A recent study by Brown University scientists suggests that impacts of climate change on agriculture might be worse than expected.  You can read about the study at https://news.brown.edu/articles/2016/03/matogrosso.

The scientists used satellite analysis of land use changes and studied cropping patterns in the Brazilian state of Mato Grosso.  They showed that an increase in average temperature in Mato Grosso of just 1 degree Celsius would lead to a nine to 13 percent reduction in overall production of soy and corn, due to both changes in yield and reduction in acreage in production due to decreased profitability.  Looking just at changes in yield does not give a full picture of the changes that are likely to occur and could cause an underestimate in the decrease in agricultural output.

The results are not entirely applicable to the US since risk reduction factors like crop insurance are less available there, but the study does reflect what could happen in many third-world countries trying to feed growing populations.  Climate Progress has some more discussion of the impacts on US farmers here.

Satellite mapping helps researchers see changes in crop area and double cropping. Analyses show that climate shocks are important drivers of the expansions and contractions seen here, suggesting a large and previously overlooked negative impact of climate change on food production. Dark purple indicates areas where double cropping has been abandoned. Light blue indicates areas where single cropping has been abandoned. NASA/Stephanie Spera/Brown University
Satellite mapping helps researchers see changes in crop area and double cropping. Analyses show that climate shocks are important drivers of the expansions and contractions seen here, suggesting a large and previously overlooked negative impact of climate change on food production. Dark purple indicates areas where double cropping has been abandoned. Light blue indicates areas where single cropping has been abandoned.
NASA/Stephanie Spera/Brown University