Graph of the Day: Increase in Total Annual Precipitation in the U.S. versus Storm Size, 1948-2011

This figure shows that the very largest storms are getting bigger, faster, than other storms. All storm categories are defined relative to the local climate at each weather station used in this analysis. For example, the far right column represents the change over time in the amount of total precipitation produced by the largest 0.1 percent of storm events at each weather station we used across the contiguous United States. The Largest Changes Appeared at the Extremes The trends toward more frequent and more intense rainstorms and snowstorms were even more pronounced and substantial for larger events. In other words, the most extreme storms are those that have experienced the greater increase in their likelihood. Focusing in the most extreme rainstorms and snowstorms—those in the upper 0.3 percent to 0.1 percent of precipitation events at any given weather station over the period of analysis—shows that the more unusual the storm, the faster the increase in total precipitation over time. From 1948 to 2011, the amount of total annual precipitation across the 3,700 weather stations scattered across the contiguous United States that were used for this analysis increased by about 9 percent. The amount of precipitation produced by the largest 5 percent of downpours at every weather station over the period of analysis increased by 27 percent. However, the amount of total annual precipitation produced by the largest 0.1 percent of downpours increased by more than 70 percent. This is consistent with trends noted by scientists at the U.S. Soil and Water Conservation Society and the U.S. National Climatic Data Center, with trends noted by the Rocky Mountain Climate Organization and the Natural Resources Defense Council, and consistent with anticipated future impacts of global warming.

When It Rains, It Pours: Global Warming and the Increase in Extreme Precipitation from 1948 to 2011