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Over the last 100 years, average temperatures near the Earths surface have increased by about 1 degree.
For Illinoisans who have shivered through winter freezes as low as minus 36 degrees and baked in summer heat reaching 117 degrees, it may be hard to muster any concern when climate scientists warn that worldwide temperatures have increased by 1 degree over the last century. But a preponderance of evidence, now accepted by the vast majority of the worlds climate scientists, proves that we are in a period of global warming. Evidence also shows that human activities are partly to blameperhaps mostly to blame. And if it continues, climate models suggest the increase will accelerate through the end of this century, with temperatures rising as much as 11 degrees by 2100.
The most heated debate about global warming is not whether it exists (many skeptics concede that its real), but just how much of it can be blamed on human activity and whether there are reasonable and effective measures we can take to prevent it.
As for the human part of the equation, the main problem is our burning of fossil fuels and clearing of forests, which releases 8 billion metric tons of carbon dioxide (CO2) into the atmosphere each year. CO2 is known as a greenhouse gas because it traps radiant energy from the sun. Greenhouse gases help prevent the planet from sinking into a deep freeze that would make it uninhabitable, but it is possible to have too much of a good thing. Excessive greenhouse gases have been trapping more radiant heat over the last century. Unfortunately, this trend may become self-sustaining at some point, and, in a worst-case scenario, it could speed up so fast that we would be helpless to stop it.
What about the skeptics? Lets not automatically dismiss them as lackeys for money-grubbing industrialists. (OK, maybe a few of them do have unethical motives.) But there actually are natural causes of global warming to consider. For one thing, we are coming out of a Little Ice Agea modest temperature drop that began around the time of the Renaissance Period and ended after the American Revolution. The oceans currents can have a huge impact on weather and climate. Also, changes in solar activity influence the climate. And as for greenhouse gases, theyre also released through natural causes such as volcanoes or wildfires.
Even so, most scientists are convinced the human impact on climate change is significant. What theyve found is that a 1 degree temperature increase has already had a disturbing effect on the planet.
Next week: Its getting hot, Part 2: Effects of warming
From the Feb. 28-March 6, 2007, issue