Global warming hits Cereal production hard
According to the first study on the impact of climate change on global food production from 1981 to 2002, fields of wheat, corn and barley throughout the world have produced a combined 40 million tonne less a year because of the increase in temperatures caused by human activities.

....”Most people tend to think of climate change as something that will impact the future, but this study shows that warming over the past two decades has already had real effects on the global food supply,” said Christopher Field, co-author of the study and director of Carnegie Institution's department of
global ecology.