Author
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Howell, Terry |
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Submitted to: Proceedings of the Central Plains Irrigation Conference
Publication Type: Proceedings Publication Acceptance Date: 2/17/2009 Publication Date: 2/24/2009 Citation: Howell, T.A. 2009. Global climatic change effects on irrigation requirements for the Central Great Plains.In: Proceedings of the Central Plains Irrigation Conference and Exposition, February 24-25 2009, Colby, Kansas. p. 25-39. Interpretive Summary: Carbon dioxide concentrations in the atmosphere have been rising since records have regularly been kept in the 1950s. Carbon dioxide concentrations increase rates have increased from about 1 ppm (part per million on a volume basis) per year in the 1950s to current rates of nearly 2 ppm per year since the 2000s. Other gasses in the atmosphere are increasing, too,, like methane, water vapor, and nitrous oxide as examples. These gasses impact the radiation transfer of both short-wave radiation (visible light) and long-wave radiation (thermal radiation) trapping longer-wave radiation in the earth's atmosphere. This leads to an assumed hypothesis called "green house warming." Green house warming is controversial as many believe it will lead to a temperature increase while other groups believe it might lead to greater cooling. These weather dynamics are complex. Sophisticated weather models called "global circulation models" simulate the global dynamics of the earth's atmosphere and the impacts on weather on temperature and precipitation on a rather large grid basis for the world. These model predictions are somewhat variable for a specific region, like the U.S. Great Plains. This paper reviewed many of the model predictions on Great Plains climate and their impact on predicted irrigation water requirement. The U.S. Great Plains has a known dependence on a declining irrigation resource and a sensitivity and propensity for droughts. Most predictions on global climatic changes on the Great Plains are expected to impact irrigated agriculture. The impacts depended greatly on the global climate model used. Generally, in most cases alfalfa irrigation requirement was predicted to increase, while the predictions were more mixed for corn, with most predictions having a decreased irrigation requirement for winter wheat. Most impacts are expected rather far out (>2050), but the Central Plains producers need to be aware of the favorable chances to utilize these advantageously and for the more adverse impacts to make strategic operational changes to minimize climate impacts. Technical Abstract: Rising carbon dioxide and other green house gasses (water vapor, nitrous oxide, methane, etc.) are predicted to have an effect on future climates. These gasses impact crops and global and local weather. The carbon dioxide increase is generally considered to be favorable to agriculture as it increases plant photosynthesis, decreases plant transpiration, and thereby increases water use efficiency. The greenhouse gasses, however, affect the atmosphere's transmittance of radiation trapping more of the thermal or long-wave radiation in the atmosphere and purportedly leading to an increase in temperature at the earth’s surface. This phenomenon has been called "green house warming." This hypothesis is highly controversial as it highly speculative whether it leads to warming or cooling, more or less precipitation, and its impact on the environment, particularly on agriculture. The U.S. Great Plains is potentially impacted by this change due to its dependence on a declining irrigation resource and its known sensitivity and propensity for droughts. This paper reviewed many past and current scientific reports on the impact of future climate change on irrigated with an emphasis on the Great Plains. Most predictions on global climatic changes on the Great Plains are expected to impact irrigated agriculture. The impacts depended greatly on the global climate model used. Generally, in most cases alfalfa irrigation requirement was predicted to increase, while the predictions were more mixed for corn, with most predictions having a decreased irrigation requirement for winter wheat. Most impacts are expected rather far out (>2050), but the Central Plains producers need to be aware of the favorable chances to utilize these advantageously and for the more adverse impacts to make strategic operational changes to minimize climate impacts. |
