Emissions of Key Greenhouse Gas Stabilize

brian0918 writes "Multiple news sites are reporting that levels of the second most important greenhouse gas, methane, have stabilized". From Scientific American: "During the two decades of measurements, methane underwent double-digit growth as a constituent of our atmosphere, rising from 1,520 parts per billion by volume (ppbv) in 1978 to 1,767 ppbv in 1998. But the most recent measurements have revealed that methane levels are barely rising anymore — and it is unclear why." From NewScientist: "Although this is good news, it does not mean that methane levels will not rise again, and that carbon dioxide remains the 800-pound gorilla of climate change."

Comments

Re:Wait a minute...

[Morphine007]

<sarcasm>Actually, no. Our knowledge is complete. Visit the Creationism Museum to learn more.</sarcasm>

Fixed that for you...

Re:Water Vapor?

[catchblue22]

If you want a detailed answer to this question, go to realclimate.org

Here is a somewhat more brief answer, based on what I have read: Water vapor is a greenhouse gas, but it is quite different than CO2 in that individual water molecules spend relatively little time in the atmosphere before returning to liquid form. CO2 molecules have a far longer lifetime in the atmosphere than water molecules, especially if you consider the relatively short time they spend bound up in plants that will eventually decay and release the CO2 again. The main way to remove the carbon molecule from the system is to bury it, perhaps as sediment at the bottom of the ocean. An important fact to realize is that once we remove carbon from the ground by for example pumping oil, that carbon will remain in the atmospheric system for a very long time.

If I understand the scientific ideas correctly, because the amount of liquid water on the Earth's surface is so large, the actual amount of water vapor in the atmosphere is not limited by the absolute quantity of liquid water. Think of two indoor swimming pools, both with the same surface area, but one being deep and one being shallow. The amount of water vapor in the air will depend on the temperature of the water, the temperature of the air, and surface areas of the pools, among other things. The amount of water vapor in the air is not related to the depth of the pools. Contrast this with CO2 concentrations in the atmosphere, which are related to the absolute amounts existing in the atmospheric system.

So, the amount of water vapor in the atmosphere is controlled by factors such as temperature, sunlight, and other atmospheric conditions. Water vapor concentration changes in response to other factors, and is thus not considered a driver of climate. Carbon dioxide persists in the atmospheric system, and thus is considered a driver of climate.

I hope I have summarized the theories correctly. However if you want a better explanation, then go to the source. realclimate.org, or better yet find some real scientific papers on the subject.