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Montreal Protocol Success Slowed Global Warming


Slow down in global warming linked to phase out of CFCs, and methane reductions

Earlier pauses in warming from Great Depression, World Wars

Washington, D.C., 11 November 2013 - Scientists using sophisticated statistical methods show in a paper in Nature Geoscience that the successful phase out of chlorofluorocarbons, or CFCs, by the Montreal Protocol slowed climate change, contributing to a lower rate of global warming since the early 1990s.

“The statistical analysis confirms that the Montreal Protocol is not only the world’s most successful environmental treaty, but also the most successful climate treaty,” said Durwood Zaelke, President of the Institute for Governance & Sustainable Development. “The treaty not only solved the world’s first great threat to the global atmosphere—the destruction of the stratospheric ozone layer—it also has solved a significant part of climate change, as the same chemicals that destroy the ozone layer are also powerful greenhouse gases.”

“The Montreal Protocol is now nearing a consensus on an amendment to phase down CFC replacements called hydrofluorocarbons, or HFCs, that are super greenhouse gases,” Zaelke added.

Climate vulnerable island states have been advocating the HFC phase down under the Montreal Protocol for the past six years, and more than 100 other countries are supporting this strategy, including China, South Africa, the European Union, and the United States.

“There are few climate policies with this degree of support,” said Zaelke. “India is really the only country now needed to complete the consensus to phase down HFCs. India’s agreement will let the Montreal Protocol take the single biggest, fastest bite out of the climate problem.” A recent paper by Yangyang Xu at Scripps Institution of Oceanography, Zaelke, and others calculates that phasing down HFCs could avoid up to a half a degree Celsius of global average temperature rise by 2100. (See IGSD Press Release on HFC paper.)

The new paper by Francisco Estrada and others analyzed temperature data, together with trends in emissions of greenhouse gases including CFCs, methane, and carbon dioxide. They identified other human causes of the pauses in warming, including reductions in methane emissions from changes in agricultural practices, the Great Depression, and World War I and II.

The Estrada paper concludes that “reductions in greenhouse gas emissions are effective in slowing the rate of warming in the short term.”

“Knowing how much the Montreal Protocol has already done to protect the climate and how much it can do in the future by phasing down HFCs should give us a sense of urgent optimism that we can still meet the challenge of climate change,” Zaelke said.

The abstract to the article, Statistically derived contributions of diverse human influences to twentieth-century temperature changes, by Francisco Estrada, Pierre Perron & Benjamín Martínez-López, is here.

The IGSD Primer on HFCs is here.