Chicago’s downtown buildings are slowly sinking. The culprit? Underground climate change, study shows.

Two levels below ground at the Grant Park North Garage, the summer heat feels oppressive. As downtown commuters park and exit their cars, sweat quickly beads on their furrowed brows and foreheads. Alessandro Rotta Loria pinched two fingers to zoom into a map on his phone, trying to locate a temperature sensor. Finally, he found the white, pocket-size instrument, inconspicuously zip-tied to a pipe next to a red column. Using a wireless network of more than 150 of these sensors above and below ground across the Loop, Rotta Loria, a Northwestern University assistant professor of civil and environ...