Climate-Driven Food Crisis in Second Half of the Century

The statement in the title is a conclusion from a 2009 study in Science "Historical Warnings of Future Food Security with Unprecedented Seasonal Heat". The University of Washington news release explained that rapisly warming climate is likely to seriously alter crop yiealds in the tropics and subtropics by the end of this century and, without adaptation, will leave half of the worlds's population facing serious food shortages.
David Battisti said: "The stresses on global food production from temperature alone are going to be huge, and that doesen't take into account water supplies stressed by the higher temperatures."
Currently 3 billion people live in the tropics and subtropics, and their number is expected to nearly double by the end of the century. If we end up with 5.5 degrees C warming or more by the century's end, and if you throw in the desertification and sharps drops in soil moisture then simply developing crops that are tolerant to heat and heat-induced water stress along with better irrigation is likely to prove utterly inadequate and irrelevant for billions of people.
The only genuine hope for avoiding the worst form of triage is aggressive and immediate agreenhouse gas mitigation.