Published online 22 June 2009 | Nature | doi:10.1038/4591040a

Corrected online:

News

Environmentalists push for tougher regulation of chemicals meant to help the ozone layer.

Air-conditioning in cars is a major HFC source. Alan Schein Photogr./Corbis

Modern refrigerants designed to protect the ozone layer are poised to become a major contributor to global warming because of their future explosive growth in the developing world, scientists report this week.

Hydrofluorocarbon chemicals (HFCs) were developed to phase out ozone-depleting gases, in response to the Montreal Protocol. But they can be hundreds or thousands of times more powerful than carbon dioxide as greenhouse gases in trapping heat. HFCs are deployed in refrigerators and air-conditioning units, and their use is poised to grow in the coming decades.

In the new study, a team led by Guus Velders at the Netherlands Environmental Assessment Agency in Bilthoven analysed the latest industry trends and then modelled HFC production to 2050. Their results suggest that HFC emissions could be the equivalent of between 5.5 billion and 8.8 billion tonnes of carbon dioxide annually by 2010 — roughly 19% of the projected CO 2 emissions if greenhouse gases continue to rise unchecked (G. J. M. Velders et al. Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0902817106 2009).

The new numbers will fuel the efforts of environmentalists and others who have been pushing for aggressive new HFC regulations. Manufacturers could shift towards using HFCs with the lowest climate impact during the transition to a new generation of refrigerants — still under development — that affect neither the ozone layer nor the climate.

"Now is the moment to make a decision to steer this in a direction that you want," Velders says. "The developing world is already in the transition to HFCs."

Although it makes no policy recommendations, the study could play into an ongoing political debate on regulating the chemicals. HFCs currently fall under the umbrella of the Kyoto Protocol on climate change, but advocates say the fastest and cheapest way to handle them is under the ozone treaty. Montreal delegates plan to discuss the issue when they meet in Geneva next month.

“Now is the moment to make a decision to steer this in a direction that you want.” Guus Velders

Netherlands Environmental Assessment Agency

Durwood Zaelke, who heads the advocacy group Institute for Governance and Sustainable Development in Washington DC, says the Velders study confirms the potential benefits of regulating HFCs under the Montreal agreement. It will, he says, help build momentum as the delegates move towards a decision in November.

The Montreal treaty, which came into force in 1989, has implementation experts in virtually every country and has already succeeded in reducing 96 chemicals by 97% each, Zaelke says. "It's a winning record, and we need to give the treaty this shot."

In 2007, Velders' team looked at the effect of the Montreal Protocol and found that its incidental greenhouse-gas reductions — equivalent to 11 billion tonnes of CO 2 annually by 2010 — are five to six times greater than those of the Kyoto Protocol. Montreal participants had already agreed to phase out chlorofluorocarbons by 2010 and hydrochlorofluorocarbons by 2040, but the Velders study helped convince them to accelerate phasing out the latter by a decade in order to capture the climate benefits.

The latest study carries that work forward and suggests that the problem posed by HFCs could be several times larger than projected by the Intergovernmental Panel on Climate Change (IPCC) in its 2007 assessment. Using the IPCC's baseline economic scenarios, the work assumes that refrigerant technologies will be deployed at levels roughly equal to those in the developed world today. By mid-century, emissions in currently developing countries would rise to levels eight times higher than those in developed nations.

Venkatachalam Ramaswamy, a coordinating lead author of the IPCC chapter covering HFCs who was not involved in the study, called the paper "a very good piece of work".

"It elevates the importance of HFCs in terms of climate forcing to a level higher than we may have thought initially," says Ramaswamy, a scientist at the National Oceanic and Atmospheric Adminstration's Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey.

Still, he says, it "doesn't significantly detract from the attention that CO 2 and methane should be getting."