A new study published today by the National Academy of Sciences confirms unequivocally that a class of gases, whose use is expected to skyrocket in the developing world as living standards improve, poses an unforeseen and potentially grave threat by worsening global warming.
These "super greenhouse gases" known as hydrofluorocarbons, or HFCs, were originally developed to replace the use of ozone-depleting aerosols and are now commonly found in refrigerators, air conditioners and automobile cooling systems. If left unchecked, their build-up in the atmosphere could negate current efforts to reduce carbon dioxide to safe levels by 2050.
This emergency within the climate emergency has largely escaped public notice, but the new study is expected to raise its profile.
“You could undo the work on CO2 if you don’t do something about HFCs,” said Mack McFarland, a co-author of the paper and chief atmospheric scientist of Dupont, a leading HFC manufacturer. "I wouldn't call it an emergency but an opportunity."
In developing nations, use of HFCs is expected to increase 800% more than in developed nations, according to the study. The gases will find their way into billions of individual products whose disposal cannot be controlled, and will accumulate in the atmosphere, adding to the "radiative forcing" – or warming – of the climate.
Each molecule of these super GHGs has a global warming potential (GWP) many thousands of times greater than a molecule of CO2. HFC 134a, for example, is used in automobile air conditioning systems and has a global warming potential 1,430 times greater than CO2.
"The contribution of these chemicals to global warming will be much larger than we thought," said Guus Velders of the Netherlands Environmental Assessment Agency, the lead author of the study, who spoke to SolveClimate in advance of the publication.
"If left unchecked, HFCs would be the same as all the passenger cars in the world, times three. It's an unexpected finding, and it would be good to pay attention."
The study has a straightforward and unambiguous title: “The Large Contribution of Projected HFC Emissions to Future Climate Forcing.” Submitted for peer-review last March, it is being published today in the Proceedings of the National Academy of Sciences. The paper collected data from various sources: sampling of atmospheric concentrations, mandatory reports provided under the Montreal Protocol, and industry reports of production levels.
The data indicate that HFC emissions are expected to increase strongly within the next five years and contribute up to 170 gigatons of CO2 equivalent to the atmosphere by 2050. In 2050 alone, global HFC emissions are projected to be between 5.5 and 8.8 gigatons of CO2 equivalent. Current total U.S. CO2 emissions are about 7 gigatons.
“Our worst fears about HFCs have been validated,” said Sam LaBudde, a director at the non-governmental Environmental Investigation Agency. "We have to take care of HFCs to make the work being done on CO2 mean anything."
The warming effect of HFCs is most pronounced within the first 15 to 30 years of their release into the atmosphere. In a world where GHG concentrations are kept to 450 part per million – a target written into the Waxman-Markey climate legislation working its way through Congress – HFCs could account for almost half of global GHG emissions by 2050, according to the study.
"And it would continue to grow in an unconstrained scenario," McFarland of Dupont said. McFarland and his co-authors examined different scenarios in the study for phasing down use of HFCs. Their calculations showed that attacking the problem segment by segment or through U.S. legislation with only a regional effect would have little impact on the problem.
"We need to be looking at a global agreement, because the projected growth is primarily in developing countries," he said.
The study considered a scenario in which HFC use is frozen in 2014 in developed countries, frozen in developing countries in 2024, and subsequently decreased 4% a year until global use is curtailed 80%, and found it to be the most effective mitigation solution considered.
The 10-year gap between freezing use in developed and developing nations is a well-accepted phase down attribute of the Montreal Protocol, a highly successful treaty, now 20 years old, that has rid the world of more than 90 similar, dangerous gases.
The new study adds pressure upon the U.S. to show promised leadership on climate change. In April, the Federated States of Micronesia and Mauritius, two small island nations, proposed an amendment to the Montreal Protocol to allow the proven treaty to handle the phase down of HFCs.
Industry, NGOs and various U.S. agencies, including the State Department, were poised to join the effort to handle HFCs via the Montreal treaty, but the proposal has met invisible and unspoken resistance at the White House.