So it’s about 15 degrees out, you slipped on the permafrost coating Foster Street on the way to class and the ice-chunks on Lake Michigan are about wide enough to picnic on. Illinois might be heading for one of its five snowiest years in a century, and last week the city of Evanston admitted it didn’t have enough salt to clear the sidewalks. By all accounts, it has been a pretty miserable winter.
Which, of course, makes it the perfect time to talk about global warming. In recent years, climatologists have begun to drastically improve a technique called downscaling, whereby they measure climate change on an increasingly local level. Rather than talking about the effects of global warming in the United States or Midwest, its becoming easier to discuss the effects even within a single state or even just a few square kilometers. And in Chicago, they’ve found that while the greenhouse effect may make winter a little less frigid, it could also mean more snow, sleet and slush.
Chicago has seen 45.7 inches of snow so far this year, almost eight more than normal. The steady stream of flurries and blizzards has come courtesy of La Nina, the rush of cold water through the Pacific that can cause wet weather in the Midwest, says National Weather Service Meteorologist Tim Halbach. And as Northwestern climatology professor Bradley Sageman says, you can’t necessarily blame today’s weather on a warming planet. “Global warming is a climate phenomenon, which means it is not about the weather, but rather it is about the weather integrated over thousands of square kilometers and decades of time.”
Illinois also hasn’t yet seen the same kind of severe effects from climate change as other parts of the nation. Unlike the Western states where warming trends have been drastic, surface temperatures in the Land of Lincoln have risen just 0.8 degrees (Compare that to North Dakota, which saw a three degree jump in the same period).
Some scientists believe much of the state is in a “warming hole,” a region stretching from the Southeast U.S. up into Illinois that has actually cooled somewhat while the rest of the country has warmed. “There’s not a real sharp line. You can’t say everything south of I-80 is cooling, everything north is warming. In Illinois we kind of get a mixed signal,” says Jim Angel, Illinois’ state climatologist.
There are several theories circulating for why the warming hole exists, including the possibility that soot from coal-fired powered plants has helped cool the air. But scientists don’t doubt that, over time, the area will warm with the rest of the country. And with that warmth, oddly, could come a period of increased snow. “The ideal conditions for heavy snowfall are temperatures around the freezing mark,” Angel says. “If you warm things up so that they’re still cold, but maybe a few degrees warmer, you might get more snow fall in the short term.”
Local climate patterns can often seem to buck wider trends. So in recent years, climatologists have been honing the techniques to model climates for areas as small as single cities. Don Wuebbles, a University of Illinois professor of atmospheric sciences, has spearheaded several recent efforts at regional climate modeling in the U.S., including projects that made long-term predictions for the Northeast and Midwest. He is currently the lead scientist on Mayor Richard Daley’s Chicago Climate Action Plan, which should be releasing its findings in the next month or so, he says. The report will forecast the effects of global warming in the Chicago metropolitan area, while making policy suggestions for coping and cutting down on the city’s carbon emissions.
“What we’ve been able to do particularly well up to this point is do the global average effects,” Wuebbles says. Most global climate models, he explains, break down their maps into 100-to-200 square kilometer areas. “Now what we’re trying to do is … get down to the local scale where all the impacts occur.” That process is still being refined, Wuebbles says. But in the past half-decade climatologists have made big strides. “There definitely are uncertainties associated with what we are doing. We tried to minimize those not only by using the latest downscaling statistical techniques, but also by using the hundred years of historical data we have from the Chicago area.”
In a 2003 study he helped lead for The Union of Concerned Scientists, Wuebbles and his team predicted that by 2095, wintertime in Illinois would look more like present day Arkansas. On average, winter temperatures would rise 7-to-13 degrees farenheit. The warmer temperatures could mean more precipitation across the board.
The snow, slush and rain could also be somewhat erratic. Raymond Pierrehumbert, a University of Chicago professor of geophysical sciences and one of Wuebble’s partners on the Action Plan, says those future winters won’t resemble anything to which the Windy City is accustomed. “Winters won’t look like winters anymore. You’ll still get some big blizzards, but it’ll tend to melt off,” he says. “So the snow accumulation goes down, but the amount goes up a bit.” Using data from the Fourth Intergovernmental Panel on Climate Change, Pierrehumbert ran a 100-year climate model specifically for the Windy City. Most years hover between five and 30 inches, fluctuating with the El Nino cycle. Then, in 2040, his model predicts a 56-inch snow dump. He cautions, however, that predicting snow patterns is notoriously difficult. “You can probably rerun that universe 10 times and you don’t get that big snowfall, it’s sort of luck of the draw.”
But if Chicago might see a few more blizzards, it could be even worse for our Great Lakes neighbors. A 2003 study from Colgate University found that over the last half-century, global warming may have increased the amount of lake effect snow in areas like upstate New York, Northern Ohio and Michigan. “Almost all of the lake effect areas were showing increases (in snowfall) over the past 50 years, whereas the non-lake effect areas were basically flat,” says Adam Burnett, the professor who headed the study. Lake effect snow patterns, which don’t affect Illinois, occur when cold air passes over warm bodies of water, catching water vapor, which then, eventually, turns into precipitation. In trying to explain the rising snowfalls, Burnett’s team blamed warming lake temperatures as the likely culprit.
In their study, Burnett and his co-authors wrote that they expected increase of snow could be temporary, as rising temperatures would eventually make the climate too hot for snow to form. Many assume the same for Illinois. But how temporary is still a question. U. Chicago’s Pierrehumbert says that by midway through the 21st century, he expects the severe snowfalls to tail off. Wuebbles, on the other hand, says models he has seen don’t show that happening until after 2100. Either way, don’t expect to pack away those duck boots any time soon.
