NCPA - National Center for Policy Analysis


May 19, 2005

Environmental lobbyists argue that continuing human-caused global warming poses a significant threat of world famine. They say hotter temperatures will cause crops to wither on the vine and increase the evaporation rate of moisture from the soil. The available evidence, however, undermines their claims, say Dennis T. Avery (Hudson Institute) and H. Sterling Burnett (National Center for Policy Analysis).

Indeed, a warmer planet has beneficial effects on food production. It results in longer growing seasons -- more sunshine and rainfall -- while summertime high temperatures change little. And a warmer planet means milder winters and fewer crop-killing frosts.

Botanists have long realized that CO2 enhances plant growth, which is why greenhouse owners pump large volumes of CO2 into their sheds -- to grow more tomatoes or carnations. This was confirmed by 55 experiments conducted by research scientist Sherwood Idso, formerly of the U.S. Department of Agriculture. For example:

  • Increasing CO2 by 300 parts per million (ppm) above the current atmospheric level of more than 370 ppm enhanced plant growth by 31 percent under optimal water conditions, and 63 percent under water scarcity.
  • With a 600 ppm CO2 increase, plant growth was enhanced 51 percent under optimal water conditions and an astonishing 219 percent under conditions of water shortage.

Based on nearly 800 scientific observations around the world, a doubling of CO2 from present levels would improve plant productivity on average by 32 percent across species. Controlled experiments have shown that:

  • Under elevated CO2 levels, average yields of cereal grains -- including rice, wheat, barley, oats and rye -- are 25 percent to 64 percent higher.
  • Tubers and root crops, including potatoes, yams and cassava, yield 18 to 75 percent more.
  • And yields of legumes, including peas, beans and soybeans, increase 28 to 46 percent.

Source: Dennis T. Avery and H. Sterling Burnett, "Global Warming: Famine -- or Feast?" National Center for Policy Analysis, Brief Analysis No. 517, May 19, 2005.

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