Illinois State Water Survey - University of Illinois at Urbana-Champaign

State Climatologist Office for Illinois

Future Climate Change Scenarios for Illinois

Using climate models and assumptions about future levels of greenhouse gasses, we can examine scenarios of future changes in temperature and precipitation in Illinois. To be clear, these are "what if" cases, not forecasts or predictions. We are limited in our ability to both understand and model complex climatic processes. Furthermore, research suggests that things like land use changes, regional aerosol emissions, and changes in atmospheric circulation play a large role on the regional scale of climate change. Even if we could perfectly model the Earth's climate, it is impossible to predict future changes in society that will determine future levels of greenhouse gasses. Still, the models give us a glimpse of what future climate changes may be in store for Illinois.

Here we used 21 climate models and two emission scenarios to construct a range of temperatures and precipitation scenarios out to 2100 for Illinois. The results are expressed as departures from the 1971-2000 averages or normals. The emission scenarios are from the 4th IPCC report and represent a high emission scenario (A2) and a low emission scenario (B1). Further details on the emission scenarios are discussed below the graphs. A more extensive discussion of possible scenarios of the future climate of Illinois can be found on the Illinois Water Supply Planning web site.

Key points about the results are:
  • there is no "best" or "most likely" outcome - the results from any of the 21 models are equally likely to occur
  • with both emission scenarios, all models show some degree of warming by 2100;
  • the low emission scenario results in warming ranging from 2 to 7° F;
  • the high emission scenario results in warming ranging from 6 to 12° F;
  • the results for precipitation are less clear cut, showing a wide range of wetter and drier conditions;
  • the low emission scenario results in precipitation ranging from 4 inches below to 4 inches above normal;
  • the high emission scenario results in precipitation ranging from 11 inches below to 8 inches above normal;


Low emission scenario for Illinois
Low emission scenario temperature
High emission scenario temperature results
High emission scenario temperatures
Low emissions scenario precipitation results 
Low emission scenario precipitation
High emission scenario precipitation results
High emission scenario precipitation

Future Emission Scenarios

These emission scenarios were the same used by the latest Intergovernmental Panel on Climate Change (IPCC) report. The high emission scenario assumes a future world with the population growth rate the same as today and uneven economic growth across regions. This is sometimes referred to as the "business as usual" scenario. This results in CO2 concentrations in 2100 of 855 parts per million (ppm). By comparison, the level of CO2 in the atmosphere in 2007 was 385 ppm.

The low emission scenario assumes a future world with the total population leveling off and declining slightly, rapid changes in economic structures toward a service and information economy, with reductions in material intensity, and the introduction of clean and resource-efficient technologies. This results in CO2 concentrations in 2100 of 535 ppm.

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