Let it Rain
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Let It Rain

The Warm, Wet World of Climate Change

Published in the EarthSphere Blog. Cover Image: Let it Rain by WM House (©2022 Archean Enterprises LLC; ArcheanArt)

Headlines bemoan how the US is baking, England swelters, and Southern Europe is on fire (just like California). Let’s not forget the American SW, which is turning into dust as the Colorado River dries up and forty million people argue over its water. A person could be forgiven for thinking only of fire, drought, heat, and melting ice sheets when the subject of climate change comes up. But a warming planet also means more rain.

Karachi made the news yesterday as public services collapsed, businesses closed, and 15 people perished in floodwaters. An entire month of rain fell in one night. The coastal city is Karachi, Pakistan, is home to 16 million people, and the city is no stranger to monsoon rains. But meteorological experts say the frequency and intensity of these summer rains are increasing.

Trundling along through our daily lives on this small backwater planet called Earth, we are subject to the whims of fundamental physics. One relevant and inescapable reality is that warm air holds more moisture than cold air. Thus, by its very nature, global warming means the atmosphere delivers more precipitation than five decades ago. However, before getting carried away, be aware that this basic principle does not predict wetter weather everywhere. Climate patterns are shifting under the influence of global warming. The weather is becoming more unpredictable. The net effect is that some areas experience more drought while others adjust to wetter conditions.

A New Reality

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 in the Pacific NW, Mid-Continent, and Eastern US has 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.

A fascinating 2021 article in the NYT tells the story of two Americas: one parched and one soaked. Their feature image shows the eastern half of the US bathed in cool bluish-green splotches of color, indicating long-term increases in annual precipitation. But, the western US is dominated by tans and browns, indicating desiccation and drought.

An increasingly frequent weather pattern called the ‘Mid-West water hose’ results in more rain and flooding through the middle of the US. This weather phenomenon starts in the open skies over the Gulf of Mexico. High temperatures and sunlight boost evaporation, resulting in moisture-laden air flowing northward. The warm moist air rides up and over a cooler, denser atmospheric layer when it gets to the Mid-West, creating rain.

No Escape

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.

River flooding is one of the obvious results of more rain and snow. Because of the human propensity to settle in cities and farms near rivers, flooding brings with it a large dose of human misery. This morning, as if on cue, CNN reported record rainfall and widespread flash flooding in the St. Louis area. A cosmic coincidence, no doubt.

2021 paper in the Proceedings of the National Academy of Sciences estimates that 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, to Anthropogenic climate change.

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 how we all live our lives. Life 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.


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.