Chapter 60 Past Climate Change Impacts on Agriculture This paper examines the likely impact on agriculture of the climate change which has already taken place between 1960 and 2000. Accumulating greenhouse gases have caused global temperatures to rise approximately 0.25 °C during this period and for precipitation patterns to shift. Using cross sectional and crop simulation evidence temperature precipitation and carbon dioxide response functions are used to calculate the impacts on agriculture. Temperature and precipitation changes together have caused estimated global impacts ranging from a loss of 0.05% to a gain of 0.9% of agricultural GDP. Including carbon fertilization effects historic climate change is estimated to have caused a 2–4% increase in global production. Given the rapid increase in agricultural production over the last 40 years the contribution of climate change to the overall growth of agriculture has been small contributing between 2.6% and 5.4% of overall growth. This effect has been larger in mid to high latitude countries where climate change is estimated to have caused 4–7% of historic agricultural growth and smaller in low latitude countries where the climate change has contributed between 0.6% and 3% of the growth. Future climate changes which are expected to be much larger may well have very different effects than past climate changes. Future changes may continue to be slightly beneficial to global agriculture up to about 2.5 °C but they will eventually become harmful and cause reductions in global production.