Scientists agree that changes in land use such as deforestation, and not just greenhouse gas emissions, can play a significant role altering the world’s climate systems. Now, a new study by researchers at MIT and Dartmouth College reveals how another type of land use, intensive agriculture, can impact regional climate.
The researchers show that in the last half of the 20th century, the midwestern U.S. went through an intensification of agricultural practices that led to dramatic increases in production of corn and soybeans. And, over the same period in that region, summers were significantly cooler and had greater rainfall than during the previous half-century. This effect, with regional cooling in a time of overall global warming, may have masked part of the warming effect that would have occurred over that period, and the new finding could help to refine global climate models by incorporating such regional effects.
The findings are being published this week in Geophysical Research Letters, in a paper by Ross Alter, a recent MIT postdoc; Elfatih Eltahir, the Breene M. Kerr Professor of Hydrology and Climate; and two others.
The team showed that there was a strong correlation, in both space and time, between the intensification of agriculture in the Midwest, the decrease in observed average daytime temperatures in the summer, and an increase in the observed local rainfall. In addition to this circumstantial evidence, they identified a mechanism that explains the association, suggesting that there was indeed a cause-and-effect link between the changes in vegetation and the climatic effects.
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