Ozone Depletion May be Caused By Common Chemical Coolants

It turns out that common chemical coolants actually lead to ozone depletion. The coolants, known as hydrofluorocarbons (HFC), contribute by a small amount, which counters a decades-old assumption about them.

The ozone layer comprises a belt of ozone molecules located primarily in the lower stratosphere. It is responsible for absorbing most of the sun's harmful ultraviolet radiation before it reaches Earth's surface. Research in the 1990s showed that HFCs actually destroy a negligible amount of ozone. However, this was found by examining only the gases' ability to break down ozone molecules through chemical reactions that take place following the breakdown of these molecules in the atmosphere.

In this latest study, though, the researchers examined the five types of HFCs expected to contribute the most to global warming in 2050. The researchers found that the HFC emissions cause increased warming of the stratosphere, speeding up the chemical reactions that destroy ozone molecules. They also decrease ozone levels in the tropics by accelerating the upward movement of ozone-poor air. In fact, the impact is such that HFCs will cause a .035 percent decrease in ozone by 2050.

Of course, this contribution is small compared to predecessors. For example, trichlorofluoromethane causes about 400 times more ozone depletion per unit mass than HFCs. Even so, HFCs do provide a measureable contribution.

"What the paper demonstrates is that when you put this much of an infrared radiation-absorbing material in the stratosphere, even though it nominally does not destroy ozone in the same way that mainline ODSs [ozone-depleting substances] do, it's going to make a difference-it's going to start changing things," said Fahey, one of the researchers, in a news release. "It adds a new dimension of thinking that stratospheric scientists need to be aware of as they discuss these matters with policy makers."

The findings are published in the journal Geophysical Research Letters.

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