Scientists fear ozone gas cheat

Emissions of a banned ozonedepleting chemical are on the rise, a group of scientists reported yesterday, suggesting someone may be secretly manufacturing the pollutant in violation of an international accord.

Emissions of CFC-11 have climbed 25 per cent since 2012, despite the chemical being part of a group of ozone pollutants that were phased out under the 1987 Montreal Protocol.

‘‘I’ve been making these measurements for more than 30 years and this is the most surprising thing I’ve seen,’’ said Stephen Montzka, a scientist with the National Oceanic and Atmospheric Administration, who led the work.

‘‘I was astounded by it really.’’ It’s a distressing result for what’s widely seen as a global environmental success story, in which nations – alarmed by a growing ‘‘ozone hole’’ – collectively took action to phase out chlorofluorocarbons.

The finding seems likely to prompt an international investigation into the mysterious source.

Officially, production of CFC11 is supposed to be at or near zero – at least, that is what countries have been telling the United Nations body that monitors and enforces the protocol.

But with emissions on the rise, scientists suspect someone is making the chemical in defiance of the ban.

‘‘Somebody’s cheating,’’ said Durwood Zaelke, founder of the Institute for Governance and Sustainable Development and an expert on the Montreal Protocol, in a comment on the new research.

‘‘There’s some slight possibility there’s an unintentional release, but ... they make it clear there’s strong evidence this is actually being produced.’’

But for now, the scientists don’t know exactly who, or where, that person would be.

A US observatory in Hawaii found CFC-11 mixed in with other gases that were characteristic of a source coming from somewhere in east Asia, but scientists could not narrow the source down any further.

Zaelke said he was surprised by the findings, not just because the chemical has long been banned, but also because alternatives already exist, making it hard to imagine what the market for CFC-11 today would be.

The research was led by researchers with the US National Oceanic and Atmospheric Ad- ministration with help from scientists in the Netherlands and the United Kingdom. Their results were published in the journal Nature.

There is a small chance that there is a more innocent explanation for the rise in CFC-11 emissions, the scientist say.

They considered a range of alternative explanations for the growth, such as a change in atmospheric patterns that gradually remove CFC gases in the stratosphere, an increase in the rate of demolition of buildings containing old residues of CFC-11, or accidental production.

But they concluded these sources could not explain the increase, which they calculated at about 13 billion grams per year in recent years.

Rather, the evidence ‘‘strongly suggests’’ a new source of emissions, the scientists wrote.

‘‘I’ve been making these measurements for more than 30 years and this is the most surprising thing I’ve seen.’’

Stephen Montzka, National Oceanic and Atmospheric Administration