World's longest ozone record
.... and inferred UV changes
In the just-published annual report from the the World Radiation Data Centre in Davos, Switzerland I came across a nice plot showing the time series of ozone data reaching right back to the 1920s when the Dobson instrument to measure ozone was first developed. Coincidentally, my office at Oxford in the 1980s, on the roof of the atmospheric physics laboratory, was called the ‘Dobson Hut’. It was the very place where he first developed the instrument. That earliest version of the instrument used less accurate photographic plates rather than the current electronic detectors, which became available in the 1950s.
The ozone time series is from the Arosa mountain observatory, just across the ‘hill” from Davos. It’s the longest on record, so therefore provide the longest context for the reductions due to CFCs late last century, and its satibilisation and beginnings of recovery since then.
The plot makes it clear that
we had an unprecedented problem with ozone starting around 1980 (due to increasing chlorine from CFC), and
it bottomed out around the turn of the century (due to the success of the Montreal Protocol), and
it’s now improving, but only slowly (due the the long atmospheric lifetimes of CFCs).
Without the Montreal Protocol, that steep downward trajectory over the period 1980 to 2000 would have continued unabated, with ozone reductions of 50 percent or more by the second half of this century leading to more than a doubling of skin-damaging UV radiation.
Luckily, thanks to the Montreal Protocol, that won’t happen.
At this Swiss site, the maximum ozone reduction was about 5 percent, which would have led to an increase in sunburning UV of around 6 percent. Assuming no changes in aerosol extinctions at this unpolluted site, current UV clear-sky levels should be no more than 5 percent greater than at any time in the last hundred years. Results would be similar at other unpolluted sites, which raises doubt about anecdotal remarks I sometimes hear about “the UV feeling much stronger these days”. That’s clearly more of an awareness issue than a true physiological effect.