Does October snow contradict climate change theory? Absolutely not.


Julia Poska | October 30, 2019

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Map from Iowa Environmental Mesonet (accessed through Des Moines Register).

Iowans across much of the state awoke Tuesday morning to find a blanket of fresh snow atop vibrant orange and yellow autumn leaves, many still attached to the trees. Parts of east and east central Iowa saw as much as three to four inches, according to the Des Moines Register. 

The National Weather Service  puts the average date of first one-inch snowfall in eastern Iowa in early December.  The unseasonable flurry might have some Iowans questioning how serious Midwestern climate change could really be.

But climate (average temperature and precipitation over several decades) is not the same as weather (daily atmospheric conditions). Years of abnormally high snowfall or abnormally cold weather could have an impact on the averages that create our “climate,” but snow, frost and even “polar vortex” events on their own are products of normal weather variation throughout the year.

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Records show that overall, average annual temperatures in Iowa and most of the world are increasing, despite weather variation. This pushes local 30-year climate averages (shown below for Iowa City) up by small increments over time.

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From U.S. Climate Data

 

Iowans can still expect snow and cold in coming decades, though the overall frequency and intensity of such events may decline over time. Somewhat milder winters will be followed by much hotter, dryer summers, with an increased number of intense rainstorms added to the mix.

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