Summer Temperatures for Second Half Of Century Projected to Exceed Current Records, Contribute to Food Insecurity
by Jack Rosebro
A report published this week in Science compares the effects of two significant heat-induced disruptions of food production from recent history with projected effects of temperature increases up to and including the latter half of this century. The study finds that there is a greater than 90% likelihood that by 2080-2100, growing season temperatures will exceed even the most extreme seasonal temperatures recorded in the last century for the majority of the world’s tropics and subtropics, exposing an area with a current population of more than three billion people to food insecurity.
David Battisti of the University of Washington and Rosamond Naylor of Stanford University compared two historically significant examples of severe heat-induced crop decline—France in 2003 and the Ukraine in 1972—to average temperatures for more than a century. They found that climatological daily high temperatures from June to August were approximately 2-4 ºC higher in France and 3-5 ºC higher in the Ukraine than each region’s 1900-2006 average for those months. They then extrapolated the historical effects of the two events onto 23 climate models for the remainder of the 21st century.
European Grain Production and the Heat Wave of 2003
Record daytime and nighttime temperatures throughout the 2003 summer growing season in parts of Western Europe caused many crops to develop prematurely, entering into grain filling stages during insufficient soil moisture conditions. EU-15 maize and fodder production fell by 20%, with fodder production reduced by 60% in France alone. Fruit harvests were reduced by a quarter, and wheat harvests in France declined by more than 20% even though wheat had almost completely matured prior to the upswing in temperatures. Agricultural water consumption also rose significantly. Approximately 35,000 Europeans died from heat stress in 2003, with just under 15,000 dying in France during a three-week period.
The extreme temperatures of 2003 also disrupted energy systems in France. In some regions, river water levels dropped so low that nuclear reactors, which use river flows for cooling, had to be shut down, while six others-Saint-Alban (Isère), Golfech (Tarn-et-Garonne), Cruas (Ardèche), Nogent-sur-Seine (Aube), Tricastin (Drôme), and Bugey (Ain)-were unable to maintain cooling water discharge temperatures below legal limits.
Glaciers in the European Alps lost an average of about 3 meters water equivalent, which was almost twice as much as during the previous record year of 1998 and roughly five times more than the average loss of 0.65 meters per year recorded during the exceptionally warm period of 1980 to 2000. The global financial impact of summer 2003 heat, drought, and forest fires in France, Italy, Germany, Spain, Portugal, Austria, Hungary, Estonia and Slovakia has been estimated at €13.1 billion (US$17.6 billion).
Ukrainian Wheat Production and the Drought of 1972
The Ukraine wheat crisis of 1972, a product of low winter snow levels and temperatures coupled with summer drought and high temperatures, triggered disruptions in the world cereal market and a tripling of wheat prices during an otherwise steady half-century decline in prices following the Second World War. A 1976 review of the Ukranian food crisis noted that “it is also noteworthy that, on occasion, poor conditions for food production occur concomitantly at several places over the globe.” Drought in the Sahel and El Niño conditions off Peru impacted food production in those regions in 1972.
High temperatures and low precipitation also cut Ukrainian wheat production by 70% in 2003 and effectively cancelled most of its wheat exports for the year. According to the USDA, weather continues to be the “chief determinant” in Ukraine wheat yields, which recently declined for three years running before rebounding in 2008.
In both cases studied by Battisti and Naylor, observed heat-induced declines in food production were found to be consistent with crop model results reviewed in last year’s US Department of Agriculture (USDA) report The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity. (Earlier post.) That report, which drew on research from the National Center for Atmospheric Research (NCAR) and the University Corporation for Atmospheric Research (UCAR) as well as USDA, concluded that even under the most optimistic CO2 emission scenarios, North American ecosystems “are likely to be pushed increasingly into alternate states with the possible breakdown of traditional species relationships, such as pollinator/plant and predator/prey interactions, adding additional stresses and potential for system failures.”
The USDA report further noted that while some agricultural and forest systems may experience short-term increases in productivity, “many such systems are likely to experience overall decreases in productivity that could result in economic losses, diminished ecosystem services, and the need for new, and in many cases significant, changes to management regimes” over the long term.
Battisti and Naylor also make mention of the Sahel, a semiarid and agriculturally precarious belt of land spanning Africa between the Sahara and the savannah belt below it, noting that “new bounds of heat stress will make the region’s population far more vulnerable to poverty and hunger-related deaths, and will likely drive many people out of agriculture altogether, thus expanding migrant and refugee populations.” A report last year by EU foreign policy chief Javier Solana Madariaga (earlier post) found that climate change could become a “threat multiplier” to European security and migration policy, with increasing drought, water scarcity and land overuse in North Africa and the Sahel leading to a loss of three-quarters of arable, rain-fed land, and resulting in significant migration.
Historical regional food shortages in France, the Ukraine, and the Sahel were offset by the availability of food from surrounding regions as well as the eventual subsiding of unusual temperatures. “The future, however, could be entirely different,” write the researchers.
If growing season temperatures by the end of the twenty-first century remain chronically high and greatly exceed the hottest temperature on record throughout the much of the world, not just for these three examples, then global food security will be severely jeopardized unless large adaptation investments are made.
History provides some guide to the magnitude and effects of high seasonal averaged temperature projected for the future. Ignoring climate projections at this stage will only result in the worst form of triage.—Battisti and Naylor (2009)
 David S. Battisti and Rosamond L. Naylor, Historical warnings of future food insecurity with unprecedented seasonal heat. In Science,volume 323, number 5911, 9 January 2009
 COPA-COGECA: Assessment of the impact of the heat wave and drought of the summer 2003 on agriculture and forestry. September 2003
 P. Pirard et al.: Summary of the mortality impact assessment of the 2003 heat wave in France. Eurosurveillance, 1 July 2005
 A. De Bono, et al.: Impacts of summer 2003 heat wave in Europe. United Nations Environment Programme, March 2004
 Reginald E. Newell, Minoru Tanaka, and Bijoy Misra, Department of Meteorology, Massachusetts Institute of Technology: Climate and Food Workshop: A Report. Bulletin of the American Meteorological Society, Volume 57, No. 2, February 1976
 Peter Backlund et al.: The effects of climate change on agriculture, land resources, water resources, and biodiversity in the United States. US Department of Agriculture, May 2008
 Javier Solana: Climate change and international security. Council of the European Union, 3 March 2008.