Read the full story at FiveThirtyEight.
Minnesota is getting wetter. Over the last 100 years, the state has seen more storms that produce heavy rainfall, and its strongest storms have grown more intense. One of the more dramatic changes is the increasing number of “mega-rain” events — rainstorms during which at least 6 inches of rain falls over at least 1,000 square miles and the center of the storm drops more than 8 inches of rain. Minnesota has had 11 mega-rains since 1973,1 and eight of them have come since 2000. Two mega-rains swept through in 2016, which is only the third time the state experienced more than one mega-rain in a year. (It also happened in 1975 and 2002.)
Experts suspect climate change is behind this and other shifts in precipitation patterns. But knowing what’s causing an increase in precipitation and knowing what to do about it are two different issues. Minnesota and states across the Midwest are confronting an uncertain, flood-prone future, one where changes in precipitation patterns could get even more dramatic. The precipitation estimates that city planners have relied on in making preparations for flooding are based on historical weather trends, not predictions of future trends, and the estimates themselves were sometimes decades old. New estimates have been released for Minnesota, but they only show how much has already changed. They have nothing to say about what change is coming next.