An international team of researchers led by the University of Cambridge said “catastrophic” scenarios could be caused by global warming worse than many have predicted, or by cascading effects of events – or both at the same time. As a result, they said the world should start preparing for the possibility of a “climate endgame” for our species. In order to fully assess the range of risks, the team has proposed a research agenda to address scenarios from bad to worst. 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 from the Cambridge Center for the Study of Existential Risk. “Climate change has played a role in every mass extinction event. Help fallen empires and shape history. Even the modern world seems adapted to a particular climatic niche,” he said. “Pathways to disaster are not limited to the immediate effects of high temperatures, such as extreme weather events. Shock effects such as economic crises, conflicts and new disease outbreaks could trigger other disasters and hinder recovery from potential disasters such as nuclear war.’ Dr Kemp and his colleagues said the consequences of warming at 3 degrees Celsius and beyond, and the associated extreme risks, have been under-researched. Modeling done by the team shows areas of extreme heat – an annual average temperature of more than 29C – could affect two billion people by 2070. These regions are not only some of the most densely populated but also some of the most politically fragile. “Average annual temperatures of 29 degrees are currently affecting about 30 million people in the Sahara and Gulf coasts,” said co-author Chi Xu of Nanjing University. Abandoned houses in Hong Kong. Scientists say we need to look more closely at worst-case to worst-case climate scenarios (Getty) “By 2070, these temperatures and the social and political consequences will directly affect two nuclear power plants and seven maximum containment laboratories that harbor the most dangerous pathogens. There is a serious potential for catastrophic effects,” he said. Last year’s IPCC report suggested that if atmospheric carbon dioxide doubles from pre-industrial levels – which the planet is halfway to – then there is about an 18 per cent chance that temperatures will rise by more than 4.5 degrees Celsius. The research team said current scientific methodology has a growing tendency to consider less dangerous future scenarios that require a smaller-scale response. Dr Kemp co-authored a “text mining” study of existing IPCC reports, published earlier this year, which found that IPCC assessments have moved away from high-level warming to increasingly focus on lower temperature increases. This builds on previous work he has done showing that extreme temperature scenarios are “overexplored relative to their likelihood”. “We know less about the scenarios that matter most,” Dr. Kemp said. The team has now proposed a research agenda that includes what it calls the “four horsemen” of the climate endgame. These are: hunger and malnutrition, extreme weather conditions, conflict and vector-borne diseases. Global food supplies face enormous risks from warmer climates, according to the group, with increasing chances of “breadbasket failure” as the world’s most agriculturally productive regions suffer a “collective collapse”. Warmer and more extreme weather could also create conditions for new disease outbreaks as habitats for both people and wildlife change and shrink. Experts also warned that environmental collapse would likely exacerbate other “interacting threats”. They highlighted rising levels of inequality, misinformation, the potential for democratic collapses and even new forms of destructive artificial intelligence (AI) weapons. One dystopian scenario considered in the paper is described as “hot wars” – in which technologically enhanced superpowers fight to reduce the carbon footprint, while also conducting giant experiments to divert sunlight and lower global temperatures. The team said more emphasis should be placed on identifying all the potential tipping points that could push us towards a “Greenhouse Earth”. These include methane released by melting permafrost resulting in 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 greater the cause for concern,” said co-author Professor Johan Rockström, director of the Potsdam Institute for Climate Impact Research. “We understand more and more that our planet is a more evolved and fragile organism. We have to do the math of disaster to avoid it,” he said. Dr Kemp added: “We know that warming has 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 foolish at worst.” The research is published in the journal Proceedings of the National Academy of Sciences.
