NOAA Report Finds Efforts to Protect Earth's Ozone Layer Also Helped Slow Climate Change

An international agreement to reduce ozone-depleting chemicals, based in part on science conducted in the 1980s by National Oceanic & Atmospheric Administration (NOAA) scientists and their colleagues, also has slowed global warming by years. These findings were announced on March 9 by researchers at the NOAA Earth System Research Lab and their partners.

The researchers also found that the double effect occurred because compounds that destroy the atmosphere's ozone layer also act as greenhouse gases.

The ozone layer shields the Earth from harmful ultraviolet radiation. To protect this layer, nations around the world signed the Montreal Protocol in 1987 to control the production and use of ozone-depleting substances.

"Science conducted by NOAA scientists and their colleagues provided the scientific basis for the framers of the Montreal Protocol," said Conrad Lautenbacher, Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator. "This is an example of how NOAA's science informs those who make decisions that affect our daily lives. This new study also illustrates the multiplier effect of NOAA's targeted research and its benefits on multiple sectors of science."

While protecting the ozone layer, the Montreal Protocol also has cut in half the amount of greenhouse warming caused by ozone-destroying chemicals that would have occurred by 2010 had these substances continued to build unabated in Earth's atmosphere, according to the study. The amount of warming that was avoided is equivalent to 7 to 12 years of rise in carbon dioxide concentrations in the atmosphere.

"The participants in the Montreal Protocol have done something very good for our climate," said NOAA Earth System Research Lab scientist David Fahey, one of the authors. "While addressing ozone depletion, they also provided an early start on slowing climate change."

The amount of greenhouse gases curbed by the Montreal Protocol is equivalent to five times the reduction target for the first phase of the Kyoto Protocol, a 2005 international agreement to address climate change, according to the scientists. The Kyoto Protocol did not regulate ozone-depleting chemicals because the prior agreements of the Montreal Protocol had already dealt with them, the researchers said.

Earlier studies showed that continued growth in ozone-depleting substances would lead to significant heating of Earth's climate. The new analysis quantifies the near-term climate benefits of controlling these substances.

The researchers also explored options for reducing future use of ozone-depleting substances, such as collecting and destroying chemical storage banks in old refrigerators and air conditioners, choosing substitutes with low climate-warming impact and evaluating the feasibility of further reducing overall emissions of the substances. Additionally, the scientists also considered the impact of voluntary chemical restrictions that began in 1975 in some countries. When these earlier reductions are taken into account, the amount of additional heating of Earth's climate that would have occurred by 2010 is far greater than that avoided since 1987 when the Montreal Protocol went into effect, though the exact amount of the total benefit is uncertain.

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This article originally appeared in the 03/01/2007 issue of Environmental Protection.