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The climate of the Great Plains of the United States and Canada has presented a challenge to agrarians throughout the centuries. In this paper I discuss some of the major climatological hazards to agriculture in the plains and some of the technological defenses that North Americans have so far used to adapt to adverse weather and climate. I conclude with a consideration of the implications for Great Plains agriculture of a likely man-induced (or anthropogenic) climatic change following the expected further increase of carbon dioxide in the atmosphere. For the purposes of this paper, I have defined agricultural drought as a climatic excursion involving a shortage of precipitation sufficient adversely to affect crop production or range production (Rosenberg 1980). Agricultural land can only be productive when there is a balance between moisture supplied to the land by precipitation or irrigation and that withdrawn by evaporation from the soil or transpiration through plants (together called evapotranspiration). Drought, of course, affects not only water supply, but because of drier air and reduced cloudiness increases the rate of water consumption, while water is yet available to be withdrawn.