18/08/2022 – Scenarios for a global temperature increase of more than 2 degrees have not been sufficiently studied. It is fatal, claim researchers in a study on the risks of the climate crisis. Humanity must prepare for catastrophic effects of high average temperatures. The interdisciplinary team of researchers, led by researchers from Cambridge, is making a difference. The consequences of moderate warming below 2 degrees are considered, as well as extreme scenarios of more than 4 degrees.
The climate crisis is unstoppable
Media reports and most recently the International Panel on Climate Change (IPCC) are often limited to the effects of the climate crisis with a global temperature increase of between 1.5 and 2 degrees Celsius. This corridor reflects the Paris climate goals, which the world has largely agreed upon.
According to the researchers, too little attention is paid to catastrophic consequences such as famine and malnutrition for large parts of humanity, the economic consequences of extreme weather conditions and possible pandemics, even in these moderate scenarios.
“Currently, about 30 million people in the Sahara and the Gulf Coast are affected by annual average temperatures of 29 degrees,” said Chi Xu of Nanjing University, co-author of the study. “By 2070, these temperatures and the social and political fallout will directly affect two nuclear powers and seven high-security laboratories housing the most dangerous pathogens. There is a serious potential for catastrophic consequences.” With around two billion people, the affected areas are among the most densely populated and politically most vulnerable.
Hardly explored hotearth scenarios
If all national climate commitments targeted for 2030 are met and fully implemented, by then CO2 emissions will lead to an average global warming of 2.4 degrees by 2100. This means that no country is likely to miss out its climate goals, no unexpected climate tipping points are likely to cause high levels of greenhouse gases, and temperature increases would actually end in the middle of what scientists think is likely.
A world with significantly higher temperatures is underexplored relative to its likelihood. According to the researchers, climate scenarios with more than 2 degrees of warming, but above all more than 3 degrees, have hardly been analyzed so far. Even in the ideal corridor mentioned above, temperatures can rise by up to 3 degrees. Scientists also refer to a future with a significantly higher average temperature as global warming scenarios.
The researchers argue that tipping points in warm-earth scenarios should be better investigated. These include exploding methane emissions from melting permafrost, the loss of forests that act as carbon sinks, and the potential disappearance of cloud cover.
On human extinction
Temperatures of more than 2 degrees above the pre-industrial average were last seen on Earth in the Pleistocene, about 2.6 million years ago. Humanity should prepare for a world of climate disasters, the scientists say. Although some disaster scenarios are unlikely, they are just so extreme that they cannot go unnoticed.
“We know the least about the scenarios that matter the most,” says Luke Kemp of the Cambridge Center for the Study of Existential Risk. The loss of 10 percent of the world’s population is as possible in such catastrophes as the extinction of humanity. “A better understanding of catastrophic climate scenarios can help compel the public to act. Understanding nuclear winter has served a similar function in debates about nuclear disarmament.” The research team has asked the IPCC to have extreme climate scenarios examined in a special report. jb