The Search Is On for Atmospheric Vandals
HERE'S an environmental gambit for dinner table conversation. What do burps of cattle and nylon stockings have in common? Answer: They both may contribute to global warming. These are just two of the novel factors scientists now are scrutinizing as they try to understand the complex chemistry that enhances the atmosphere's ability to trap heat - the so-called greenhouse effect.
Carbon dioxide (CO DvP6F2&gt;2) has received the most publicity. Released when fossil fuels burn, this heat-trapping gas is building up in the atmosphere. But even if the rise in CO DvP6F2&gt;2 concentration were stopped entirely, there still would be a potential global-warming problem. Growing concentrations of other heat-trapping gases, taken together, can contribute as much to the greenhouse effect as CO DvP6F2&gt;2.
Methane is a leading culprit. Its atmospheric concentration rises about 1 percent a year. Atmospheric chemists don't fully understand where all of it comes from or what happens to it in the air. Natural wetlands may be the largest single source, accounting for about 20 percent of the annual accumulation. Agriculture contributes other important sources. Scientists suspect that bacteria in the digestive systems of ruminants (cud-chewing animals) may produce as much as 15 percent of the annual methane outp ut.
But the ruminants' contribution has been hard to pin down. So the United States Environmental Protection Agency is funding studies at Washington State University and the National Center for Atmospheric Research in Boulder, Colo., to measure cattle methane production. Washington State researchers Brian Lamb, Kris Johnson, and Hal Westberg are to fit hundreds of cattle with plastic and cloth packs to measure actual methane output.
Summarized that way, it sounds like a candidate for the one-time Golden Fleece award former Wisconsin Sen. William Proxmire gave for foolish use of government money. But it is important data gathering. Scientists need facts about methane sources if they are to move beyond speculation and uncertain estimates in trying to gauge the climate role of this gas.
Nitrous oxide is another elusive global-warming factor. It also attacks Earth's stratospheric ozone layer, which absorbs solar ultraviolet radiation. Its atmospheric concentration is growing about 0.2 percent a year. While that is not as fast as methane's rise, it still is significant. The gas has an atmospheric lifetime of some 150 years.
Scientists trying to understand the atmospheric role of this gas haven't been able to find all of its sources either. Some of them may be quite unexpected, as chemists Mark H. Thiemens and William C. Trogler of the University of California at La Jolla have discovered.
In a research paper recently published in Science, they show that nylon manufacture may account for up to 10 percent of the rise in atmospheric concentration of this ozone-destroying, climate-warming gas. This is a source that could be eliminated by changing nylon production processes.
Human activity has reached a scale where it is changing atmospheric chemistry in significant and still poorly known ways. Curbing CO DvP6F2&gt;2 output through energy conservation and other measures is a strategy worth pursuing. But we should realize that this alone will not protect Earth from our atmospheric vandalism.