On August 31, the National Oceanic and Atmospheric Administration (NOAA) released the report State of the Climate in 2021, suggesting that climate change is accelerating, with concentrations of greenhouse gases (all carbon dioxide, methane, and nitrous oxide) in the atmosphere and sea level reaching record highs last year. Sea level has risen 9.7 cm since 1993, when satellite observations began, and the melting of the Greenland ice sheet is currently contributing the most to sea level rise. Other studies suggest that if the Greenland ice sheet continues to melt at the rate recorded between 2000 and 2019, sea level could rise 27 cm during this century.　

The Arctic Ocean is said to be warming faster than other regions, and the melting of the ice sheet could become a tipping point that modifies the atmospheric flow, leading to extreme weather events on a global scale. In fact, in Asia in August, record heat waves and droughts in southern China and flooding in Pakistan caused by monsoon rainfall that was nearly 10 times higher than normal and affected 33 million people have been pointed to climate change as the cause of these extreme weather events.　

A paper titled Climate Endgame: Exploring catastrophic climate change scenarios has been published in PNAS.The paper argues that while there is a lack of understanding about the potential for societal failure due to climate change, assuming bad-to-worst-case scenarios is necessary for prudent risk management.

The paper cites as evidence the impact of the "nuclear winter" debate of 1983 on public opinion toward denuclearization, and the consequences of the COVID-19 pandemic on the world without adequate preparedness.

The paper suggests that analysis of the mechanisms that cause extreme outcomes can help to motivate action, improve resilience, and shape policy, including emergency measures. This includes not only high temperature scenarios, but also an understanding of how systemic risks of climate change can cause a domino effect of various unforeseen events. The authors also mentioned that facing climate change without assuming worst-case scenarios is too naïve risk management, and pointed out the importance of effective communication to public opinion about the need for risk management that assumes worst-case scenarios.

Reference
Luke Kemp et al. Climate Endgame: Exploring catastrophic climate change scenarios. PNAS. 119 (34) e2108146119 https://doi.org/10.1073/pnas.2108146119

Contributor: IIYAMA Miyuki (Information Program)