The New York Times reports that the City of Chicago has been developing plans that will enable the City to adapt to global warming. The City commissioned climatologists to model the impact that global emissions of carbon dioxide could have on Chicago's climate. According to the model, if global emissions continue at their current rate, by the end of the 21st century Chicago will have as many as 72 summer days with high temperatures over 90 degrees; for most of the 20th century, Chicago experienced on average fewer than 15 such days, and the intensity of summer heat predicted by the model is similar to that in the Deep South. A risk assessment firm forecasted that changes of that magnitude could multiply heat-related deaths, increase freezes and thaws that damage buildings, bridges, and roads, and warm winters enough that termites could for the first time survive in Chicago and damage wooden building frames.
Faced with those threats, former Mayor Richard Daley urged City departments to evaluate what adaptations would do the most good and were economically and politically feasible. Changes to pavement and trees were among the priorities. Alleys, streets, and parking lots cover nearly 40 percent of Chicago, and these impermeable surfaces concentrate rainfall, which contributes to routine flooding of Chicago basements and sewers during storms, and storms are expected to intensify and be more frequent in a warmer and wetter future. To alleviate this problem, the City has begun replacing streets and alleys with permeable pavers that allow 80 percent of rainwater to filter through to the ground below. Arborists also advised the City to stop planting some of Chicago's most common trees, including the most prevalent, ash trees, and to add varieties better suited to a warm climate, including the bald cypress, an iconic tree of the South (which even currently can be cultivated in Northern states).
The New York Times article is available at: http://www.nytimes.com/2011/05/23/science/earth/23adaptation.html?pagewanted=1&_r=1&hp