My posts concerning climate change so fare have described various feedback loops associated with our modern-day modification of the chemistry of the atmosphere.
There are predicted effects of global warming and there are demonstrated effects.
In February 2013 the U. S. Department of Agriculture released Technical Bulletin 1935 titled Climate Change and Agriculture in the United States: Effects and Adaptation.
The report's 56 authors represent USCA, UCAR (University Corporation for Atmospheric Research), and NCAR (National Center for Atmospheric Research).
The "Key Messages" from the Executive Summary are shown below.
Key Messages from USDA Technical Bulletin 1935, "Climate Change and Agriculture in the United States: Effects and Adaptation."