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Atmospheric hole discovered

A rice farmer plants crops in a dried-up paddy in Kampong Speu’s Kong Pisei district in 2012
A rice farmer plants crops in a dried-up paddy in Kampong Speu’s Kong Pisei district in 2012. Scientists have discovered a large hole in the atmosphere’s lowest layer above Southeast Asia. Heng Chivoan

Atmospheric hole discovered

Scientists have discovered a new phenomenon in the skies above Southeast Asia: a huge, invisible hole in the atmosphere’s lowest layer that may exacerbate the effects of Cambodia’s climate change.

The hole – roughly twice the length of New Zealand and concentrated just east of the Philippines – is really an absence of what scientists call the “OH shield”, the atmosphere’s filtering, detergent layer that breaks down pollutants before they wreak havoc farther up.

Under normal circumstances, pollutants are reduced in the OH shield, absorbed by water vapour and washed out by rain. But with no OH shield, the polluting substances in the Western Pacific travel to higher altitudes where their ozone-depleting effect is amplified.

“You can imagine this region as a giant elevator to the stratosphere,” said Markus Rex, an atmospheric physicist who led the team of researchers from the Alfred Wegener Institute that discovered the hole.

Climatologists have known about the degradation of the ozone – the stratospheric layer that deflects dangerous ultraviolet radiation from the sun – since the 1980s, but the rate of depletion they’re seeing is faster than models predicted.

Rex and his research team set out to measure ozone levels in 2009, and years later, after hundreds of tests, confirmed the giant, natural OH hole.

“There are no indications that this is a recent development or has been caused by human activities. We believe this is a natural phenomenon that has been there for a long time,” Rex said.

While the hole in the atmosphere’s filtering system may not be human-caused, it is expected to exacerbate the anthropogenic forces of climate change, including rising air pollution levels in the region.

“It’s obvious that these chemicals have an effect on climate change and there will be impacts to Southeast Asia, we just don’t know exactly what those changes will be yet,” Rex said.

Experts say it’s too early to take mitigation measures.

“It normally takes a few years from scientific discovery, to understanding the causes, to identifying solutions,” said Napoleon Navarro, deputy country director at the UNDP Cambodia.

To start piecing together how the OH hole will fit into the climate-change puzzle, the EU is funding a $12.5 million “Strato-Clim” monitoring centre. Meanwhile, scientists are predicting worldwide repercussions.

“If the emissions are transported up to the stratosphere . . . they have the potential to not only have impacts in Southeast Asia and Cambodia, but globally as well,” said Erika von Schneidemesser, an atmospheric research scientist at the German-based Institute for Advanced Sustainability Studies.

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