Climate Change is Already Here
Would you be surprised to learn that climate change has already impacted Michigan in meaningful ways? Or that our weather has grown more severe? Or that some major cities have even seen double digit increases in annual rainfall?
Michigan’s climate is changing because the Earth is warming. Rapid industrialization throughout the 19th and 20th centuries released excess carbon dioxide and related greenhouse gases into the atmosphere. The greenhouse gases act like an Earth-sized blanket trapping heat. We say excess because the Earth has a natural climate cycle that plays out over a factor of 100s of thousands of years (as seen below). Only now, man-made greenhouse gas emissions are rapidly pushing the climate outside of its natural boundaries.
Weather Versus Climate Change
Scientists track several statistics about our world: temperature, humidity, atmospheric pressure, wind, precipitation, and atmospheric particle count. When we measure them over several hours, days or even weeks, we call it the weather.
Weather is volatile. It is difficult to predict and small variations have major short terms effects. Weather is not climate. To find a region’s climate, we take the average of each statistic over a much longer period of time — generally 30 years.
There are two 30-year periods that scientists most often use to discuss Michigan’s current climate: 1951 — 1980 and 1981 — 2010. As we talk about specifics of the changing climate, we are analyzing the difference in the averages between those two periods.
How has Climate Change Already Impacted Michigan?
Wetter Days: Annual precipitation in Michigan increased on average by 4.5%. Southern areas of the state measured increases of approximately 8–13%. Ann Arbor experienced a 25% increase in annual precipitation.
Warmer Air: Michigan’s annual average air temperature increased by 1.2°F. Average winter month temperatures — December to February — increased 2.3°F.
Warmer Water: Summer surface water temperatures — measured from July to September — increased 4.5° on Lake Superior. The Great Lakes are thawing earlier and freezing later.
The frost-free season length, defined as the period between the last occurrence of 32°F in the spring and the first occurrence of 32°F in the fall, has increased in each U.S. region during 1991-2012 relative to 1901-1960. Increases in frost-free season length correspond to similar increases in growing season length.
(Figure source: NOAA NCDC / CICS-NC)