Crop Yields and Climate Change to the Year 2000. Volume I. Report on the Second Phase of a Climate Impact Assessment

摘要

As previously reported, a broad spectrum of subjective probabilities was distilled into five scenarios which describe possible global climate changes to the year 2000. Reported herein are estimates of how crop yields would respond to these climate changes if there were no changes in agricultural technology. The most likely climate change, a slight global warming with a 'probability' of 0.30, was found to have negligible effects on 15 'key' crops. The more appreciable effects of the other climate changes differed from crop to crop in direction and magnitude; Canadian and Soviet wheat yields registered the largest responses. The potential crop-yield effects of technological change are judged to be severalfold larger than the effects of the posited climate changes. In the second phase of this study, a simple climate-response model was used to project frequency distributions of annual yields, absent technological change. The inputs for a particular crop and assumed climate change were (1) a joint distribution of annual temperature and precipitation, and (2) an expression for annual yield as a function of the same variables. The first input was derived from the climatological records of the crop region, the second from estimates made by an Agriculture Panel. The panelists also projected yield trends to 2000 AD in consideration of perceived changes in technology, but no change in climate. When aggregated, their projections imply yield increases of about 10% for Australian wheat and 50% for Argentine corn; the remainder of the expected technology-induced increases lie between 20% and 40%.