The Century of Drought

Back in October, the National Center for Atmospheric Research published a complete literature review, “Drought under global warming: a review,” (See NCAR analysis warns we risk multiple, devastating global droughts even on moderate emissions path). That study makes clear that Dust-Bowlification may be the impact of human-caused climate change that hits the most people by mid-century, as the figures below suggests (“a reading of -4 or below is considered extreme drought”):

The PDSI [Palmer Drought Severity Index] in the Great Plains during the Dust Bowl apparently spiked very briefly to -6, but otherwise rarely exceeded -3 for the decade.
The National Center for Atmospheric Research notes “By the end of the century, many populated areas, including parts of the United States, could face readings in the range of -8 to -10, and much of the Mediterranean could fall to -15 to -20. Such readings would be almost unprecedented.”. Fundamentally large parts of the planet could become practically uninhabitable.

Rapidly warming climate is likely to seriously alter crop yields in the tropics and subtropics by the end of this century and, without adaptation, will leave half the world’s population facing serious food shortages.
“The stresses on global food production from temperature alone are going to be huge, and that doesn’t take into account water supplies stressed by the higher temperatures,” said David Battisti, a University of Washington atmospheric sciences professor.

For the record, the NCAR study merely models the IPCC’s “moderate” A1B scenario — atmospheric concentrations of CO2 around 520 ppm in 2050 and 700 in 2100. We’re currently on the A1F1 pathway, which would takes us to 1000 ppm by century’s end, but I’m sure with an aggressive program of energy R&D we could keep that to, say 900 ppm.
The UK Met Office came to a similar view four years ago in their analysis, projecting severe drought over 40% of the Earth’s habited landmass by century’s end (see “The Century of Drought“).