MIDWEST CLIMATE: ABOUT THE TOOL

Climate Trends and Variability in the Midwest

Since the start of modern weather records and before, the climate of the Midwest has been changing. To grasp a further understanding of these changes, this Climate Trends Tool explores observed weather records and climate model analyses to find current and projected climate trends in the Midwest.

The Climate Trends Tool features interactive maps and graphs of annual, seasonal and monthly temperature, precipitation, drought, degree-days and growing season variables. These are provided for both the observed time period, 1895-2016, and future projections.  These maps can be shown for the Midwest, the Useful to Usable (U2U) project region, or for individual Midwest and Plains states.  Statewide and climate division data are both available.

Observed Data

Two datasets were used to calculate the trends for the observed period.  For the average temperature, maximum temperature, minimum temperature, total precipitation, all drought indices, heating degree days, and cooling degree days, the nClimDiv dataset from the National Centers for Environmental Information was used.  The rest of the elements are calculated using a gridded dataset based on Cooperative Observer Network (COOP) data developed by the MRCC. 

Model Data

The future projections are from the North American Regional Climate Change Assessment Program (NARCCAP).  The Climate Trends Tool uses the PSU/NCAR mesoscale model (MM5I) regional climate model driven by the Community Climate System Model (CCSM) atmosphere-ocean general circulation model.  NARCCAP only uses atmosphere-ocean general circulation model forced with the SRES A2 emissions scenario (i.e., high emission scenario).  The current period for this model is 1971-1999 and the future period is 2041-2069. CCSM+MM5I data are not available for the drought indices.

Trend Calculations

The values displayed when hovering over the observed trend map on the left, in the legend of the first graph, or in the table at the bottom of the page are linear trends in units per century. For seasonal and annual values, monthly data for each state or climate division was averaged or totaled to compute the value.  A linear slope was computed from these values to find the amount of change per year.  This slope value was then multiplied by 100 to compute the change per century displayed on the maps and graphs.

Using this Tool

To see the observed data trend value on the map, hover over a state or climate division. To see the difference between the CCSM+MM5I future and current averages, hover over a state or climate division on the map on the right.  Clicking on a particular state or climate division on either map will then display the 1895-2016 observed data time series, the CCSM+MM5I current and future time series, and the table which shows the average and trend values for specific observed and modeled time periods.  Hovering over either graph will show the variable value for each year.  Clicking and dragging on either graph will zoom in on that particular time series.  At any time, these maps and graphs can be printed or downloaded by clicking on the menu in the top right corner of the map or graph.  To see a different region, time scale, or variable, click on Update Map to update the values.

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