Sherwood Rowland, CFCs, ozone depletion and the public role of scientists

Many of you will have read the obituaries of the Nobel Prize-winning chemist Sherwood Rowland (Nature, BBC) who sadly died over the weekend. DotEarth has a good collection of links to papers, videos and tributes.

We have sometimes commented on the connections between the issue of CFC-driven ozone depletion and anthropogenic global warming. In both cases, there is a global atmospheric problem caused by specific emissions, that has a potential to be dangerous, for which the science provided strong evidence for (but never absolute proof), and for which observations ran ahead of predictions for many years. In the ozone case, this led to important preventative actions (via the Montreal Protocol and its amendments). There are of course links that go deeper than just analogies – ozone depletion itself has a small cooling effect, CFCs are important greenhouse gases, and prior to the Montreal protocol amendments, were a large component of the year on year increase in radiative forcing. Indeed, the Montreal Protocol has done more to reduce radiative forcing than any other climate mitigation measure – and it isn’t even a climate mitigation measure!

Going the other way, ozone depletion is a chemical process and is affected by temperatures and water vapour in the stratosphere. Ozone recovery in the tropical stratosphere is expected to be faster and the recovery of the polar ozone hole is expected to be slower because of the CO2-induced cooling of the stratosphere (and increase the number of polar stratospheric clouds). Another link is associated with the dynamical impact of the ozone hole around Antarctica increasing the westerly winds dramatically.

There are also links that are perceived in the broader public that are not actually true: CFCs are not aerosols (despite what the New York Times claims), global warming does not exist because of extra heat coming in through the ozone hole, and aerosol sprays do not cause global warming.

In the public debate, many of the climate contrarians (such as Fred Singer) got their start denying that CFCs were affecting ozone, using many of the same arguments they now use about climate change (CFCs are heavier than air! it’s all the sun! the science is uncertain! the scientists are KGB agents! any controls will cause untold misery in the developing world!), and for much the same reasons. But through this all, Sherry Rowland strode tall (literally – he was 6 ft 5 in), and played a large role in debunking some of the wild claims (such as the idea that it was all volcanoes).

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