Episode Details

Climate change is increasing flood risk worldwide.  

Climate change is intensifying flood risk around the world, with potentially devastating consequences for communities and infrastructure.  As the planet gets hotter, the atmosphere's capacity to hold water vapor increases, leading to more frequent and intense precipitation events in certain regions.  Extreme rainfall events can overwhelm stormwater and other drainage systems and result in dangerous flash flooding. A 2021 study published by the American Meteorological Society found that for every 1°C rise in global temperature, the intensity of extreme rainfall events increases by 7 percent.  Sea level rise, driven by melting glaciers, is also causing coastal flooding and erosion in many parts of the world.  Sea levels could rise by an average of 10 - 12 inches in the U.S. in the next 30 years (2020 – 2050)—as much as the rise measured over the last 100 years (1920 - 2020).  By the end of the century, sea levels could be as much as 3.6 feet higher than they are today, putting nearly 200 million people at risk.   

These changes are already having real-world consequences. In 2021, severe flooding in Germany, Belgium, the Netherlands, and other European countries killed over 200 people and destroyed entire towns.  In the United States, severe coastal flooding from Superstorm Sandy was partially caused by unusually high storm surges attributed to sea level rise.  

While these challenges may be daunting, there are concrete actions we can take now to increase our resilience, such as greater investment in flood control infrastructure and natural interventions to mitigate flood risk.  These and other solutions are discussed in more detail below.   

A recent study indicates that climate change is increasing the risk of a “megaflood” in California.

California has experienced great floods every century or so for many millennia, according to historical and climate records. The last great flood in California was in 1862, which inundated a 300-mile-long stretch of the Central Valley, including highly populated areas such as Sacramento.  The “Great Flood of 1862” is widely considered the benchmark for a “plausible worst-case scenario” flood in contemporary California. 

Recent research suggests that climate change has already increased the risk of extreme floods in California, and that it is likely to significantly increase the risk of even more extreme floods in the future. A 2022 study by UCLA climate scientist Daniel Swain and fellow researcher Xingying Huang found that despite the recent prevalence of severe drought, California faces a broadly underappreciated risk of severe floods. The study indicates that climate change has already doubled the risk of a present-day megastorm, relative to a century ago, and more than tripled the risk of a trillion-dollar megaflood like the Great Flood of 1862.  It further found that larger future increases are likely