One of the advantages of the Tardis is that it allows going back in time and ignoring the present or even the more recent past. This really is an advantage when you are pretending that the last word on proxy reconstructions of climate is Mann, Bradley and Hughes 1998 like Aunt Judy in the Climate Etc attic or Steve McIntyre reliving past cherry picks. Willard Tony does a nice jig on ozone republishing on Watts Up what he bleated over at PJMedia (are they still alive?). There is much to giggle about in WT's attempt to appear profound, Sou is on the case, but allow Eli to start from near the end.
Eli, being a fair bunny, can quote WT
Or does it? Adding to the madness, now there is scientific uncertainty about the actual extent of the ozone problem as it relates to CFCs. More recent science has shown that the sensitivity of the Earth’s ozone layer might very well be 10 times less than was originally believed back in the 1980s when the alarm was first sounded. As reported in the prestigious science journal Nature, Markus Rex, an atmospheric scientist at the Alfred Wegener Institute for Polar and Marine Research in Potsdam, Germany, found that the breakdown rate of a crucial CFC-related molecule, dichlorine peroxide (Cl2O2), is almost an order of magnitude lower than the currently accepted rate:
“This must have far-reaching consequences,” Rex says. “If the measurements are correct we can basically no longer say we understand how ozone holes come into being.” What effect the results have on projections of the speed or extent of ozone depletion remains unclear.before, well, before. That link goes back to 2007, almost a pause ago, and is not to a scientific paper, but a news report, one which quotes Rex. What this is all about is a claim by Pope et al from JPL that the absorption cross-section of ClO-OCl (aka the ClO dimer or Cl2O2) was much smaller than had previously been measured. This would mean that the rate at which broke apart (photolyzed or photodissociated) after absorbing a UV photon was much slower. Thus there would be much less ClO and Cl available to participate in the catalytic destruction of ozone.
ClOOCl + hv --> Cl + ClOOTo understand how
ClOO + M --> Cl + O2+M
and two of the Cl atoms react with two ozone molecules
Cl + O3 --> ClO + O2
Other groups have yet to confirm the new photolysis rate, but the conundrum is already causing much debate and uncertainty in the ozone research community. “Our understanding of chloride chemistry has really been blown apart,” says John Crowley, an ozone researcher at the Max Planck Institute of Chemistry in Mainz, Germany.and of course, some of the debate and uncertainty lead to new experimental measurement, but that takes a while, and a short while longer to get published. In 2009, Eli commented on a paper from the Academica Sinica in Taiwan that conclusively showed Pope et al to be wrong. Of course there was more, most importantly a paper by Burkholder's group (Papanastasiou, et al) at the NOAA Boulder lab (open version sort of).
The UV photolysis of Cl2O2 (dichlorineperoxide) is a key step in the catalytic destruction of polar stratospheric ozone. In this study, the gas-phase UV absorption spectrum of Cl2O2 was measured using diode array spectroscopy and absolute cross sections, σ, are reported for the wavelength range 200-420 nm. Pulsed laser photolysis of Cl2O at 248 nm or Cl2/Cl2O mixtures at 351 nm at low temperature (200-228 K) and high pressure (∼700 Torr, He) was used to produce ClO radicals and subsequently Cl2O2 via the termolecular ClO self-reaction. The Cl2O2 spectrum was obtained from spectra recorded following the completion of the gas phase ClO radical chemistry. The spectral analysis used observed isosbestic points at 271, 312.9, and 408.5 nm combined with reaction stoichiometry and chlorine mass balance to determine the Cl2O2 spectrum. The where the quoted error limits are 2σ and include estimated systematic errors. The Cl2O2 absorption cross sections obtained for wavelengths in the range 300-420 nm are in good agreement with the Cl2O2 spectrum reported previously by Burkholder et al. (J. Phys. Chem. A 1990, 94, 687) and significantly higher than the values reported by Pope et al. (J. Phys. Chem. A 2007, 1, 4322). A possible explanation for the discrepancy in the Cl2O2 cross section values with the Pope et al. study is discussed. Representative,atmospheric photolysis rate coefficients are calculated and a range of uncertainty estimated based on the determination of σCl2O2(λ) in this work. Although improvements in our fundamental understanding of the photochemistry of Cl2O2 are still desired, this work indicates that major revisions in current atmospheric chemical mechanisms are not required to simulate observed polar ozone depletion.And what is the possible problem with the Pope study, well, turns out that they were measuring the absorption of ClO dimer in the same region where Cl2 absorbs (btw 300 and 400 nm, kind of bell shaped). As the abstract discusses, the method of production ClO dimer also produces Cl2 as a by product, and thus you have to know how much Cl2 there is in the mixture you are measuring. Papanastasiou, et al think that Pope et al got this slightly wrong (4.5%).
Also in 2009, there was a nice paper by the Anderson group at Harvard showing that the amount of Cl produced in the photolysis of ClOOCl was exactly what had been pre-Pope expected.
And finally, Pope, now at the University of Birmingham has a new paper (2013) extending the spectral measurements into the visible using cavity ring-down. Perhaps another post
Eli tried to be nice, pointing this out to WT's fans, but you know. . .