climate change in Chicago

Factual Questions
1

I heard a talk last year at the Notebaert Nature Museum by Jim Angel, a state climatologist for Illinois. He analyzed weather data from the Midway Airport, which he recommended as a good source of weather data for the region because the airport has weather data for a century. Another reason why weather data from the airport is reliable is because the airport has been surrounded by city for the whole century, so there isn’t an effect of increasing urbanization, which would itself make temperatures warmer at a site. Angel said that low temperatures at night have been getting warmer over the century. Also, rainstorms have been getting more intense, though the average amount of rain that Chicago gets during a year isn’t changing.

For more information:

Illinois State Climatologist’s Office, FAQ about Illinois climate data—

http://www.sws.uiuc.edu/atmos/statecli/index.htm

http://www.sws.uiuc.edu/atmos/statecli/FAQ/faq.htm

Rainfall and temperature records from Midway airport:

http://www4.ncdc.noaa.gov/cgi-win/wwcgi.dll?wwDI~StnSrch~StnID~20005916
Original article:
http://chicago.straightdope.com/sdc20090625.php

2

Did he say what “rainstorms have been getting more intense” means, if not more rainfall than in the past?

3

It seems like it could mean that we’re getting a lot more thunderstorms and torrential downpours, and fewer just lightly rainy days. That could keep the region getting the same amount of rain every year, while also increasing the intensity of rainstorms.

Still, I’d love some clarification too.

4

I remember Jim Angel saying at his talk that his analysis of weather records from Midway Airport showed that rainfall events (average amount of precipitation in one storm) are getting heavier, but the total amount of rain we get in a year hasn’t changed. He suggested that we also would be getting more periods of drought in Illinois because we would have fewer storms, but I’m not sure whether he analyzed data to check this idea directly. I think that he also mentioned that we will be getting more flooding in Chicago, partly because of the increased intensity of storms, but also partly because we’ve paved the entire city and the water can’t sink into the ground.