Surging floodwaters in Guerneville, California. Record snowfall from Eau Claire, Wisconsin to Flagstaff, Arizona. Mudslides in Tennessee and North Carolina. The past month has been full of extreme precipitation, making it the wettest winter on record for the contiguous U.S.
Heavy rain is a hallmark of climate change. A 1°F increase leads to 4 percent more water vapor in the atmosphere, strengthening downpours. As the NOAA/NCEI Climate Extremes Index indicates, the 10 years with the most extreme 1-day precipitation have all come since 1995.
The trend is part of a broader increase in extreme events. The NOAA/NCEI Climate Extremes Index evaluates the percentage of the contiguous U.S. that is much above (or below) normal for six indicators related to temperature, drought, precipitation, and tropical cyclones (includes full range of organized tropical systems). Even though the data goes back to 1910, four of the top five values occurred in 2012, 2015, 2016, and 2017 (2018 was eighth). Among these different climate extremes, water imbalance issues stand out. As we reported last month, the projected climate impact of highest risk for two thirds of the country is extreme precipitation, drought, or water scarcity.