How Global Climate Change Affects Milwaukee

In a Jan. 23, 2025, post to his “Truth” website, President Donald Trump took advantage of the recent cold spell covering much of the United States to reiterate his belief that global warming is a hoax:

“Record Cold Wave expected to hit 40 States. Rarely seen anything like it before. Could the Environmental Insurrectionists please explain — WHATEVER HAPPENED TO GLOBAL WARMING???”

Trump demonstrates an inability to distinguish between local weather and global temperature trends.

The map below summarizes temperatures around the world on Jan. 23 of this year. Areas shown in blue had temperatures much colder than their normal temperatures. Places colored deep red were hotter than usual. The term used to describe these red and blue territories is “anomalies.”

On Jan. 23, temperatures were notably below average over the eastern part of North America, including Wisconsin and the Great Lakes. Meanwhile, much of coastal North America was abnormally warm.

The next graph, showing results for Feb. 19, shows how quickly temperatures can change. On that day, much of the eastern U.S. was warmer than normal and the western part of the U.S. was cooler than normal.

The next graph shows anomalies in average global land and ocean temperatures in January from 1850 to 2025. Periodically, the temperatures peak, followed by lower temperatures accompanied by claims that global warming has ended. Notably, 2024 and 2025 are the two hottest years on record so far.

How has global warming affected Milwaukee? To explore this question, I looked at temperature measurements taken at Milwaukee’s Mitchell Airport. The blue line on the chart below plots the annual average temperature in degrees Fahrenheit between 1970 and 2025.

The dotted blue line in the chart below shows the linear trend, which takes out the year-to-year variation. Using the trend line, the average temperature of 45.7 degrees in 1970 increased to 50.3 degrees in 2025, a rise of about 4.6 degrees (all in Fahrenheit).

The yellow line plots January temperatures. Using the dotted trend line, average temperatures rose from 17.4 degrees to 26.2 degrees, a rise of 8.8 degrees, or about 50%.

The green line plots July temperatures. They rose from 70.9 degrees to 73.7 degrees, a difference of 2.8 degrees.

The solid line in the next graph shows the number of days between the last freeze in spring and the first freeze in the following fall, essentially consisting of the late days of spring, summer, and the early days of the following autumn. The number of freeze-free days rose from 168 in 1970 to 192 in 2025, an increase of 24 days or 14 percent.

Finally, the next graph plots monthly precipitation at Mitchell. On average, it rose from 2.80 inches to 2.95 inches, an increase of 0.15 inches.

Trump’s statement represents an alarming refusal to accept evidence, which in turn reflects on his ability to make good decisions. While Milwaukee does not face the extreme results of climate change — such as rising sea levels — it will face a wetter and hotter future.