{"id":13420,"date":"2025-01-23T22:00:00","date_gmt":"2025-01-23T22:00:00","guid":{"rendered":"https:\/\/modernsciences.org\/staging\/4414\/?p=13420"},"modified":"2025-01-08T05:38:33","modified_gmt":"2025-01-08T05:38:33","slug":"arctic-blast-2025-colder-than-normal-temperature-anomalies-january-2025","status":"publish","type":"post","link":"https:\/\/modernsciences.org\/staging\/4414\/arctic-blast-2025-colder-than-normal-temperature-anomalies-january-2025\/","title":{"rendered":"That Arctic blast can feel brutally cold, but how much colder than \u2018normal\u2019 is it\u00a0really?"},"content":{"rendered":"\n
\n
\n \n
\n Philadelphia Eagles fans braved temperatures in the 20s to watch their team play the New York Giants on Jan. 5, 2025.\n AP Photo\/Chris Szagola<\/a><\/span>\n <\/figcaption>\n <\/figure>\n\n Richard B. (Ricky) Rood<\/a>, University of Michigan<\/a><\/em><\/span>\n\n

An Arctic blast hitting the central and eastern U.S. in early January 2025 has been creating fiercely cold conditions<\/a> in many places. Parts of North Dakota dipped to more than 20 degrees below zero<\/a>, and people as far south as Texas woke up to temperatures in the teens. A snow and ice storm<\/a> across the middle of the country added to the winter chill.<\/p>\n\n

Forecasters warned that temperatures could be \u201c10 to more than 30 degrees below normal<\/a>\u201d across much of the eastern two-thirds of the country during the first full week of the year.<\/p>\n\n

But what does \u201cnormal\u201d actually mean?<\/p>\n\n

While temperature forecasts<\/a> are important to help people stay safe, the comparison to \u201cnormal\u201d can be quite misleading. That\u2019s because what qualifies as normal in forecasts has been changing rapidly over the years as the planet warms.<\/p>\n\n

Defining normal<\/h2>\n\n

One of the most used standards for defining a science-based \u201cnormal\u201d<\/a> is a 30-year average of temperature and precipitation. Every 10 years, the National Center for Environmental Information<\/a> updates these \u201cnormals,\u201d most recently in 2021. The current span considered \u201cnormal\u201d is 1991-2020. Five years ago, it was 1981-2010.<\/p>\n\n

But temperatures have been rising over the past century, and the trend has accelerated since about 1980. This warming is fueled by the mining and burning of fossil fuels that increase carbon dioxide and methane in the atmosphere. These greenhouse gases trap heat close<\/a> to the planet\u2019s surface, leading to increasing temperature.<\/p>\n\n

\n \"Ten<\/a>\n
\n How U.S. temperatures considered \u2018normal\u2019 have changed over the decades. Each 30-year period is compared to the 20th-century average.<\/span>\n NOAA Climate.gov<\/a><\/span>\n <\/figcaption>\n <\/figure>\n\n

Because global temperatures are warming, what\u2019s considered normal is warming, too.<\/p>\n\n

So, when a 2025 cold snap is reported as the difference between the actual temperature and \u201cnormal,\u201d it will appear to be colder and more extreme than if it were compared to an earlier 30-year average.<\/p>\n\n

Thirty years is a significant portion of a human life. For people under age 40 or so, the use of the most recent averaging span might fit with what they have experienced.<\/p>\n\n

But it doesn\u2019t speak to how much the Earth has warmed<\/a>.<\/p>\n\n

How cold snaps today compare to the past<\/h2>\n\n

To see how today\u2019s cold snaps \u2013 or today\u2019s warming \u2013 compare to a time before global warming began to accelerate, NASA scientists use 1951-1980<\/a> as a baseline.<\/p>\n\n

The reason becomes evident when you compare maps.<\/p>\n\n

For example, January 1994 was brutally cold east of the Rocky Mountains. If we compare those 1994 temperatures to today\u2019s \u201cnormal\u201d \u2013 the 1991-2020 period \u2013 the U.S. looks a lot like maps of early January 2025\u2019s temperatures: Large parts of the Midwest and eastern U.S. were more than 7 degrees Fahrenheit (4 degrees Celsius) below \u201cnormal,\u201d and some areas were much colder. <\/p>\n\n

\n \"A<\/a>\n
\n How temperatures in January 1994 compare to the 1991-2020 average, the current 30-year period used to define \u2018normal,\u2019<\/span>\n NASA Goddard Institute for Space Studies<\/a><\/span>\n <\/figcaption>\n <\/figure>\n\n

But if we compare January 1994 to the 1951-1980 baseline instead, that cold spot in the eastern U.S. isn\u2019t quite as large or extreme. <\/p>\n\n

Where the temperatures in some parts of the country in January 1994 approached 14.2 F (7.9 C) colder than normal when compared to the 1991-2020 average, they only approached 12.4 F (6.9 C) colder than the 1951-1980 average. <\/p>\n\n

\n \"A<\/a>\n
\n How temperatures in January 1994 compared to the 1951-1980 average.<\/span>\n NASA Goddard Institute for Space Studies<\/a><\/span>\n <\/figcaption>\n <\/figure>\n\n

As a measure of a changing climate, updating the average 30-year baseline every decade makes warming appear smaller than it is, and it makes cold snaps seem more extreme.<\/p>\n\n

\n \"Charts<\/a>\n
\n Charts show how temperatures have shifted in southwest Minnesota. Each histogram on the left shows 30 years of average January temperatures. Blue is the most recent 30-year period, 1991-2020; yellow is the earlier 1951-1980 period. The bell curves of the frequency of those temperatures show about a 4 F (2.2 C) shift.<\/span>\n Omar Gates\/GLISA, University of Michigan<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\n

Conditions for heavy lake-effect snow<\/h2>\n\n

The U.S. will continue to see cold air outbreaks in winter, but as the Arctic and the rest of the planet warm, the most frigid temperatures of the past will become less common.<\/p>\n\n

That warming trend helps set up a remarkable situation in the Great Lakes that we\u2019re seeing in January 2025: heavy lake-effect snow across a large area.<\/p>\n\n

As cold Arctic air encroached from the north in January, it encountered a Great Lakes basin where the water temperature was still above 40 F (4.4 C)<\/a> in many places. Ice covered less than 2% of the lakes\u2019 surface on Jan. 4.<\/p>\n\n

That cold dry air over warmer open water causes evaporation, providing moisture for lake-effect snow<\/a>. Parts of New York and Ohio along the lakes saw well over a foot of snow<\/a> in the span of a few days.<\/p>\n\n

\n \"Maps<\/a>\n
\n Surface temperatures in much of the Great Lakes were still warm as the cold Arctic air arrived in early January.<\/span>\n Great Lake Environmental Research Laboratory<\/a><\/span>\n <\/figcaption>\n <\/figure>\n\n

The accumulation of heat in the Great Lakes, observed year after year, is leading to fundamental changes in winter weather and the winter economy<\/a> in the states bordering the lakes.<\/p>\n\n

It\u2019s also a reminder of the persistent and growing presence of global warming, even in the midst of a cold air outbreak.\"The<\/p>\n\n

Richard B. (Ricky) Rood<\/a>, Professor Emeritus of Climate and Space Sciences and Engineering, University of Michigan<\/a><\/em><\/span><\/p>\n\n

This article is republished from The Conversation<\/a> under a Creative Commons license. Read the original article<\/a>.<\/p>\n<\/div>\n\n","protected":false},"excerpt":{"rendered":"Philadelphia Eagles fans braved temperatures in the 20s to watch their team play the New York Giants on…\n","protected":false},"author":1051,"featured_media":13422,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","fifu_image_url":"https:\/\/live.staticflickr.com\/7317\/15966216143_57827db331_h.jpg","fifu_image_alt":"","footnotes":""},"categories":[13],"tags":[3658,3661,3646,3653,3662,3656,3647,3652,2588,3651,2591,3655,3648,3659,3650,3657,3649,474,3645,3663,3654,3660],"class_list":{"0":"post-13420","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-earth","8":"tag-30-year-temperature-averages","9":"tag-arctic-air-impacts","10":"tag-arctic-blast-2025","11":"tag-climate-change-baselines","12":"tag-climate-change-impacts-on-weather","13":"tag-climate-change-perception","14":"tag-cold-snaps-historical-comparison","15":"tag-defining-climate-normals","16":"tag-extreme-weather-events","17":"tag-global-temperature-shifts","18":"tag-global-warming-effects","19":"tag-great-lakes-ice-cover","20":"tag-great-lakes-lake-effect-snow","21":"tag-midwest-cold-weather","22":"tag-nasa-1951-1980-baseline","23":"tag-noaa-climate-data","24":"tag-temperature-anomalies","25":"tag-the-conversation","26":"tag-u-s-cold-snap-january","27":"tag-warming-great-lakes-basin","28":"tag-warming-trends","29":"tag-winter-weather-patterns","30":"cs-entry","31":"cs-video-wrap"},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/posts\/13420","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/users\/1051"}],"replies":[{"embeddable":true,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/comments?post=13420"}],"version-history":[{"count":1,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/posts\/13420\/revisions"}],"predecessor-version":[{"id":13421,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/posts\/13420\/revisions\/13421"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/media\/13422"}],"wp:attachment":[{"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/media?parent=13420"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/categories?post=13420"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/tags?post=13420"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}