Despite decades of warnings from the best scientists in the world that rising greenhouse gas emissions are bringing the planet ever closer to catastrophe, the magnitude of the dangers ahead remain “dangerously underexplored,” experts warn.
An international team of researchers led by the University of Cambridge said “catastrophic” scenarios could be triggered by worse global warming than many have predicted, or by cascading impacts of events – or both simultaneously.
As a result, they said the world must start preparing for the possibility of a “climate game end” for our species.
In order to fully assess the range of risks, the team proposed a research agenda to address worst-case scenarios.
These include results ranging from the loss of 10% of the world population to complete human extinction.
The researchers are calling on the United Nations Intergovernmental Panel on Climate Change (IPCC) to dedicate a future report to “catastrophic climate change,” which they hope will galvanize research and inform the public.
“There are many reasons to believe that climate change can become catastrophic, even at modest warming levels,” said lead author Dr. Luke Kemp of the Center for the Study of Existential Risk in Cambridge.
“Climate change has played a role in every mass extinction event. It aided the fall of empires and shaped history. The modern world also seems adapted to a particular climate niche, ”she said.
“The paths to disaster are not limited to the direct impacts of high temperatures, such as extreme weather events. Ripple effects such as financial crises, conflicts and new epidemics could trigger other calamities and prevent recovery from potential disasters such as nuclear war. “
Dr Kemp and his colleagues said the consequences of warming 3 ° C and above, and the associated extreme risks, have been underestimated.
Models made by the team show that areas of extreme heat – an average annual temperature of over 29 ° C – 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 fragile.
“Average annual temperatures of 29 degrees currently affect about 30 million people in the Sahara and the Gulf coast,” said co-author Chi Xu of the University of Nanjing.
By 2070, these temperatures and the social and political consequences will directly affect two nuclear powers and seven maximum containment laboratories that house the most dangerous pathogens. There is serious potential for disastrous ripple effects, “she said.
Last year’s IPCC report suggested that if atmospheric carbon dioxide doubles from pre-industrial levels – something the planet is halfway to – then there is a roughly 18% chance that temperatures will rise by more than 4.5 ° C.
The research team said that the scientific community’s current methodology has a growing tendency to examine less risky future scenarios that require a small-scale response.
Dr. Kemp co-authored a “text mining” study of existing IPCC reports, published earlier this year, which found that IPCC ratings have shifted from high-end warming to focus. more and more on the lower temperature rises.
This builds on previous work he has done showing that extreme temperature scenarios are “under-explored relative to their likelihood”.
“We know less about the scenarios that matter most,” said Dr. Kemp.
The team has now proposed a research agenda that includes what they call the “four horsemen” of the end of the climate game. These are: famine and malnutrition, extreme weather conditions, conflicts and vector-borne diseases.
According to the team, global food supplies face enormous risks from warmer climates, with increasing likelihood of ‘bread basket failures’ as the world’s most agriculturally productive areas experience ‘collective collapses’.
A warmer, more extreme climate could also create conditions for new outbreaks as habitats for both people and wildlife shift and shrink.
Experts also warned that environmental collapse is likely to exacerbate other “interacting threats”. They highlighted increasing levels of inequality, disinformation, the potential for democratic breakdowns, and even new forms of destructive artificial intelligence (AI) weapons.
A dystopian scenario envisioned in the document is described as “hot wars” – in which technologically advanced superpowers fight for the decrease in carbon space while also conducting giant experiments to deflect sunlight and reduce global temperatures.
The team said there is a need to focus more on identifying all potential tipping points that could push us towards a ‘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 extinction of cloud cover.
‘The more we learn about how our planet works, 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 sophisticated and fragile organism. We have to deal with the disaster to avoid it, “she said.
Dr Kemp added: “We know that rising temperature has a ‘fat tail’, which means a wide range of lower probabilities but potentially extreme results. Tackling a future of accelerating climate change while remaining blind to worst-case scenarios is naive risk management at best and fatally foolish at worst ”.
The research is published in the journal Proceedings of the National Academy of Sciences.