Climate change threats1-in-20 chance of warming causing catastrophic, or even existential, damage by 2050
A new study evaluating models of future climate scenarios has led to the creation of the new risk categories “catastrophic” and “unknown” to characterize the range of threats posed by rapid global warming. Researchers propose that unknown risks imply existential threats to the survival of humanity. The researchers identify a one-in-20 chance of temperature increase causing catastrophic damage or worse by 2050.
A new study evaluating models of future climate scenarios has led to the creation of the new risk categories “catastrophic” and “unknown” to characterize the range of threats posed by rapid global warming. Researchers propose that unknown risks imply existential threats to the survival of humanity.
These categories describe two low-probability but statistically significant scenarios that could play out by century’s end, in a new study by Veerabhadran Ramanathan, a distinguished professor of climate and atmospheric sciences at Scripps Institution of Oceanography at the University of California San Diego, and his former Scripps graduate student Yangyang Xu, now an assistant professor at Texas A&M University.
Scripps notes that the risk assessment stems from the objective stated in the 2015 Paris Agreement regarding climate change that society keep average global temperatures “well below” a 2°C (3.6°F) increase from what they were before the Industrial Revolution.
Even if that objective is met, a global temperature increase of 1.5°C (2.7°F) is still categorized as “dangerous,” meaning it could create substantial damage to human and natural systems. A temperature increase greater than 3°C (5.4°F) could lead to what the researchers term “catastrophic” effects, and an increase greater than 5°C (9°F) could lead to “unknown” consequences which they describe as beyond catastrophic including potentially existential threats. The specter of existential threats is raised to reflect the grave risks to human health and species extinction from warming beyond 5°C, which has not been experienced for at least the past 20 million years.
The scientists term warming probability of five percent or less as a “low-probability high-impact” scenario and assess such scenarios in the analysis. which appears today in the journal Proceedings of the National Academy of Sciences.
Ramanathan and Xu also describe three strategies for preventing the gravest threats from taking place.
“When we say 5 percent-probability high-impact event, people may dismiss it as small but it is equivalent to a one-in-20 chance the plane you are about to board will crash,” said Ramanathan. “We would never get on that plane with a one-in-20 chance of it coming down but we are willing to send our children and grandchildren on that plane.”
