The Greenhouse What?
I've had some questions about the greenhouse effect and greenhouse gases, so I figured now would be as good a time as any to provide a little overview of the subject.
First of all, it's important to note that the greenhouse effect and global warming are NOT the same thing. Greenhouse gases and the greenhouse effect have always been with us, and in fact makes the Earth habitable. If the Earth had no atmosphere, it would average about 30 degrees Celsius (about 50 degrees Farenheit) lower than it does at present.
(Image From Global Warming Art)
So how does the atmosphere help keep the Earth warm? Most of the sun's radiation has a short wavelength. It's mostly in and near the visible parts of the spectrum. The atmosphere is mostly transparent to visible light, which is absorbed by the Earth's surface. As the surface warms, it radiates longer wavelength radiation which warms the atmosphere. Those areas which receive more sunlight warm the most, and land warms much faster than water. And of course, some surfaces on the land absorb more of the sun's radiation and heat up faster, as anyone who has walked from a grassy park onto an asphalt parking lot on a hot July afternoon knows. The radiation absorbed by the atmosphere is then emitted in all directions, some going back to Earth, some going out to space. This whole process is complicated further by the presence of clouds, which can reflect some of the incoming solar radiation and can also prevent the day's heating from escaping back to space at night.
Greenhouse gases include water vapor (the most abundant by far), carbon dioxide and methane. The concern among many climate scientists is that increasing amounts of CO2 will increase the overall global temperature (global warming) and have a damaging effect on the Earth's climate.
Here's a good resource on bad greenhouse meteorology.
Comments (4)
In addition to the thermal transport cycles in the atmosphere, there is also a chemical cycle at work. If the CO2 is taken up by plants, the effect is balanced because the plants eventually return the carbon as either CO2 or methane. However, the carbonic acid formed by water in the atmosphere puts CO2 into the ground and water bodies. This is the source of sea shells and limestone and is part of a cycle measured in millions of years. If it wasn't for volcanic action returning this CO2 back to the air, the earth would be a cold dead rock.
Posted by Jerome Borden | November 10, 2006 10:39 AM
Please be in the habit of acknowledging the original sources of your images.
http://www.globalwarmingart.com/wiki/Image:Greenhouse_Effect_png
Thank you.
Posted by Robert A. Rohde | November 13, 2006 4:01 AM
What's interesting in the discussion on global warming, is that it seems only the atmospheric/ solar inputs are considered as heat sources. What about heat from the interior of the planet? This variability seems a much more likely source of heat causing the abrupt changes documented in the geologic record. It appears the separation of scientific disciplines keeps the blinders on certain institutionalized bias. When the variability of volcanic eruptions, earthquakes, hydrothermal venting and other geothermal sources are implemented within climate models we might begin to have a serious discussion. Till then, the chaos and butterfly theorist can say anything they like, cause it appears simply as empty rhetoric.
Posted by Bruce | November 15, 2006 1:14 AM
If the Earth had no atmosphere, it would average about 30 degrees Celsius (about 50 degrees Farenheit) lower than it does at present.
Fahrenheit is actually spelled with an h.
Posted by Chris | December 24, 2006 11:29 AM