National Geographic News
Tired of global warming? Get used to it.
Even if humans stop burning oil and coal tomorrownot likelywe've already spewed enough greenhouse gases into the atmosphere to cause temperatures to warm and sea levels to rise for at least another century.
That's the message from two studies appearing in tomorrow's issue of the journal Science.
Researchers used computer models of the global climate system to put numbers to the concept of thermal inertiathe idea that global climate changes are delayed because it water takes longer to heat up and cool off than air does. The oceans are the primary drivers of the global climate.
"Even if you stabilize the concentration of greenhouse gases, you are still committed to a certain amount of climate change no matter what you do because of the lag in the ocean," said Gerald Meehl, a climate scientist with the National Center for Atmospheric Research in Boulder, Colorado.
Greenhouse gases such as carbon dioxide collect in the atmosphere and are believed to act as a blanket, trapping heat and causing the Earth to warm. To stop this warming, many scientists say humans must reduce the amount of greenhouse gases they emit.
Human activities that make the largest contributions to greenhouse gases include exhaust fumes from automobiles and commercial jets and emissions from power stations and factories.
"The longer you wait to do something, the more climate change you are committed to in the future," Meehl said.
Meehl co-authored one of the Science studies. He and his colleagues found that even if no more greenhouse gases are added to the atmosphere, globally averaged air surface temperatures will rise about 1 degree Fahrenheit (0.5 degree Celsius) and global sea levels will rise at least 4.3 inches (11 centimeters) by 2100.
The sea level rise estimate is conservative, because the models Meehl and colleagues used only account for thermal expansionwater expands as it warms, causing sea levels to rise. Melting glaciers and ice sheets will likely at least double the sea level rise.
Since humans are unlikely to stop pumping greenhouse gases into the atmosphere anytime soon, Meehl and his colleagues also ran their computer models under scenarios in which the gases continue to accumulate at low, medium, and high rates.
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