Thursday, December 23, 2010
Global Warming Basics: The Facts as Best We Know Them, Without the Name Calling
The science is not settled, but it should be respected.
Global warming requires an open, honest, mature discussion. Unfortunately, most participants on both sides are more content with shouting each other down. Those on the left see global warming as without question caused by man and as a repudiation of free enterprise, which failure requires massive state intervention to correct before it's too late. Those on the political right dismiss man-made global warming as a hoax, and they often comment that the earth can take care of itself no matter what we throw at it. Both attitudes are far too cavalier.
Global warming does occur. Resulting warmer atmosphere undoubtedly tends toward stronger weather patterns and storms. Increased water vapor tends toward greater atmospheric warming. It is convenient for those who argue on either side of the issue to forget such facts as these. Both sides need to demonstrate integrity by reminding each other what the real debate is rather than using lack of clarity as an opportunity to score political points against one's opponent.
You know what it's like to be in a parked car on even a mild day with the windows rolled up? It's easily hotter inside the car than outside. A "greenhouse gas" (GHG) functions similar to your car windows--infrared heat rays make it inside the earth's atmosphere, but they can't as readily escape.
Greenhouse gases absorb and emit thermal infrared radiation. Nitrogen and oxygen make up 99 percent of earth's atmosphere, but, because they are not affected by infrared light, they are not greenhouse gases. If they were, earth would be much hotter. As non-GHG's, if they made up 100 percent of atmospheric gases, much more heat would be radiated back out into space, and earth's average temperature would be somewhere around 60 degrees farenheit, leaving many more parts of the earth uninhabitable due to cold temperatures.
By relative abundance in the atmosphere, the three primary greenhouse gases are water vapor, carbon dioxide, and methane.
Water vapor accounts for as much as 85% of the greenhouse effect when cloud cover is present. Water vapor does not have near the staying power in the atmosphere as methane and (especially) carbon dioxide, however.
Compared to CO2, the same amount of methane has a much higher contribution to global warming. Methane concentrations in the atmosphere have increased from 750 parts per billion (ppb) in 1750 to about 1850 ppb today. Great amounts of methane can be found in the earth's crust, including what is trapped in permafrost areas of the globe. It is feared that warmer temperatures will thaw permafrost regions and release large additional amounts of methane into the atmosphere, but permafrost methane leakage is not very well understood yet. It is such a new concern that it was not even mentioned in the Intergovernmental Panel on Climate Change's (IPCC) 2007 report. Increased leaking of methane from beneath the ocean floor is causing similar concerns.
Since 1960, atmospheric levels of carbon dioxide have increased from 310 parts per million (ppm) to 390 ppm. Human activities, it is believed, have caused CO2 concentration in the atmosphere to increase by one third since the beginning of the industrial revolution. Current studies show that humans release at least 100 times more CO2 into the atmosphere than do volcanoes.
The earth's average temperature has increased by about 1 degree Fahrenheit since 1905. It is unclear how much of the warming can be attributed to other causes, such as solar activity or climatic cycles. Recent research into the variability of solar radiation indicates that the sun may be a larger contributor than previously thought.
It is possible that all of the warming could be from non-human origin, but the probability of this is very low, because the present trend of greenhouse gas concentration in the atmosphere is a historical anomaly.
Read the "Global Warming Basics" series: