John Roach, National Geographic News 8 Sep 09;
In the fight against global warming, most innovations have been targeting the greenhouse gas "supervillain" carbon dioxide.
Meanwhile, several "henchmen" gases—some even more potent than CO2—have also been building up in Earth's atmosphere.
For now, none of these gases is as big a worry as CO2, due to its higher levels in the atmosphere. But if left unchecked, experts warn, these other compounds could create major new climate change battlefronts.
"The truth is we don't really have room for [these gases] to grow, in terms of the state that we are in with climate change," said Jay Gulledge, a senior scientist at the Pew Center on Global Climate Change in Arlington, Virginia.
"It is happening more rapidly than [it was] projected to happen."
Nitrous Oxide, aka "The Joker"
Most recently scientists warned that nitrous oxide, also known as laughing gas, already accounts for roughly 6 percent of the gases that fuel human-caused climate change.
The main culprit is animal manure, which releases N2O into the atmosphere, according to a new study by Eric Davidson, a senior scientist at the Woods Hole Research Center in Falmouth, Massachusetts.
Nitrous oxide emissions are first produced when fertilizer is added to the soil to grow animal feed. Animals then concentrate nitrogen inside their feces and urine, and soil microbes interact with the released waste to create N2O.
Burning fossil fuels, manufacturing nylon, and other industrial activities also emit the greenhouse gas, Davidson reported last week in the journal Nature Geoscience.
"If we just go on with business as usual with increasing food production, particularly increasing meat production, nitrous oxide will become an even bigger problem," Davidson said.
Manure management should therefore be part of future plans to combat climate change, the scientist concludes, and the Pew Center's Gulledge agreed.
One idea would be to set up a cap-and-trade scheme for farmers to encourage them to reduce their N2O emissions, Gulledge said. This would allow farmers who find ways to pollute less to sell their credits to, for example, carbon dioxide emitters.
"The caveat is we don't have a system for verifying those reductions," Gulledge said.
Methane, aka "Clayface"
In addition to laughing gas, scientists have their eyes on methane, the second largest contributor to climate change.
Methane accounts for about 15 percent of the warming that has occurred in the past century, Gulledge noted, and is 20 to 25 times more powerful than carbon dioxide.
"There is a potential for large amounts of methane to be emitted from natural systems as they warm," he noted.
For example, scientists are concerned that huge deposits of methane locked up in underwater permafrost around Earth's Poles could be released as oceans soak up heat and the frozen soil starts to melt.
And some evidence suggests methane is already being "belched" into the atmosphere as aboveground Arctic soils thaw.
"Right now we still control the composition of the atmosphere by our human activities," Gulledge said.
"If we pass a point where there's large scale thawing of these northern soils … we will no longer be able to control that."
Synthetic Refrigerants, aka "Mr. Freeze"
The other worrisome greenhouse goons are synthetic gases used as refrigerants, in heavy industry, and in consumer electronics.
Many are replacements for chlorofluorocarbons, or CFCs, which were phased out from sources such as refrigerators and air conditioners in the 1990s to prevent destruction of the Earth's ozone layer.
"The new replacements don't destroy ozone, but they are still greenhouse gases," Gulledge said.
These include hydrofluorocarbons, which come standard in today's air conditioners and refrigerators, and perfluorocarbons, which are used in the manufacture of semiconductors.
Sulfur hexafluoride is widely used in the electrical-utility industry to insulate high voltage equipment. The compound is 22,000 times more potent of a greenhouse gas than carbon dioxide over a hundred-year period.
Nitrogen trifluoride is used to make consumer electronics such as high-definition televisions, and it's about 17,000 times more potent than carbon dioxide.
"Anytime a building is built or a computer is made, these kinds of chemicals are being used," Gulledge said. "So they are increasing in the atmosphere."
For now, though, concentrations of synthetic gases are only about a millionth that of carbon dioxide and thus have little effect on global climate, Gulledge said.
And unlike carbon dioxide, these gases should be easy to reduce, he added.
"Our economy is based on fossil fuels, and that makes CO2 much harder to manage," Gulledge said.
"The other things [are] currently a very small part of the overall warming effect, and we can use our modern innovation technology process to figure out ways to phase them out."
