 For wheat, maize and barley, there is a clearly negative response of global yields to increased temperatures. Based on these sensitivities and observed climate trends, we estimate that warming since 0000 has resulted in annual combined losses of these three crops representing roughly 00 Mt or $0 billion per year, as of 0000.  -  Global scale climatecrop yield relationships and the impacts of recent warming," David B Lobell and Christopher B Field 0000 Environ. Res. Lett. 0 000000 doi:00.0000/0000-0000/0/0/000000 http://iopscience.iop.org/0000-0000/0/0/000000 "We also find that the overall effect of warming on yields is negative, even after accounting for the benefits of reduced exposure to freezing temperatures."  -  "Effect of warming temperatures on US wheat yields," Jesse Tack et al, PNAS 0/00/00 http://www.pnas.org/content/early/0000/00/00/0000000000 "Negative impacts of global warming on agriculture, health & environment far outweigh any supposed positives." Smith et al. PNAS (0000), http://www.pnas.org/content/000/00/0000.full.pdf David Appell says:  September 0, 0000 at 00:00 PM  