Methane Gas
Methane gas is another naturally occurring greenhouse gas. It is produced as a result of microbial activity in the absence of oxygen. Pre-industrial concentrations of methane were about 700 ppb and in 1994 they were up 145 percent to 1720 ppb. Molecule per molecule methane traps heat 20 times more effectively than carbon dioxide. However, because its atmospheric concentration is much smaller, its direct radiative forcing is just 0.47Wm-2, or 19 percent of the total for long-lived greenhouse gases.
The following are some sources of methane gas
- Natural wetlands or bogs
- Rice paddies
- Cattle
- Termites
- Drilling for oil
- Landfills
- Biomass burning
- Coal mining.
The rate of increase of methane gas in the atmosphere has decreased from 20 ppb annually in the 1980s to just 8 ppb in 1993. So the outlook for stabilizing methane concentrations seems to be better than for carbon dioxide. Anthropogenic sources account for 70 percent of the methane produced annually.
Click to find sources of methane gas.
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