This website is the digital version of the 2014 National Climate Assessment, produced in collaboration with the U.S. Global Change Research Program.

For the official version, please refer to the PDF in the downloads section. The downloadable PDF is the official version of the 2014 National Climate Assessment.

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Welcome to the National Climate Assessment

The National Climate Assessment summarizes the impacts of climate change on the United States, now and in the future.

A team of more than 300 experts guided by a 60-member Federal Advisory Committee produced the report, which was extensively reviewed by the public and experts, including federal agencies and a panel of the National Academy of Sciences.

Explore the effects of climate change
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Extreme heat, heavy downpours, and flooding will affect infrastructure, health, agriculture, forestry, transportation, air and water quality, and more. Climate change will also exacerbate a range of risks to the Great Lakes.

Explore how climate change is affecting the Midwest.



The Midwest region includes the states of Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin. The Highlights section below offers a high-level overview of climate change impacts on this region, including the six Key Messages and selected topics. (see Ch. 18: Midwest)

Key Message: Impacts to Agriculture

In the next few decades, longer growing seasons and rising carbon dioxide levels will increase yields of some crops, though those benefits will be progressively offset by extreme weather events. Though adaptation options can reduce some of the detrimental effects, in the long term, the combined stresses associated with climate change are expected to decrease agricultural productivity.

Key Message: Forest Composition

The composition of the region’s forests is expected to change as rising temperatures drive habitats for many tree species northward. The role of the region’s forests as a net absorber of carbon is at risk from disruptions to forest ecosystems, in part due to climate change.

Key Message: Public Health Risks

Increased heat wave intensity and frequency, increased humidity, degraded air quality, and reduced water quality will increase public health risks.

Key Message: Fossil-Fuel Dependent Electricity System

The Midwest has a highly energy-intensive economy with per capita emissions of greenhouse gases more than 20% higher than the national average. The region also has a large and increasingly utilized potential to reduce emissions that cause climate change.

Key Message: Increased Rainfall and Flooding

Extreme rainfall events and flooding have increased during the last century, and these trends are expected to continue, causing erosion, declining water quality, and negative impacts on transportation, agriculture, human health, and infrastructure.

Key Message: Increased Risks to the Great Lakes

Climate change will exacerbate a range of risks to the Great Lakes, including changes in the range and distribution of certain fish species, increased invasive species and harmful blooms of algae, and declining beach health. Ice cover declines will lengthen the commercial navigation season.


The Midwest’s agricultural lands, forests, Great Lakes, industrial activities, and cities are all vulnerable to climate variability and climate change. Climate change will tend to amplify existing risks climate poses to people, ecosystems, and infrastructure. Direct effects will include increased heat stress, flooding, drought, and late spring freezes. Climate change also alters pests and disease prevalence, competition from non-native or opportunistic native species, ecosystem disturbances, land-use change, landscape fragmentation, atmospheric and watershed pollutants, and economic shocks such as crop failures, reduced yields, or toxic blooms of algae due to extreme weather events. These added stresses, together with the direct effects of climate change, are projected to alter ecosystem and socioeconomic patterns and processes in ways that most people in the region would consider detrimental.

Projected Climate Change

Projected Mid-Century Temperature Changes in the Midwest

Days above 95º FCooling Degree DaysHeavy Precipitation

Temperatures above 95°F are associated with negative human health impacts and suppressed agricultural yields. The frequency of these days is projected to increase by mid-century.

Cooling degree days (a measure of energy demand for air conditioning) are also projected to increase, leading to potential increases in the seasonality and annual total electricity demand.

The frequency of days with very heavy precipitation (the wettest 2% of days) is also projected to increase, raising the risk of floods and nutrient pollution.


Projections above from global climate models are shown for 2041-2070 as compared to 1971-2000 under an emissions scenario that assumes continued increases in heat-trapping gases (A2 scenario). (Figure source: NOAA NCDC / CICS-NC)

Great Lakes Ice Cover Decline

Great Lakes Ice Cover Decline

Great Lakes ice coverage has declined substantially, as shown by these decade averages of annual maximum ice coverage since reliable measurements began, although there is substantial variability from year to year. Less ice, coupled with more frequent and intense storms,1 leaves shores vulnerable to erosion and flooding and could harm property and fish habitat.2,3,4 Reduced ice cover also has the potential to lengthen the shipping season.5 The navigation season increased by an average of eight days between 1994 and 2011. Increased shipping days benefit commerce but could also increase shoreline scouring and bring in more invasive species.5,6,7(Figure source: Data updated from Bai and Wang 20128).


Flood in Cedar Falls

The city of Cedar Falls’ new floodplain ordinance expands zoning restrictions from the 100-year floodplain to the 500-year floodplain to better reflect the flood risks experienced by this and other Midwest cities during the 2008 floods.9

Cedar Rapids has also taken significant steps to reduce future flood damage, with buyouts of more than 1,000 properties, and numerous buildings adapted with flood protection measures.

Some cities have begun to incorporate adaptation planning for a range of climate change impacts. Chicago was one of the first cities to officially integrate climate adaptation into a citywide plan. Since the Climate Adaptation Plan’s release, a number of strategies have been implemented to help the city manage heat, protect forests, and enhance green design, using techniques such as green roofs.10

Most of the Midwest’s population lives in urban environments. Climate change may intensify other stresses on urban dwellers and vegetation, including increased atmospheric pollution, heat island effects, a highly variable water cycle, and frequent exposure to new pests and diseases. Further, many of the cities have aging infrastructure and are particularly vulnerable to climate change related flooding and life-threatening heat waves. The increase in heavy downpours has contributed to the discharge of untreated sewage due to excess water in combined sewage-overflow systems in a number of cities in the Midwest.11

Much of the region’s fisheries, recreation, tourism, and commerce depend on the Great Lakes and expansive northern forests, which already face pollution and invasive species pressures – pressures exacerbated by climate change.

Extreme weather events will influence future crop yields more than changes in average temperature or annual precipitation. High temperatures during early spring, for example, can decimate fruit crop production12 when early heat causes premature plant budding that exposes flowers to later cold injury, as happened in 2002, and again in 2012, to Michigan’s $60 million tart cherry crop. Springtime cold air outbreaks are projected to continue to occur throughout this century.13

Any increased productivity of some crops due to higher temperatures, longer growing seasons, and elevated carbon dioxide concentrations could be offset by water limitations and other stressors.14,15,16,17 Heat waves during pollination of field crops such as corn and soybean also reduce yields.18 Wetter springs may reduce crop yields and profits,19 especially if growers are forced to switch to late-planted, shorter-season varieties.


  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:10.2166/wqrjc.2012.009. | Detail

  2. ,, 2008: City of Chicago Climate Action Plan: Our City. Our Future. 57 pp. URL | Detail

  3. Ferris, G., 2009: State of the Great Lakes 2009. Climate change: Ice duration on the Great Lakes. Environment Canada and United States Environmental Protection Agency. URL | Detail

  4. Gu, L., P. J. Hanson, M. W. Post, D. P. Kaiser, B. Yang, R. Nemani, S. G. Pallardy, and T. Meyers, 2008: The 2007 eastern US spring freezes: Increased cold damage in a warming world? BioScience, 58, 253-262, doi:10.1641/b580311. URL | Detail

  5. Hatfield, J. L., K. J. Boote, B. A. Kimball, L. H. Ziska, R. C. Izaurralde, D. Ort, A. M. Thomson, and D. Wolfe, 2011: Climate impacts on agriculture: Implications for crop production. Agronomy Journal, 103, 351-370, doi:10.2134/agronj2010.0303. | Detail

  6. Hellmann, J. J., J. E. Byers, B. G. Bierwagen, and J. S. Dukes, 2008: Five potential consequences of climate change for invasive species. Conservation Biology, 22, 534-543, doi:10.1111/j.1523-1739.2008.00951.x. URL | Detail

  7. Leakey, A. D. B., 2009: Rising atmospheric carbon dioxide concentration and the future of C4 crops for food and fuel. Proceedings of the Royal Society B: Biological Sciences, 276, 2333-2343, doi:10.1098/rspb.2008.1517. URL | Detail

  8. Lobell, D. B., and C. B. Field, 2007: Global scale climate - crop yield relationships and the impacts of recent warming. Environmental Research Letters, 2, doi:10.1088/1748-9326/2/1/014002. URL | Detail

  9. Mackey, S., 2012: Great Lakes nearshore and coastal systems. U.S. National Climate Assessment Midwest Technical Input Report, J. Winkler, Andresen, J., Hatfield, J., Bidwell, D., and Brown, D., Eds., Great Lakes Integrated Sciences and Assessments (GLISA), National Laboratory for Agriculture and the Environment, 14. URL | Detail

  10. Maus, E., 2013: Case Studies in Floodplain Regulation. 14 pp. URL | Detail

  11. Millerd, F., 2011: The potential impact of climate change on Great Lakes international shipping. Climatic Change, 104, 629-652, doi:10.1007/s10584-010-9872-z. | Detail

  12. Patz, J. A., S. J. Vavrus, C. K. Uejio, and S. L. McLellan, 2008: Climate change and waterborne disease risk in the Great Lakes region of the US. American Journal of Preventive Medicine, 35, 451-458, doi:10.1016/j.amepre.2008.08.026. URL | Detail

  13. Pryor, S. C., R. J. Barthelmie, D. T. Young, E. S. Takle, R. W. Arritt, D. Flory, W. J. Gutowski, Jr., A. Nunes, and J. Roads, 2009: Wind speed trends over the contiguous United States. Journal of Geophysical Research, 114, 2169-8996, doi:10.1029/2008JD011416. | Detail

  14. Rosenzweig, C., F. N. Tubiello, R. Goldberg, E. Mills, and J. Bloomfield, 2002: Increased crop damage in the US from excess precipitation under climate change. Global Environmental Change, 12, 197-202, doi:10.1016/S0959-3780(02)00008-0. | Detail

  15. Sage, R. F., and D. S. Kubien, 2003: Quo vadis C4? An ecophysiological perspective on global change and the future of C4 plants. Photosynthesis Research, 77, 209-225, doi:10.1023/a:1025882003661. | Detail

  16. Smith, A. L., N. Hewitt, N. Klenk, D. R. Bazely, N. Yan, S. Wood, I. Henriques, J. I. MacLellan, and C. Lipsig-Mummé, 2012: Effects of climate change on the distribution of invasive alien species in Canada: A knowledge synthesis of range change projections in a warming world. Environmental Reviews, 20, 1-16, doi:10.1139/a11-020. | Detail

  17. Vavrus, S., J. E. Walsh, W. L. Chapman, and D. Portis, 2006: The behavior of extreme cold air outbreaks under greenhouse warming. International Journal of Climatology, 26, 1133-1147, doi:10.1002/joc.1301. | Detail

  18. Winkler, J. A., J. Andresen, J. Bisanz, G. Guentchev, J. Nugent, K. Primsopa, N. Rothwell, C. Zavalloni, J. Clark, H. K. Min, A. Pollyea, and H. Prawiranta, 2013: Ch. 8: Michigan’s tart cherry industry: Vulnerability to climate variability and change. Climate Change in the Midwest: Impacts, Risks, Vulnerability and Adaptation, S.C. Pryor, Ed., Indiana University Press, 104-116. | Detail

  19. Wuebbles, D. J., K. Hayhoe, and J. Parzen, 2010: Introduction: Assessing the effects of climate change on Chicago and the Great Lakes. Journal of Great Lakes Research, 36, 1-6, doi:10.1016/j.jglr.2009.09.009. | Detail

The National Climate Assessment summarizes the impacts of climate change on the United States, now and in the future.

A team of more than 300 experts guided by a 60-member Federal Advisory Committee produced the report, which was extensively reviewed by the public and experts, including federal agencies and a panel of the National Academy of Sciences.

United States Global Change Research Program logo United States Global Change Research Program participating agency logos