For decades, scientists assumed the Earth’s ozone layer was on the mend after the adoption of the Montreal Protocol, but a new study casts doubt on that long-held assumption.
A team of international scientists have found that while upper stratospheric ozone is recovering, “the continuing downward trend in the lower stratosphere prevails, resulting in a downward trend in stratospheric column ozone,” outside the polar regions.
Basically, ozone levels in the lower stratosphere have slightly decreased since 1998 that can’t be explained by scientific models. In fact, scientists really aren’t sure why lower stratospheric ozone has defied their predictions.
“We find that total column ozone [outside the poles] appears not to have decreased only because of increases in tropospheric column ozone that compensate for the stratospheric decreases,” the scientists wrote in their study.
“The reasons for the continued reduction of lower stratospheric ozone are not clear; models do not reproduce these trends, and thus the causes now urgently need to be established,” scientists wrote.
Scientists aren’t really sure why lower stratospheric ozone is not mending like they expected. One scientist suggested it could be due to a change in “stratospheric circulation, which has a large influence on how ozone is distributed,” they told The Washington Post.
It could also be due to an ozone-depleting chemical not covered by the Montreal Protocol, which was adopted in 1987 amid the hype over the “hole” in the ozone layer above Antarctica. The Protocol forces countries to phase out ozone-depleting chemicals.
Another scientist told WaPo it could be related to man-made global warming, but again, scientists have no idea what’s really going on.
“At the moment, there’s no proof of what’s causing it but there are some reasonable hypotheses that need to be investigated,” study lead author William Ball, a Swiss scientist, told WaPo. “We’re raising the alarm that we need to very rapidly investigate whether it’s the short-lived compounds, whether it’s a climate change response, whether our models aren’t quite doing the right job, or whether there’s something wrong with the data.”
Late last year, NASA reported the ozone “hole” over Antarctica was the smallest on record due to “natural variability,” not the Montreal Protocol. The small ozone “hole” extent was “not a signal of rapid healing,” NASA scientists found.
The ozone hole over Antarctica “forms during the Southern Hemisphere’s late winter as the returning sun’s rays catalyze reactions involving man-made, chemically active forms of chlorine and bromine,” according to NASA.
The Earth’s ozone layer “acts like sunscreen, shielding the planet from potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and also damage plant,” NASA said.
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