GWS.TV
Explaining the basics of global warming
“The science behind global warming is fundamentally simple and powerful,” says Dr. Knute Nadelhoffer, professor of ecology and evolutionary biology at the University of Michigan. “We know based on ice core records that before 1940, the concentration of C02 in the atmosphere—one of the primary global warming gases–was below 300 parts per million for at least 600,000 to 700,000 years—and probably longer.
“Since the middle of the last century we have gone from 300 parts per million to 385 parts per million. C02 is a warming gas. It reflects warming radiation back to the earth and keeps some of the heat from escaping to space. That is also very well known—the physical properties of C02 and other greenhouse gases such as methane, 
which is also increasing. N20, or nitrous oxide, which is also increasing. These are all radiatively active gasses which reflect heat back to the earth’s surface. We know that all three of these gases are increasing.”
“We’re now approaching 390 parts per million—a higher concentration than has ever existed in human civilized history. When you consider that the human species is only a million years old, we’re living in an atmosphere that we’ve never lived in before.”
How will global warming impact delicate ecosystems? “As temperature and moisture conditions change, the conditions for organisms change,” says Nadelhoffer. “So we can expect, in the Chicago area for example, that certain tree species that have evolved to survive and reproduce in our region will no longer do that. They’ll survive in areas further north that are climatically similar to what we have today.
“Different plant species will migrate at different rates, animals that depend on them will come and go….things will change.”
Dr. Nadelhoffer is a science adviser to the Environmental Law & Policy Center.
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