Runaway climate risks in a warming world

A series of extreme weather events of unprecedented severity affected millions of people in 2021 and caused tremendous economic damage, including numerous casualties and incalculable human suffering. As the sixth warmest year on record so far (the first five hottest years on record all occurred after 2015), 2021 featured 18 “billion-dollar” climate-related events in the period of January to September alone in the U.S., with a total estimated damage of $104.8 billion.

This is the third-highest value for this time in year on record with Hurricane Ida which led to widespread flooding from Louisiana and to the Northeast including New York estimated as the costliest single disaster (more than $60 billion).

Globally, severe floods from extreme rainfall devastated cities in Central Europe, China and Turkey, while extreme heat occurred in India, the Mediterranean, Siberia and Northern Africa. For the first time, the UK Met office issued an extreme heat warning.

Not only the number but also the extent by which some of the recent weather extremes broke prior records was extraordinary. The Pacific Northwest heatwave of late June and early July broke prior records by double digits — and would have been virtually impossible in a pre- industrial climate. The rainfall extremes that flooded Central Europe and killed 200 people in Germany alone and provided more than a month’s worth of rain within 24 hours in some regions and was estimated as once in “500 years” event.

Even under given climatic conditions such events are thought of as very rare events. The recent cluster of these very extreme events might suggest that climate models tend to underestimate their frequency. While climate models have been very accurate in projecting future mean warming, extreme weather events often involve complex interactions of several physical variables on different spatial and temporal scales and are therefore more challenging. Therefore, projections of future extreme weather frequency and magnitude should be considered conservative estimates. 

In addition, climate extremes decreasingly act in isolation. A global increase in weather extremes exceedingly leads to situations in which several extremes interact e.g. through their spatial or temporal vicinity or joint effects on global supply chains. This can strongly amplify their impacts, far beyond the hypothesized sum of each disaster occurring in isolation. Such complex interactions make them difficult to predict, prepare for and manage in particular because capacities for disaster response are naturally limited, and needs are generally measured by past, historical events.

Concurrent extremes can push societies beyond the limits of adequate disaster response. Imagine a situation of simultaneous wildfires. Often, states provide assistance when support is needed, but who can help when everybody is struggling with their own fires. One wildfire might be easily controlled, but which fire do you put out first when several occur simultaneously and who will make these climate-triage decisions?

A series of consecutive weather extremes can severely slow down and at times inhibit recovery. Extremes often have long-lasting effects on human wellbeing, the economy and the resilience to future extremes with strong gradients between the global North and South. An increase in the frequency of weather extremes makes consecutive disasters more likely, at times preventing full recovery. This can permanently lower the quality of life in affected regions, making retreat the last option at times. The average time between billion-dollar disasters in the United States dropped from 82 days to 18 days comparing the 80s with the past five years.

“There is no glory in prevention” was a bon mot often repeated at the beginning of the COVID-19 pandemic, when severe lockdown decisions had to be justified as pre-emptive measures to avoid a breakdown of the health sector. There is no glory in seeing predictions becoming a reality either. Climate scientists have warned of catastrophic weather extremes as a result of unmitigated greenhouse gas emissions for decades.

Misinformation campaigns from the fossil fuel industry, however, have managed to delay action, through denial of the existence, relevance and human contribution of climate change and by pushing misleading narratives of individual guilt, diverting the focus from necessary systemic changes. Since the 2015 Paris Agreement was passed, CO2 emissions have continued to increase — reaching their highest values in 4 million years.

It seems as if climate science is heading toward a “tragic triumph” — being scientifically right but being ignored when it actually counts — without any notable effect on the steady rise of global emissions.

The tendency of climate models to underestimate extreme weather events and the complicated dynamics by which they can affect societies are a reminder that the 1.5-degree Celsius guardrail agreed upon by the international community in the Paris Agreement does not leave room for further delay. 

With the UN’s climate conference COP26 around the corner, states need to build back trust in the international climate negotiation process by quick and effective actions to limit global emissions. A further increase in climate extremes whose impacts are becoming more and more harmful and increasingly difficult to manage must be avoided.

Kai Kornhuber, Ph.D., is a climate scientist at the Earth Institute at  Columbia University, investigating statistics, physical mechanisms and societal risks connected to extreme weather events under current climates and future emission scenarios. Follow Kornhuber on Twitter: @kkornhuber

This piece has been updated.