Coldest of the Cold
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As the world warms, the intensity and frequency of extreme cold are both decreasing, as the lowest temperature observed each year is trending upward in most U.S. cities.
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For much of the U.S. east of the Rockies, middle to late January tends to be the coldest time of the year. Even though extreme cold can still happen in winter, as was seen earlier this year in much of the country, the frequency and intensity of extreme cold is declining as the world warms from the increase in greenhouse gases. Digging deeper, this week’s analysis examines the coldest night each year in cities across the country, and in most cases, the trend in that coldest night is warmer.
With no change in the rate of greenhouse gas emissions, warming of the lowest temperature of the year will continue. According to the 2017 U.S. Climate Science Special Report, that coldest reading each year will rise several degrees in parts of the U.S. by the middle of this century. The warming will be most prevalent in the Upper Midwest, across the Great Lakes, and in the Northeast, where up to 10°F of warming is projected.
While the decrease in cold may sound good on a cold winter day, that warming comes with consequences for farming, recreation, economy, and the environment. Fruit trees, which need to become dormant over the winter to bloom in the spring, may produce smaller yields. Winter-based activities in colder climates, like skiing and snowmobiling will become less prevalent, and the tourist economies that support them may struggle. More disease-carrying insects, like ticks and mosquitoes will survive through a milder winter.
METHODOLOGY: To be consistent with previous releases, minimum temperature data for individual sites is through 2017. We have prepared a list of the lowest temperatures of 2018 in each city through January 19 if you would like to add a point representing 2018 to the graphic. Projections are from the 2017 U.S. Climate Science Special Report. Changes in minimum temperature extremes reflect the difference between the average for mid-century (2036-65) and near present (1976-2005) under the RCP8.5 emissions scenario, and are derived from 32 downscaled climate models. Former Weather Channel meteorologist Guy Walton maintains a comprehensive records database, analyzing monthly, annual, and decadal records trends based on NCEI data.