One of the most-cited effects of global warming is that of rising temperatures on crops – hotter average conditions should lead to warmer, drier conditions, reducing yields in the best growing areas and maybe eliminating them where conditions today are marginal. In this week’s Science, a new study puts some numbers behind that speculation [$-a], and the news is not good.
Photo by Josh Sommmers.
Assembling the results of 23 climate models, authors Battisti and Naylor compare projected temperature ranges for the coming century with the ranges observed in the previous one. By the final decade of the twenty-first century, they say, summertime high temperatures in most of the continental U.S. have a 70% probability of exceeding the hottest summer temperatures ever recorded; in Saharan Africa, much of the Middle East and central Asia, the probability is 90-100%.
To put these numbers into perspective, Battisti and Naylor go to the history books, citing an array of cases in which local high temperatures have disrupted food production, creating regional shortages that eventually impacted worldwide food markets:
By comparison, extremely high summer-averaged temperature in the former Soviet Union (USSR) in 1972 contributed to disruptions in world cereal markets and food security that remain a legacy in the minds of food policy analysts to this day. … Nominal prices for wheat — the crop most affected by the USSR weather shock — rose from $60 to $208 per metric ton in international markets between the first quarters of 1972 and 1974.
Battisti and Naylor end by calling for substantial investment in adaptation measures to prevent “a perpetual food crisis.” Increasingly, this looks like the only practical course of action – although reducing and eliminating man-made greenhouse gas emissions is critical, turning global climate around is going to be like steering an aircraft carrier, and it’s going to get pretty warm before we turn the corner.
D.S. Battisti, R.L. Naylor (2009). Historical warnings of future food insecurity with unprecedented seasonal heat Science, 323 (5911), 240-4 DOI: 10.1126/science.1164363