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WARMING_Chicago River ice

Phil Taylor/Medill

If water bodies like the Chicago River fail to freeze over, evaporation speeds up, resulting in the possibility of greater snowfall.

It's not just hot air; climate change could also mean more snow

by Phil Taylor
Feb 27, 2008

Snowiest Chicago winters since 1928-1929 (in inches)

1.                     89.7                 1978-1979
2.                     82.3                 1977-1978
3.                     77.0                 1969-1970
4.                     68.4                 1966-1967
5.                     66.4                 1951-1952
6.                     60.9                 1981-1982
7.                     59.9                 1929-1930
8                      59.5                 1964-1965
9.                     58.9                 1961-1962
10.                   58.3                 1973-1974
11.                   54.5                 2000-2001  
As of 10 a.m. Feb. 26, 2008: 55.9 inches.

Source: Rick Di Maio, Chicago meteorologist

Skeptics on the subject of global warming would point to the heavy amount of snowfall Chicago has experienced this year.     

However, they would be wrong, according to a sampling of scientific opinion.   

Experts caution that there may be more winters like this, where snowfall has so far nearly doubled the norm. But that would be only until it gets too hot to snow, they added.

“l n the simulations I’ve analyzed, you can get some quite big blizzards up until the year 2040,” said Raymond Pierrehumbert, professor of geophysics at the University of Chicago.  “But between 2040 and 2080, it starts to get too warm to have much snow at all and it gradually sort of peters out.”

Climatologists say snowfall is more difficult to predict than rain because it depends on a broader range of factors, such as atmospheric temperature and the la nina phenomenon in  the Pacific Ocean.  What they do agree on, however, is that warmer atmospheres can hold more precipitation.

“When it is very bitterly cold, the air doesn’t hold much water so you can’t get much blizzard,” Pierrehumbert said.  “That’s why some of the most severe blizzards we get happen in unusually cold spring times.”

Chicago had seen 55.9 inches of snow as of Wednesday morning, but is only supposed to have seen about 30 inches by this time of year, said Rick Di Maio, who teaches meteorology at Loyola University in Chicago.  The record for snowfall in Chicago is 89.7 inches, set during the winter of 1978-1979.  The record low was 9.8 inches in 1920-1921.

Of course, one winter season can’t be taken as an indication of future climate patterns.  This year's average winter temperatures will probably end up 2-2.5 degrees Fahrenheit below normal, Di Maio said.

But this season’s precipitation levels, combined with atypical temperature fluctuations, reflect what climate experts say will be some of the side effects of global warming.  A study released last December by the group Environment Illinois suggests global warming will result in more extreme rain and snowfall as warmer temperatures speed up evaporation and allow clouds to hold more precipitation. 

“Higher precipitation is predicted, and unfortunately it’s supposed to come in extreme events,” said Dave Kraft, committee member at Climate Justice Chicago, a coalition of environmental groups hoping to change public perception of global warming. “Was this (season) it? Maybe it’s a sign, maybe it isn’t.”

Experts say precipitation will likely increase in many parts of the country, while others experience drought.  In Illinois, storms with extreme precipitation have become more frequent by 3 percent each decade from 1931 to 1996, according to a study by the Illinois State Water Survey and the National Climatic Data Center.

This winter's snowfall has already melted the city’s snow removal fund, said Wendy Abrams, spokeswoman for the budget department. The Streets and Sanitation Department had spent $20 million on snow removal as of Feb. 18, out of an $18.5 million budget meant to cover snow removal through next December. 

But the thing many environmentalists fear most about global warming in Chicago is not extreme snow or rain, which presents storm water management challenges of its own.  Climate change in Chicago could mean more frequent and more intense heat waves, which are typically amplified in urban areas subject to the “heat island effect.”

One infamous spell in 1995 caused more than 500 fatalities, when temperatures neared 100 F for almost a week.  The city continues to invest money in heat-absorbing technologies like green roofs and green alleys to mitigate the severity of summer heat waves, said Department of Environment spokesman Larry Merritt.

Pierrehumbert, from the University of Chicago, said average global temperatures could increase 3 to 8 degrees Fahrenheit. But heat waves could be much more pronounced in the interiors of large continents, where land can dry out quicker and speed the evaporative effect. 

Despite the risks, Pierrhumbert said many continue to discount the science behind climate change. 

“If you look at the polls, there’s a distressing impression that scientists still disagree about some of the basic physics of global warming,” he said. “What scientists are arguing about is not whether the effect is real, but just how bad it’s going to get.”

"The temperatures in the hottest Augusts in Chicago could be as much as 30 degrees Fahrenheit warmer than they are in say a baseline 2000," he said.