Scientists had expected fall in levels of HFC-23 after India and China said they had halted emissions

Efforts to reduce levels of one potent greenhouse gas appear to be failing, according to a study.

Scientists had expected to find a dramatic reduction in levels of the hydrofluorocarbon HFC-23 in the atmosphere after India and China, two of the main sources, reported in 2017 that they had almost completely eliminated emissions.

But a paper published in the journal Nature Communications says that by 2018 concentrations of the gas – used in fridges and air conditioners – had not fallen but were increasing at a record rate.

Matt Rigby, from Bristol University, who co-authored the study and is a member of the Advanced Global Atmospheric Gases Experiment, said academics had hoped to see a big reduction following the reports from India and China.

“This potent greenhouse gas has been growing rapidly in the atmosphere for decades now, and these reports suggested that the rise should have almost completely stopped in the space of two or three years. This would have been a big win for climate.”

Scientists say the fact they found emissions had risen is a puzzle and could have implications for the Montreal protocol, an international treaty that was designed to protect the stratospheric ozone layer.

Kieran Stanley, the lead author of the study, said that although China and India were not yet bound by the agreement, their reported reduction would have put them on course to be consistent with it.

“Our study finds that it is very likely that China has not been as successful in reducing HFC-23 emissions as reported,” he said. “However, without additional measurements, we can’t be sure whether India has been able to implement its abatement programme.”

HFCs were hailed as an answer to the hole in the ozone layer that appeared over Antarctica in the 1980s because they replaced hundreds of chemical substances widely used in aerosols that depleted the thin layer of ozone that protects Earth from harmful rays from the sun.

But in recent years there has been mounting concern at how the potent greenhouse gas was undermining efforts to keep global heating below dangerous levels. Scientists say one tonne of HFC-23 emissions is equivalent to the release of more than 12,000 tonnes of carbon dioxide.

Experts estimate that had the HFC-23 emissions reductions been as large as reported, the equivalent of a year’s worth of Spain’s CO 2 emissions would have been avoided between 2015 and 2017.

• This article was amended on 6 February 2020 because HFC-23 is not used in inhalers, as an earlier version wrongly said. This has been corrected.