Global Warming And Drought

Brad Plumer:

4) And future global warming will seriously dry out the United States. Keep in mind that human activity has only warmed the planet about 0.8°C above pre-industrial levels. According to the International Energy Agency, we’re on pace to warm the planet by 6°C by the end of the century. That’s a big difference. And plenty of scientific evidence suggests that warming will dramatically increase droughts around the world, including in North America.
This 2011 review paper (pdf) by Aiguo Dai of the National Center for Atmospheric Research summarizes much of what’s known about climate change and drought. In North America and around the world, decreased precipitation and increased evaporation will continue drying out soils and make persistent, Dust Bowl-style droughts more likely in the next 20 to 50 years. (Again, these droughts aren’t unprecedented, but they’re expected to become more frequent.) Here’s a map of what the world will look like mid-century under a “moderate” emissions scenario:

The Palmer Drought Severity Index mid-century under a moderate emissions scenario. Under the PDSI, "a reading of -4 or below is considered extreme drought." (Source: National Center for Atmospheric Research.)

That’s the expected Palmer Drought Severity Index around the world under a “moderate” warming scenario. Take a look at the United States, where the PDSI ranges from -4 to -8 in the Plains. As Joe Romm notes, the PDSI briefly spiked to -6 in the Plains during the Dust Bowl, but it rarely exceeded -3 for the rest of the 1930s. In other words, we can expect drought conditions more severe than they were during the Dust Bowl.

If this is even close to correct, we are very screwed.  As the story said in another part, droughts have been a part of our life forever, but they will probably become more likely with climate change.  Is that a big  risk to be taking?  Yes, it is. Is Midwestern farmland a good long-term investment at current prices?  I have no idea.  Anyway, this year may be warping our perspectives, but the chance of major change is very scary.