To curb climate change, looking beyond carbon dioxide to your AC
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Even as global temperatures shatter records in 2016, the year's biggest opportunity to curb further warming hinges on little-noticed negotiations addressing little-known chemicals.

International negotiations in Vienna last month neared a deal for curtailing hydrofluorocarbons (HFCs). These refrigerants substitute for ozone-destroying chlorofluorocarbons (CFCs) in air conditioners and refrigerators.

Since HFCs don't contain chlorine, they don't destroy ozone. Replacing CFCs under the Montreal Protocol is already helping to heal the ozone layer. Scientists expect the ozone layer will recover to natural levels over the next few decades.

Despite their ozone benefits, HFCs are greenhouse gases, too. This may not seem like a weighty matter for climate: Global emissions of HFCs are about 30,000 times less than those for carbon dioxide. That's roughly the ratio between a pygmy mouse and a lion.

But pound for pound, HFCs cause over 1,000 times as much warming as carbon dioxide. That's not quite as potent as CFCs, but still a major concern for climate.

HFCs play a small role in warming today. However, as air conditioning use grows, so too will emissions. Air conditioners are expected to become far more prevalent as consumers grow wealthier in hot climate countries like India. Worldwide, 1.6 billion air conditioners could be installed by 2050, dwarfing today's numbers.

Berkeley National Laboratory reports that more climate-friendly refrigerants coupled with more energy-efficient air conditioners could save the equivalent of 98 billion of carbon dioxide cumulatively by 2050. That's nearly three years worth of global emissions from fossil fuels.

No single substitute can replace HFCs in all products and weather conditions, and some options remain under development. Transitioning to alternative refrigerants could be costly at first.

Nevertheless, HFCs may prove easier to control than carbon dioxide. Whereas HFCs are used in a limited number of products, carbon dioxide-emitting fossil fuels provide over 80 percent of the world's energy. Reducing carbon dioxide emissions thus requires massive investments in energy efficiency and low-carbon energy sources throughout the energy economy. Fossil fuel producers may resist efforts to slash emissions quickly.

By contrast, the chemical industry could prove a powerful advocate for replacing HFCs. Companies like Dupont and Dow see opportunities to develop and sell the replacements for HFCs, much as they profited from replacing CFCs under the original Montreal Protocol. Industry and environmentalists could find common ground in promoting progress.

That's not to say we can ignore carbon dioxide, the leading cause of ongoing warming. Still, controlling HFCs can contribute to a comprehensive climate strategy.

Scientists predict that replacing HFCs with more climate-friendly alternatives could curb warming by 0.5 degrees Celsius (0.9 degrees Fahrenheit) by 2100. That's a lot, considering that the Paris Agreement aims to keep total warming below 2 degrees Celsius above pre-industrial levels. Temperatures in 2016 are already nearing the 1.5 degree Celsius threshold.

The Vienna talks did not reach a final agreement. However, the talks set the stage for the annual Montreal Protocol meeting in Kigali, Rwanda, in October. Negotiators there will aim to amend the ozone-saving protocol to enhance its benefits for climate.

coalition of 35 countries, including the United States, seeks ambitious measures to curtail HFCs. However, some other countries remain skeptical about how quickly they can transition to alternative refrigerants. Details remain unresolved about the timetables for phasing down HFC use. Nevertheless, negotiators in Vienna agreed to use the Montreal Protocol's Multilateral Fund to support developing countries in making the transition.

Headlines about climate policy will likely remain focused on the November U.S. presidential election and the annual United Nations climate conference in Morocco later that month. But don't be surprised if history shows the October meeting in Rwanda to be 2016's most consequential brake on ongoing warming.

Cohan is an associate professor in the Department of Civil and Environmental Engineering at Rice University.

The views expressed by contributors are their own and not the views of The Hill.