Banning Chemicals To Protect Ozone May Aggravate Global Warming, Atmospheric Scientist Says

"By independently addressing the issues of ozone depletion and global warming, we are jeopardizing desirable options for one effect based on lesser -- or even inconsequential -- impacts on the other," said Don Wuebbles, director of the Environmental Council at the U. of I. and a professor of atmospheric sciences. "We need to stop looking at these issues as though they are separate from one another, and start considering them together when we determine environmental policy."

In the Nov. 7 issue of the journal Science, Wuebbles and colleague James Calm, an engineering consultant in Great Falls, Va., write that the regulatory actions on certain chemicals -- imposed by both the Montreal Protocol and the U.S. Clean Air Act to protect the ozone layer -- will have little impact on stratospheric ozone while contributing unnecessarily to global warming.

"Most of the chemicals responsible for ozone depletion are also greenhouse gases," Wuebbles said. "Chlorofluorocarbons [CFCs], for example, tend to be severe offenders for both the depletion of ozone and for global warming. The need for their regulation is unambiguous."

But there are other industrially important chemicals that fall into the gray area. "Some hydrochlorofluorocarbons [HCFCs], for example, have very short atmospheric lifetimes and mostly decompose before reaching the upper atmosphere," Wuebbles said. "Effects on ozone depletion from some of these compounds are likely to be negligible. Nevertheless, they are still being tightly regulated and eventually the intention of the rulings is that they be banned entirely."

One such chemical, HCFC-123, is a high-performance refrigerant commonly used in the cooling systems of large buildings. Some of the intended replacements for HCFC-123 not only have much longer atmospheric lifetimes that could contribute to global warming, but they also are far less energy efficient.

"High efficiency translates into reduced emissions of carbon dioxide and other greenhouse gases from associated energy use, which, in net impact, dwarf those from incidental releases of the refrigerant itself," Wuebbles said. "High efficiency also reduces fuel and other resource requirements.

"It is probable that HCFC-123 and several other CFC replacements would have survived the ban if the global warming regulations had been implemented before the ones for ozone," Wuebbles said. "With keener awareness of the more limited options to reduce global warming, the framers of the Montreal Protocol and the U.S. Clean Air Act might have been more cautious in rejecting chemicals with minimal impacts and offsetting benefits.

"There are many other chemicals that also have special uses, small impacts, and where the replacements for them would cause other problems or issues," Wuebbles said. "In such cases, it might make more sense to reconsider current policy and allow the continued use of some chemicals."