. 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 David Appell says:  September 0, 0000 at 0:00 PM  "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 mpainter says:  September 0, 0000 at 0:00 PM  Your studies were conducted under drought conditions and attributed yield decline to higher temperature instead of low soil moisture.