Thursday, 20 September, 2018

Banned Ozone-Harming Gas Creeps Back, Suggesting a Mystery Source

Beijing is shrouded with smog Beijing is shrouded with smog
Theresa Hayes | 17 May, 2018, 04:00

Emissions of one of the chemicals most responsible for the Antarctic ozone hole are on the rise, despite an worldwide treaty that required an end to its production in 2010, a new NOAA study shows. Global production of CFC-11, which has been used as a refrigerant and in insulating foams, has been banned since 2010 under the Montreal Protocol. The source of the new emissions has been tracked to east Asia, but finding a more precise location requires further investigation.

However, it took many decades for scientists to discover that when CFCs break down in the atmosphere, they release chlorine atoms that are able to rapidly destroy ozone molecules.

Nearly no CFC-11 has been been produced since 2006 - or so we thought.

"We're raising a flag to the global community to say, 'This is what's going on, and it is taking us away from timely recovery from ozone depletion, '" said NOAA scientist Stephen Montzka, lead author of the paper, which has co-authors from CIRES, the United Kingdom, and the Netherlands. The growth in the size of the ozone "hole" over Antarctica has slowed.

The UNEP said that is was "critical that we take stock of this science, identify the causes of these emissions and take necessary action".

The study authors point out that while CFC-11 can persist in the atmosphere for 50 years, the overall level of chlorine atoms is still declining. Rather, the evidence "strongly suggests" a new source of emissions, the scientists wrote. Then, surprisingly, the rate of decline hardly changed over the decade that followed.

The new study published on Wednesday shows that, as expected, the rate of decline of concentrations of CFC-11 observed was constant between 2002 and 2012.

It is possible that the increased emissions could be due to older buildings being demolished, but that doesn't seem to be the case.

Measurements from Hawaii indicate the sources of the increasing emissions are likely in eastern Asia.

A sharp and mysterious rise in emissions of a key ozone-destroying chemical has been detected by scientists, despite its production being banned around the world.

Montzka said the world's nations are committed to its enforcement.

The USA ceased production in 1996 and other countries agreed to phase out CFC production by 2010.

As a result of the controls, CFC11 concentrations have declined by 15% from peak levels measured in 1993.

That has led scientists to predict that by mid- to late-century, the abundance of ozone-depleting gases would to fall to levels last seen before the Antarctic ozone hole began to appear in the early 1980s. "This suggests unreported new production".

Erik Solheim, head of UN Environment, said: "If these emissions continue unabated, they have the potential to slow down the recovery of the ozone layer".

"This is the first time that emissions of one of the three most abundant, long-lived CFCs have increased for a sustained period since production controls took effect in the 1980s", the study concluded.

The ozone layer is slowly recovering, and ozone-depleting substances are still declining.

She said: "The study highlights that environmental regulations can not be taken for granted and must be safe-guarded, and that monitoring is required to ensure compliance".

The Montreal Protocol, signed by more than 200 countries and generally regarded as having a good record of compliance, is created to protect the Earth's ozone layer.