate change”, which they hope will stimulate research and inform the public.
“There are many reasons to believe that climate change could become catastrophic, even at moderate levels of warming,” said lead author Dr Luke Kemp of the Cambridge Center for the Study of Existential Risk.
“Climate change has played a role in every mass extinction. It helped bring down empires and shaped history. Even the modern world seems adapted to a certain climatic niche,” he said.
“Pathways to disaster are not limited to the direct impacts of high temperatures, such as extreme weather events. Cascading effects such as financial crises, conflicts and new outbreaks of disease can trigger other disasters and hinder recovery from potential disasters such as nuclear war.
Dr Kemp and his colleagues said the consequences of 3C warming and beyond, and the associated extreme risks, had been understudied.
Modeling by the team shows that areas of extreme heat – an average annual temperature above 29C – could affect two billion people by 2070.
These areas are not only some of the most densely populated, but also some of the most politically vulnerable.
“Average annual temperatures of 29 degrees currently affect about 30 million people in the Sahara and the Gulf Coast,” said co-author Qi Xu of Nanjing University.
Abandoned houses in Hong Kong. Scientists say we need to look more closely at climate scenarios from bad to worst
(Getty)
“By 2070, these temperatures and the social and political consequences will directly affect two nuclear powers and seven maximum security laboratories storing the most dangerous pathogens. There is serious potential for catastrophic side effects,” he said.
Last year’s IPCC report suggested that if atmospheric carbon dioxide were to double from pre-industrial levels – something the planet is halfway towards – then there was roughly an 18 per cent chance of temperatures rising by more than 4.5C.
The research team said that the current methodology of the scientific community has a growing tendency to explore less risky future scenarios that require a response on a smaller scale.
Dr Kemp co-authored a ‘text mining’ study of existing IPCC reports published earlier this year, which found that the IPCC’s estimates had shifted away from high warming to an increasing focus on lower rises in the temperature.
This builds on previous work he has done showing that extreme temperature scenarios are “understudied relative to their likelihood”.
“We know the least about the scenarios that matter the most,” Dr. Kemp said.
The team has already proposed a research program involving what they call the “four horsemen” of the climate endgame. These are: hunger and malnutrition, extreme climatic conditions, conflict and vector-borne diseases.
Global food supplies face enormous risks from a hotter climate, the team says, with increasing likelihoods of “failures in the granary” as the world’s most productive agricultural areas suffer “collective collapses”.
Hotter and more extreme weather can also create the conditions for new disease outbreaks as habitats for both humans and wildlife shift and shrink.
Experts also warned that environmental collapse was likely to exacerbate other “interacting threats”. They highlighted rising levels of inequality, misinformation, the potential for democratic breakdowns and even new forms of destructive artificial intelligence (AI) weapons.
One dystopian scenario envisioned in the document is described as “warm wars” – in which technologically enhanced superpowers vie for dwindling carbon space while conducting giant experiments to deflect sunlight and lower global temperatures.
The team said they should focus more on identifying all the potential tipping points that could push us towards Greenhouse Earth.
These include the release of methane from melting permafrost to the loss of forests that act as “carbon sinks” and even the potential for cloud cover to disappear.
“The more we learn about how our planet functions, the greater the cause 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 complex and fragile organism. We have to do the math on the disaster to avoid it,” he said.
Dr Kemp added: “We know that temperature increases have a ‘fat tail’, meaning 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 stupid at worst.”
The research was published in the journal Proceedings of the National Academy of Sciences.
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