MICHIGAN

   

Figure 1

Figure 1: Observed and projected changes (compared to the 1901–1960 average) in near-surface air temperature for Michigan. Observed data are for 1900–2014. Projected changes for 2006–2100 are from global climate models for two possible futures: one in which greenhouse gas emissions continue to increase (higher emissions) and another in which greenhouse gas emissions increase at a slower rate (lower emissions). Temperatures in Michigan (orange line) have risen about 2°F since the beginning of the 20th century. Shading indicates the range of annual temperatures from the set of models. Observed temperatures are generally within the envelope of model simulations of the historical period (gray shading). Warming is projected to continue through the 21st century, with less warming under a lower emissions future (green shading). Historically unprecedented warming is projected during the 21st century. Less warming is expected under a lower emissions future (the coldest years being about as warm as the hottest year in the historical record; green shading) and more warming under a higher emissions future (the hottest years being about 11°F warmer than the hottest year in the historical record; red shading). Source: CICS-NC and NOAA NCEI.

Michigan has a humid climate with large seasonal changes in temperature. Summers are warm and humid while winters are cold. The Great Lakes play an important role in the state’s climate. The Lower Peninsula is bordered by Lake Michigan to the west and by Lakes Huron and Erie to the east. The Upper Peninsula is bordered by Lake Superior to the north and Lakes Michigan and Huron to the east and south. The lakes moderate the climate, causing Michigan to be more temperate and moist compared to other north-central states. The moderating effect is most evident along the shores, which are considerably warmer during the winter and cooler in the summer compared to more inland locations. For example, Lansing and Muskegon have similar latitudes, but experience very different frequencies of hot and cold days. Lansing, which is located in the center of the state, averages 6.6 days with maximum temperatures above 90°F and 9 days with minimum temperatures below 0°F. In contrast, Muskegon, which is located along the western shore of Lake Michigan, averages only 1.8 days above 90°F and 2.7 days below 0°F each year. The moderating effects are even more striking along the shores of the even colder waters of Lake Superior in the Upper Peninsula. Sault St Marie averages only 1 day above 90°F and there have been only 4 days since 1888 when the nighttime low temperature was above 70°F.

Since the beginning of the 20th century, temperatures in Michigan have risen more than 2°F (Figure 1). Temperatures in the 2000s have been higher than any other historical period. The year 2012 was the hottest on record for the state, with a statewide average temperature of 48.4°F, almost 5°F above the long-term average. This warming has been greatest in the winter and spring while summers have not warmed as much, a feature characteristic of much of the Midwest. This is reflected in a below average occurrence of hot days (maximum temperature above 90°F) (Figure 2a) and no overall trend in warm nights (minimum temperature above 70°F) (Figure 2b). The winter warming trend is reflected in a below average number of very cold nights (minimum temperature below 0°F) over the past two decades (Figure 2c) and reduced ice cover in the Great Lakes. From 2003 to 2013, the average annual maximum ice coverage was less than 43%, compared to the 1962–2013 average of 52%.

Statewide annual precipitation has ranged from a low of 22.68 inches in 1930 to a high of 39.22 inches in 1985. The driest multi-year periods were in the 1930s and early 1960s, and the wettest in the 1980s, early 1990s, and the 2000s (Figure 2d). The driest 5-yr period was 1930-1934 and the wettest was 1982-1986. The year 2013 was the second wettest on record, with the state receiving 38.23 inches of precipitation. Michigan has experienced an increase in the frequency of extreme precipitation events. Over the past decade, the state experienced the highest frequency of 2-inch rain events in the historical record (Figure 3). Snowfall is common in the state, but varies regionally. Due to the proximity of the Great Lakes, the south shore of Lake Superior in the Upper Peninsula and the eastern shore of Lake Michigan in the Lower Peninsula receive much more snowfall than the rest of the state. Parts of the Upper Peninsula receive more than 180 inches annually. The shorelines of Lakes Superior, Michigan, and Huron have experienced significant upward trends in annual snowfall totals.

Water levels in the Great Lakes have fluctuated over a range of three to six feet since the late 19th century. Higher lake levels were generally noted in the latter part of the 19th century and early 20th century (the 1940s, 1950s, and the 1980s). Lower lake levels were observed in the 1920s and 1930s and again in the 1960s. For Lakes Superior and Michigan-Huron, the first decade of the 21st century has also seen lower levels. Trends on the lakes have been relatively small with the exception of Lake Michigan-Huron, which has shown a statistically significant downward trend over the past 150 years. The trend is largely due to the high levels early in the period and the extremely low levels in the past 10 years (Figure 4).

Large increases in temperature are possible for the future if greenhouse gas concentrations continue to increase (Figure 1). Even under a pathway of lower greenhouse gas emissions, average annual temperatures are projected to most likely exceed historical record levels by the middle of the 21st century. However, there is a large range of temperature increases under both pathways and under the lower pathway a few projections are only slightly warmer than historical records. Extreme heat is of particular concern for Detroit and other urban areas where high temperatures combined with high humidity can cause dangerous heat index values, a phenomenon known as the urban heat island effect. Higher spring temperatures will lengthen the growing season, but also potentially increase the risk of spring freeze damage. In 2012, the highest March temperatures on record caused Michigan’s fruit trees to bloom early. When temperatures dropped back down to below freezing in April, the budding fruit crop was destroyed, causing more than $225 million worth of damage, the worst losses to the state’s fruit tree industry since 1945.

Precipitation is projected to increase for Michigan, with increases most likely during the winter and spring (Figure 5). Additionally, extreme precipitation is projected to increase, potentially increasing the frequency and intensity of floods. A greater frequency of heavy precipitation increases the risk of springtime flooding, posing a threat to Michigan’s important agricultural industry by delaying planting and resulting in loss of yield.

The intensity of future droughts is projected to increase. Even if precipitation increases in the future, rising temperatures will increase evaporation rates and the rate of loss of soil moisture. Thus, future summer droughts, a natural part of the Michigan climate, are likely to be more intense.

Changes in seasonal and multi-year precipitation, evaporation, and temperature can affect water levels in the Great Lakes, causing serious environmental and socioeconomic impacts. During the 1980s, high lake levels resulted in the destruction of beaches, erosion of shorelines, and the flooding and destruction of near-shore structures. Low lake levels can affect the supply and quality of water, restrict shipping, and result in the loss of wetlands. Future changes in lake levels are uncertain and the subject of research. Reduced winter ice cover from warmer temperatures leaves shores vulnerable to erosion and flooding.

Resources

1. Bai, X., and J. Wang, 2012: Atmospheric teleconnection patterns associated with severe and mild ice cover on the Great Lakes, 1963–2011. Water Quality Research Journal of Canada 47, 421–435, doi: h10.2166/wqrjc.2012.009.
2. Kunkel, K. E., L. Ensor, M. Palecki, D. Easterling, D. Robinson, K. Hubbard, and K. Redmond, 2009a: Trends in snowfall in the lake effect snow belts of the Laurentian Great Lakes: 1900–2007. J. Great Lakes Res, 35, 23-29.
3. Kunkel, K.E, L.E. Stevens, S.E. Stevens, L. Sun, E. Janssen, D. Wuebbles, S.D. Hilberg, M.S. Timlin, L. Stoecker, N.E. Westcott, and J.G. Dobson, 2013: Regional Climate Trends and Scenarios for the U.S. National Climate Assessment. Part 3. Climate of the Midwest U.S., NOAA Technical Report NESDIS 142-3, 95 pp. [URL]
4. Midwestern Regional Climate Center, cited 2016: “(1981-2010) Maps of gridded data long-term averages; Rainfall – Michigan.” [URL]
5. NOAA, cited 2012: March heat, April freezes, National Oceanic and Atmospheric Administration. [URL]
6. NOAA, cited 2016: Climate at a Glance: U.S. Time Series, published October 2016, retrieved on October 18, 2016, National Oceanic and Atmospheric Administration National Centers for Environmental Information. [URL]
7. NOAA, cited 2016: Great Lakes dashboard, data download, National Oceanic and Atmospheric Administration. [URL]
8. Vose, R.S., D.R. Easterling, K.E. Kunkel, A.N. LeGrande, and M.F. Wehner, 2017: Temperature changes in the United States. In: Climate Science Special Report: Fourth National Climate Assessment, Volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 267-301.