Ross's 'Fly in the ointment'

Some good news among the bad ...

A paper recently published by Western et al. in Nature Geoscience shows that several supposedly banned CFCs have been increasing over the last decade.

Under the terms of the Montreal Protocol, the 5 chemicals shown have been all banned; but they may still be produced as feed-stock on the way to making the more ozone- and climate-friendly replacements. The figure below shows how they collectively contribute to ozone depletion (left panel) and climate change (right panel). The observed increase is mainly due to unwanted leakage emissions during that permitted use.

Results are shown in terms of their equivalence compared with CCF-11 (the main ozone depleting chemical) and CO2 (the main climate change chemical). The changes in the last decade look substantial.

Looks scary. But what’s not obvious from the plot is how the magnitude of those effects compare with the effects of CFC-11, the chemical they replace, on either Ozone Depletion or Climate Change. My colleague Ross Salawitch, who led the Twenty Questions and Answers Document that I talked about recently, was asked by the journal’s editor to write a comment on the paper.

In Ross’s commentary, he put the changes in context nicely with the plot below. His plot shows that while the ‘leakages’ from those 5 gases are a concern, and are significant, it’s not such a big deal overall (yet) either from an Ozone Depletion perspective (left plot below) or a Climate Change perspective (right plot below). In both cases, it’s less than 10 percent of the peak effect from CFC11s. As the concentrations of CFC-11 reduce, the relative importance of those 5 gases increases, but, at the present rate of change it will be a long time before their effects become important.