Singer wrote in 1995,
<< For the general public, and even for the trained scientist, these scientific controversies are difficult to sort out. It is indeed a multi-faceted problem, a chain with many links connecting the release of CFCs into the atmosphere with the occurrence of skin cancer. Briefly, the steps are postulated as follows (6):
1. CFCs with lifetimes of decades and longer become well-mixed in the atmosphere, percolate into the stratosphere, and there release chlorine.
2. Chlorine, in its active form, can destroy ozone catalytically and thereby lower its total amount in the stratosphere.
3. A reduced level of ozone results in an increased level of solar ultraviolet radiation reaching the surface of the earth.
4. Exposure to increased UV leads to increases in skin cancer.
Each of these four steps is controversial, has not been sufficiently substantiated, and may even be incorrect (7,8). One can reasonably conclude that policy is rushing far ahead of the science. >>
William Connolley is picking apart #1 above (the well-mixed point).
The context of the discussion is the POLITICAL controversy over the CFC ban. Singer says it's not justified, because NOT ALL of the 4 points in the chain of reasoning are correct. If even one is incorrect, he argues, then the Montreal Protocol was unjustified.
It's basically Singer's POV vs. Connolley's POV. Lots of environmentalsts side with Connolley, and lots of others side with Singer.
Many of the environmentalists try to bolster their argument by saying that "the consensus of scientists" agrees with them. But I don't think Wikipedia ought to support the claim that such a "consensus" exists.
Now if someone did a survey, and 95% of scientists agreed on a point, we could arguably call that a "consensus" (as we have done on evolution: 95% of all scientists (not just biologist) surveyed support Darwin's theory, and well over 99% of biologists.
I'm getting tired, so I'll see you guys tomorrow...
Uncle Ed