December 21, 2023

Analysis: Winter warmth in the U.S. Midwest in the days before Christmas 2023 linked to climate change

December 21, 2023

For the U.S. Midwest states, chances for a White Christmas are looking slim. Climate Central analysis shows that the unusually warm wintertime temperatures forecast over the five days leading up to and including Christmas Day (December 21-25) for much of the Upper Midwest are at least twice as likely due to human-caused climate change

According to the National Weather Service, a White Christmas is defined as at least 1 inch of snow on the ground at 7 am local time on Christmas Day. The historic probability of a White Christmas in this part of the country runs from 40% to 90+%. See the probability for your location, with ready-to-use graphics.

CSI Heat Alert December 2023 US Midwest (EN)

What sort of unusual temperatures are forecast?

  • Daily average temperatures are expected to be 20-35°F above average (based on 1991-2020 climate normals) in some regions during this five-day period – including large parts of Minnesota, Wisconsin, and Iowa

  • Daily temperatures across the Upper Midwest states are generally not expected to dip below 32°F, even at night, for most of the five days leading up to Christmas Day. With forecast temperatures above 32°F, existing snow depth is likely to melt, and conditions are not supportive of falling snow.

  • Temperatures are not expected to dip below 32°F on any day between December 21 and 25 across all of Illinois, much of Iowa, and parts of Minnesota, Wisconsin and Michigan.

What impact is climate change having?

  • During this five-day period leading up to and including Christmas Day, the unusually warm conditions have a strong climate change influence. Most days across the affected states are expected to reach a Climate Shift Index (CSI) level of at least 2, meaning that temperatures in those areas are at least two times more likely because of human-caused climate change. 

  • In large parts of Minnesota, Wisconsin and Iowa, all five days in this period are expected to reach a CSI level of at least 2, while surrounding areas are expected to experience four days at or above CSI level 2.

  • Most of Michigan’s lower peninsula is expected to experience three days of at least CSI 2, while in the upper peninsula, four days are expected to reach at least a 2 on the CSI scale.

  • Some days are expected to reach a CSI level 5 in parts of Minnesota, Wisconsin, Michigan, and surrounding areas. A CSI of 5 indicates an exceptional climate event, where conditions were made at least five times more likely due to climate change.

Use the Climate Shift Index global map to see CSI levels in your city and region. 

How do we know climate change is having an impact?

The Climate Shift Index uses peer-reviewed methodology to estimate how climate change has increased the likelihood of a particular daily temperature. It can be run using historical or forecast temperatures.

Using computer models, we compared the likelihood that these temperatures would occur in a world without carbon emissions released by humans, versus in today's world with decades of carbon emissions building up in the atmosphere. This is an established scientific method to determine how much climate change has or has not affected individual extreme weather events.

For this analysis, temperatures come from the National Center for Environmental Prediction’s Global Forecast System.

What do experts have to say?

Dr. Andrew Pershing, VP of Science at Climate Central, said: 

“People dreaming of a White Christmas will be sorely disappointed this year. As long as people keep burning coal, oil, and natural gas, events like the string of unusually warm temperatures in the Midwest will become more and more common.”

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