Though 40-degree temperatures might still not be balmy enough to break out a beach towel, January 2023 was the warmest January on record for Ann Arbor over the past decade, and the seventh-warmest ever. State and national trends showed similar temperature trends, according to data from the National Oceanic and Atmospheric Administration, with 2023 marking the second-warmest January on record for Detroit and the sixth-warmest across the nation.
Ann Arbor’s average temperature during the month was 32.3 degrees Fahrenheit, which is 6.8 degrees higher than the monthly average over the past 10 years, according to NOAA data. Meanwhile, the average January 2023 temperature in Detroit was 33.5 degrees Fahrenheit, 7.1 degrees higher than the decade average.
Increases in temperature have been getting higher over the past couple of years, with the warmest January day in Ann Arbor peaking at 56 degrees Fahrenheit on Jan. 4, 2023, up 15 degrees from the recorded highest temperature last year.
Jack Urquhart, Environment and Sustainability graduate student at the University of Michigan, said he has studied weather trends in his environmental coursework and how they are impacted by climate change. He noted that the warmer temperatures in January were especially noticeable at the beginning of the month.
“We had a pretty unseasonably warm period earlier in the month,” Urquhart said. “Globally, climate change definitely has an impact on climate broadly, but (unusual weather) can occur from a warm front moving up from the South.”
Urquhart’s observations about the warmer temperatures toward the start of January are corroborated by NOAA’s daily record, with increased high temperatures in Ann Arbor being concentrated in the first couple of weeks and average temperatures consistently dropping below 30 degrees Fahrenheit toward the end of the month.
Richard Rood, professor of climate and space sciences, told The Michigan Daily the mild January weather could be from a combination of annual weather variability and the long-term effects of climate change. Rood explained that warm air moving up from the Gulf area and the southern Atlantic Ocean have contributed to warmer weather in northern states like Michigan this winter. That effect is exacerbated by climate change, according to Rood.
“We’ve always had those (weather) patterns,” Rood said. “Everything is warmer (farther) south than it used to be, (so) when we get that pattern, it’s warmer than it used to be. So it’s a combination of both (weather patterns and climate change).”
Rood mentioned the position of the polar jet streams — strong, cold winds that blow from west to east that can influence temperatures across a large region — as one weather pattern behind the unusually warm winter. For parts of January, Rood said there were no polar jet streams over southeast Michigan, leading to warmer temperatures.
According to Rood, another pattern that plays a role in winter weather is the polar vortex, which is a low-pressure area of cold air that comes from the North Pole. The vortex occasionally expands, bringing cold air into Michigan and other parts of the northern U.S., leading to freezing temperatures such as those seen in late December 2022. However, the polar vortex was notably absent in January 2023, Rood said.
“The polar vortex has always been there,” Rood said. “The polar vortex is still there. You’re just not seeing the cold parts of it this (month) … there have always been patterns where the vortex is more circular (or) the vortex is more wavy.”
Rood noted that polar vortex patterns may also be influenced by climate change.
“The behavior of the vortex is probably changing as the climate warms,” Rood said. “That’s actually a relatively controversial research topic at this point, though there is some indication that the vortex is changing.”
Temperatures all around the world have been consistently rising over the last several decades, with the average global temperature going up by 2 degrees Fahrenheit since the start of the post-industrial era in 1880. The overall increase in temperatures is often the most noticeable in the winter, Rood said, when people expecting a winter chill are instead met with a warm breeze.
“The most robust signal (of climate change) is that temperatures are going up globally,” Rood said. “But if you look regionally … in a place like Michigan, the temperature is rising fastest in winter.”
Rackham student Veronika Lubeck, who is studying geospatial data science, told The Daily that even though a mild winter may be enjoyable for some, she believes the warm weather is concerning since it could be symptomatic of climate change.
“I would definitely say (this January) has been warmer than usual,” Lubeck said. “Climate change could be a contributing factor. Winters are getting a lot more mild … in the Midwest recently.”
Daily Staff Reporter Nadia Taeckens can be reached at taeckens@umich.edu.