Chemicals That Eased One Woe Worsen Another
Monday, July 20, 2009
This is not the funny kind of irony: Scientists say the chemicals that helped solve the last global environmental crisis -- the hole in the ozone layer -- are making the current one worse.
The chemicals, called hydrofluorocarbons (HFCs), were introduced widely in the 1990s to replace ozone-depleting gases used in air conditioners, refrigerators and insulating foam.
They worked: The earth's protective shield seems to be recovering.
But researchers say what's good for ozone is bad for climate change. In the atmosphere, these replacement chemicals act like "super" greenhouse gases, with a heat-trapping power that can be 4,470 times that of carbon dioxide.
Now, scientists say, the world must find replacements for the replacements -- or these super-emissions could cancel out other efforts to stop global warming.
"Whatever targets you thought you were going to make," said David Fahey, a physicist at the National Oceanic and Atmospheric Administration, "it will be undermined by the fact that you have . . . additional emissions that you hadn't planned on."
The colorless, odorless replacement chemicals enter the atmosphere in tiny amounts, often leaking out of refrigerators and air conditioners, or escaping when those machines break and are improperly dumped. They now account for about 2 percent of the climate-warming power of U.S. emissions, according to the Environmental Protection Agency.
That is still far less than carbon dioxide, which is produced by burning fossil fuels and accounts for about 85 percent of the problem. And it is less than the roughly 10 percent of warming from methane, which comes from sources including farm animals and decomposing trash.
But in recent weeks, these obscure gases have been given a higher profile in the carbon-dominated debate on climate change.
Last month, a group of scientists published a paper projecting that, if unchecked, the emissions would rise rapidly over the next 40 years. By 2050, they found, the amount of super greenhouse gases in the atmosphere might be equal to six or more years' worth of carbon dioxide emissions.
And last week, diplomats met in Geneva to discuss ideas for a worldwide reduction in HFCs.
"You have this moment when you could nip this problem in the bud and avoid this very large growth of a dangerous chemical," said David Doniger, policy director at the Natural Resources Defense Council's climate center, from Geneva. "Now, in the next couple of years, is when you have to do this."