Climate Change and Food Security
Global Warming and Agriculture: Impact Estimates by Country, W. Cline 2007

The 2007 Cline food security assessment was based on a global temperature increase of 3.3
ºC. We are currently on track for a 3ºC rise by 2050. We are looking at the world that today's children will see.

The climate models used in Cline's study predicted that under the IPCC's scenario A2 scenario  (high scenario as the world is on), that global mean temperature would rise by 3.3ºC.

Because of the uncertainty of the potential carbon fertilization benefits to some crops in some regions, Cline gave results for crop yield changes with and without fertilization benefits.

Risk management demands that changes without fertilization would be the basis of food security assessment, but instead the IPCC assessment based on the assumption of large CO2 fertilization benefits based on crop experiments of doubtful validity in the real world. 

W. Cline Assessment 2007.
Land areas would warm more than oceans, with the average surface temperature increasing by 5.0ºC weighting by land area and 4.4ºC weighting by farming area.

By the 2080s, global agricultural productivity would decline by about 3% with carbon fertilization effect and by about 16% if the carbon fertilization effect did not materialize.

These losses would be disproportionately concentrated in developing countries, which would suffer losses of 9% with carbon fertilization effect and 21% without carbon fertilization effect, in contrast to an 8% gain (with carbon fertilization effect) and 6% loss (without carbon fertilization effect) in industrial countries.
The detailed estimates by country and region reported in Table 1 indicate that South Asia and Africa would be the two regions most harmed by climate change. In Southeast Asia, the damages of climate change to agriculture would also be severe, ranking from 15.1% for Vietnam to 26.2% for Thailand if carbon fertilization effect did not materialize.