A Warming Globe and A Cooling Atmosphere |
 Dave Thurlow, Host |
Due to the greenhouse effect, the earth's atmosphere IS getting warmer. In fact, 1998 was the warmest year on record. But while we're feeling the heat here at the bottom of the atmosphere, the upper atmosphere is actually cooling. Hi, I'm Dave Thurlow and this is The Weather Notebook.
Scientists studying global warming have mostly been concerned with the lowest layer of the atmosphere, because that's where we human beings tend to hang out. But, those who do study the upper atmosphere find that it is cooling. In fact, one layer of the upper atmosphere, called the mesosphere, has been cooling by as much as a degree every year for 30-years.
The cause of the big chill - a process called radiative cooling. The lower atmosphere is warmed by heat radiating from the surface of the planet. Greenhouse gases trap this heat close to the ground, warming the atmosphere from the bottom up. The more heat in the lower atmosphere, the less heat in the upper atmosphere. So, because of the greenhouse effect, the lower atmosphere heats up and the upper atmosphere cools down.
So, what's the big deal? Well, the big deal is that as the temperature of the upper atmosphere decreases, so to does the ozone layer. It's thought that by the year 2020, parts of the upper atmosphere will be 15 to 20 degrees colder than they are now, due to the greenhouse effect. In that event, ozone loss would double.
Now don't think the end of the world is near. This research is still very much in the early stages and the upper atmosphere is still largely unknown. But the cooling of the upper atmosphere is the latest and biggest signal that the lower atmosphere is heating up.
For more information, be sure to visit our website at weathernotebook.org. Thanks to Subaru and the National Science Foundation.
Related Links
The Heat Is On - New Scientist
Earth in the Balance - Articles from the World Book™