Despite decades of warnings from the world’s top scientists that soaring greenhouse gas emissions bring the planet closer to catastrophe, the scale of the perils ahead remains “dangerously underexplored”, experts have warned. experts.
An international team of researchers led by the University of Cambridge said “catastrophic” scenarios could be triggered by worse global warming than many had predicted, or by cascading impacts of events – or both at the latest. time.
As a result, they said the world must begin to prepare for the possibility of a “climate endgame” for our species.
In order to fully assess the range of risks, the team proposed a research agenda to deal with worst-case scenarios.
These include results ranging from a loss of 10% of the world’s population to the complete extinction of humanity.
The researchers are calling on the UN’s Intergovernmental Panel on Climate Change (IPCC) to devote a future report to “catastrophic climate change”, which they hope will boost research and inform the public.
“There are many reasons to believe that climate change could become catastrophic, even at modest levels of warming,” said lead author Dr Luke Kemp, from the Cambridge Center for the Study of Existential Risk.
“Climate change has played a role in every mass extinction event. It helped bring down empires and shaped history. Even the modern world seems suited to a particular climatic niche,” he 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 further calamities and hamper recovery from potential disasters such as nuclear war.
Dr Kemp and his colleagues said the consequences of warming from 3C and beyond, and the associated extreme risks, have been under-examined.
Modeling carried out by the team shows that areas of extreme heat – an annual average temperature of over 29C – could affect two billion people by 2070.
These areas are not only among the most densely populated, but also among the most politically fragile.
“Average annual temperatures of 29 degrees currently affect around 30 million people in the Sahara and the 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 ripple effects,” he said.
Last year’s IPCC report suggested that if atmospheric carbon dioxide doubles from pre-industrial levels – which the planet is halfway through – then there’s about an 18% chance that temperatures will rise further. 4.5°C.
The research team said the current methodology of the scientific community increasingly tends to look at less risky future scenarios that require a smaller scale response.
Dr Kemp is co-author of a text mining study of existing IPCC reports, published earlier this year, which found that IPCC assessments have moved away from high-end warming to focus increasingly more on lower temperature rises.
This builds on previous work he has done showing that extreme temperature scenarios are “underexplored relative to their likelihood”.
“We know the least about the most important scenarios,” Dr Kemp said.
The team has now proposed a research agenda that includes what they call the “four horsemen” of climate endgame. These are: starvation and malnutrition, extreme weather conditions, conflict and vector-borne diseases.
According to the team, global food supplies face huge risks from warmer climates, with increasing probabilities of “breadcrumbs” as the world’s most agriculturally productive areas experience “collective collapses”. “.
Warmer and more extreme weather patterns could also create conditions for new outbreaks as habitats for people and wildlife shift and shrink.
Experts have also warned that environmental degradation is likely to exacerbate other “interactive threats”. They highlighted rising levels of inequality, misinformation, the potential for democratic collapse, and even new forms of destructive artificial intelligence (AI) weapons.
A dystopian scenario envisioned in the article is described as “hot wars” – in which technologically-enhanced superpowers fight for shrinking carbon space while conducting giant experiments to deflect sunlight and reduce global temperatures. .
The team said there needs to be more focus on identifying all the potential tipping points that could push us towards a “Toncher Earth”.
These include methane released by melting permafrost, 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 works, the more there is to worry about,” 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 calculate the disaster in order to avoid it,” he said.
Dr Kemp added: “We know that increasing temperature has a ‘fat tail’, meaning a wide range of lower probabilities but potentially extreme outcomes. Facing a future of accelerating climate change while remaining blind to worst-case scenarios is naïve risk management at best and fatally foolish at worst.
The research is published in the journal Proceedings of the National Academy of Sciences.