So we too should keep a wary eye on those things that seem to be turning up the global thermostat. Or not turning it up, as the case may be. According to a recent issue of the journal Science , the decades-long steady and spectacular increase in the amount of atmospheric methane has stopped. In fact, it stopped in 1991. The rate of increase had been slowing during the 1980s, but measurements taken at 28 sites around the world, and along two shipping routes, showed that by 1992 the rate had plummeted in the Southern Hemisphere and reached zero in the Northern Hemisphere.
Nobody is quite sure why.
Methane is released into the atmosphere by a variety of sources. Other natural methane sources include the digestive processes of cattle and of termites, but the world seemed to hold no fewer termites nor less flatulent bovines in 1991 than 1981. Among the human-caused sources of excess methane is the decomposition associated with landfills, but again, our species is no less trashy than it's ever been. We're a bit more responsible with recycling and composting, but not yet enough to make the difference. And the difference is significant.