Let It Rain Shifting Weather Patterns
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Shifting Weather Patterns and More Rain

A Warmer Earth Brings Changes

(Published in The EarthSphere Blog)

Too much water or too little water, both generate environmental headaches, but since water is a limiting factor for both urban and rural life, the continuing twenty-year-long drought in the American West garners lots of headlines. When the two largest man-made reservoirs in the United States (Lake Mead and Lake Powell) reached record low levels this year, it triggered a federal mandate to implement water rationing. But the entire country is not in a drought, and many areas are receiving more rain than average. Climate change and global warming are shifting weather patterns.

By its very nature, global warming means the atmosphere delivers more precipitation than five decades ago because basic physics dictates that warm air holds more moisture than cooler air. This fundamental principle should not be interpreted to predict a wetter Earth everywhere. Weather patterns are resetting under the influence of climate change. The net effect is, some areas experience more drought while other areas adjust to wetter conditions.

The United States is a microcosm of this new global reality. Over the last two decades, average precipitation in the Colorado River drainage basin has decreased, meaning less water for the 40 million people who depend on the river for their sustenance. On the flip side, precipitation levels for the Pacific NW, Mid-Continent, and Eastern U.S. have stayed level or steadily increased since 1901. Some of the largest changes occurred in the Northeast and the northern Mid-West around the Great Lakes.

The American Mid-West

Wisconsin, Michigan, Minnesota, Illinois, Indiana, and Ohio have seen 10 to 20 percent increases in precipitation since 1901, and some areas recorded over a 20 to 30 percent increase. A warmer Earth generates more evaporation, and the atmosphere holds more water, but how this extra moisture gets distributed depends on large-scale weather patterns.

The American Mid Continent from Texas and Louisiana north to the Great Lakes recorded long-term increases in precipitation between 1901 and today, making their climate increasingly wetter. This change generated a wide range of effects impacting cities, farms, and regional ecosystems.

River flooding is one of the obvious results of more rain and snow. Because of the human propensity to locate cities and farms near rivers, flooding brings with it a large dose of human misery. A 2021 paper in the Proceedings of the National Academy of Sciences estimated about a third of the cost of flood damage in the Mid-West between 1988 and 2017 was related to long-term increases in annual precipitation, and hence related to anthropogenic climate change.

But the effects of a wetter environment don’t stop with flooding. Agriculture must respond to these changes with crops that thrive in wetter, warmer conditions. The USDA points out that higher temperatures may negatively affect pollination patterns, plant productivity, and existing crop rotation schedules. A wetter climate with increased precipitation also results in more runoff, creating soil erosion and degrading soil quality.

American agriculture has a proven history of adaptation in combating disruptive circumstances. Still, it may not be business as usual, and wetter weather along with an increase in extreme events will provide challenges to American farmers.

Precipitation Driven by the Midwest Water Hose

study from the University of Iowa points to human-induced climate change as one driver of an increasingly frequent weather pattern called the “Midwest water hose.” This weather phenomenon starts at the southern end of the country, in the open skies over the Gulf of Mexico. There, high temperatures and sunlight boost evaporation resulting in moisture-laden air that flows northward. The warm moist air rides up and over a cooler, denser atmospheric layer when it gets to the Mid-West.

As the Gulf of Mexico air rises, moisture condenses, and rain drenches the land below. Researchers say the Midwest water hose accounted for 70% of the region’s annual precipitation in 2019. They also predict the frequency of the Midwest water hose and other extreme weather events will increase in the future.

Climate change presents us with a mixed bag of changing weather patterns for our future. Warmer conditions will increase the amount of evaporation and transpiration, pumping more moisture into an atmosphere with a greater capacity for water retention. In areas not receiving significant rain, droughts and megadroughts present challenges to large populations as the heat leads to significantly dryer conditions. At the same time, the water-laden atmosphere will find places to unload, making other areas wetter and more flood-prone.

People who believe climate change is a problem that won’t affect them are in for a rude awakening. Shifting weather patterns will force changes in the way we all live our lives. Patterns of living for individuals and society at large will be altered by the Anthropocene world we have all helped to create. In plain language, “we must reap what we sow.


Related Articles:

Water and Megadroughts (by WM House; ArcheanWeb)

Climate Change and Water (by WM House; ArcheanWeb)

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Sources:

Climate Change Indicators: U.S. and Global Precipitation (Source: EPA)

Climate change-driven ‘Midwest water hose’ caused massive 2019 flooding in Iowa, elsewhere, UI researchers find (by Donnelle Eller; Des Moines Register)

Contribution of historical precipitation change to US flood damages (by Frances V. Davenport, Marshall Burke, and Noah S. Diffenbaugh; PNAS)

Climate Change and Agriculture in the United States: Effects and Adaptation (Source: USDA)

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.