Emissions of a super-potent greenhouse gas have rocketed to record levels, despite previous reports that emissions of the gas had been almost eliminated over the past couple of years. The source of the emissions remains unclear, but it’s suspected that India and China could be responsible.

Reported in the journal Nature Communications this week, HFC-23 emissions are currently “higher than at any point in history,” despite some of the main producers suggesting their emissions had been cut. If the HFC-23 emissions reductions were as large as reported, the new study estimates that the equivalent of a year’s worth of Spain’s CO2 emissions would have been avoided between 2015 and 2017.

HFC-23 is a hydrofluorocarbon (HFC) gas that’s mainly produced as an unwanted by-product during the manufacture of a refrigerant used in air conditioners called HCFC-22. It’s one of the most potent greenhouse gases on the planet, with 1 tonne of its emissions being equivalent to the release of more than 12,000 tonnes of carbon dioxide. To make matters worse, it can persist in the atmosphere for much longer than other greenhouse gases too.

In 2016, world powers signed the Kigali Amendment to the Montreal Protocol to bring about a global phasedown of hydrofluorocarbons (HFCs), whose emissions had recently crept up in response to their use as replacements to ozone-depleting substances. While China and India are not yet bound by the Amendment, they announced ambitious plans to slash emissions in factories that produce the gas in 2015.

In light of this, scientists were hoping to see global emissions drop by almost 90 percent between 2015 and 2017. However, this was not the case.

“Although China and India are not yet bound by the Amendment, their reported abatement would have put them on course to be consistent with Kigali. However, it looks like there is still work to do. Our study finds that it is very likely that China has not been as successful in reducing HFC-23 emissions as reported," Dr Kieran Stanley, the lead author of the study and visiting research fellow at the University of Bristol’s School of Chemistry, said in a statement.

So, why is there such a big gap between the reported figures and the real figures? 

It’s hard to tell. While the study itself didn’t attempt to identify the source of the emissions, the Environmental Investigation Agency (EIA) argues that India and China are the likely culprits. They argue that China is by far the biggest producer of HCFC-22, so it’s likely they are also venting high levels of HFC-23 too. 

“It’s a climate crime of epic proportions,” Clare Perry, EIA Climate Campaigns Leader, said in a statement.

"This is yet another major blow to the stability of the planet’s climate. All possible sources of HFC-23 emissions need to be investigated and eliminated immediately,” added Perry.