If human CO2 emissions caused the 1995 Chicago heat wave, what caused the 1930s Chicago heat waves?

STLtoday - Chicago plans to slash greenhouse gases

"When I became mayor, 'climate change' wasn't on the radar for most cities, states and nations around the world — or even for most people," Daley said in a written introduction to the plan. "But I believed then and believe even more deeply today that when you do such things as planting trees and creating open space, when you invest resources to remove pollution from the air and encourage the construction of buildings that are smart for the environment, then you enhance quality of life for all the residents of the city."

Officials say Chicago emits 34.6 million metric tons of greenhouse gases each year; add the six surrounding counties and that climbs to 103 million metric tons per year.

If Chicago does not reduce emissions, summer heat indexes in the city could climb as high as 105 degrees — similar to those in Mobile, Ala. — by the end of the century, according to researchers from Texas Tech University in Lubbock and the University of Illinois who were commissioned by the city to study climate change.

Since 1980, Chicago's average temperature has risen approximately 2.6 degrees, 4 degrees in the winter.

"What stands out to people is, how likely will you see a 1995-like heat wave again in the future?" said Katharine Hayhoe, a Texas Tech geosciences researcher. "We don't want to suggest that type of future is inevitable because it's not, but if we wait until that happens, then it is inevitable."

In the Chicago heat wave of 1995, the mercury spiked at 106 degrees, and about 600 people died.

In similar research, scientists with the Netherlands Meteorological Institute found earlier this year that by the end of the century, high temperatures in Chicago would reach 115 degrees.

"If you look at the records in Chicago, we have had the tendency to be moving toward milder weather conditions, the harsh winter seems to have decreased over time," said Jim Angel, climatologist with the Illinois State Water Survey at Champaign.

It's that kind of news that discourages people from trying to prevent climate change, said Suzanne Malec-McKenna, Chicago's environmental commissioner. But she said the city had to try.

"There's certainly going to be cynicism about this, but this is the direction the city as a whole knows we need to go in," Malec-McKenna said. "We think it's very doable and it needs to be aggressive. It needs to spark people's imaginations."

1995 Chicago heat wave - Wikipedia, the free encyclopedia

Most of the heat wave victims were the elderly poor living in the heart of the city, who either had no working air conditioning or could not afford to turn it on. Many older citizens were also hesitant to open windows and doors at night for fear of crime.[6] Elderly women, who may have been more socially engaged, were less vulnerable than elderly men. By contrast, during the heat waves of the 1930s, many residents slept outside in the parks or along the shore of Lake Michigan.[2]
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Impacts in the Chicago urban center were exacerbated by an urban heat island that raised nocturnal temperatures by more than 2 °C (3.60 °F).[9] Urban heat islands are caused by the concentration of buildings and pavement in urban areas, which tend to absorb more heat in the day and radiate less heat at night into their immediate surroundings than comparable rural sites. Therefore, built-up areas get hotter and stay hotter.

Other aggravating factors were inadequate warnings, power failures, inadequate ambulance service and hospital facilities, and lack of preparedness.