A case in point concerns the claimed destruction of stratospheric ozone by long-lived chloride compounds derived from mass-produced chlorofluorocarbons, a theory that served as, and still remains, the basis for the international action plan of the Montreal Protocol. In March of this year, however, Pope et al. (2007), writing in The Journal of Physical Chemistry, described new measurements of the photolysis of chlorine peroxide, which comprises a key step in the destruction of polar stratospheric ozone. The new data indicated that photolysis rates may well be a factor of six lower than what had previously been believed to be the case, leading them to state that the large discrepancy "calls into question the completeness of present atmospheric models of polar ozone depletion."

In commenting on the findings of Pope et al., Markus Rex of the Alfred Wegener Institute of Polar and Marine Research in Potsdam, Germany, is quoted by Schiermeier (2007) as saying that if they are correct, "we can basically no longer say we understand how ozone holes come into being." By incorporating the new photolysis rate into a chemical model of ozone depletion, for example, he found that "at least 60% of ozone destruction at the poles seems to be due to an unknown mechanism."

So how are other ozone researchers reacting to these astounding observations?

Schiermeier quotes John Crowley of the Max Planck Institute of Chemistry in Mainz, Germany, as saying "our understanding of chloride chemistry has really been blown apart." Likewise, Neil Harris, who heads the European Ozone Research Coordinating Unit at the University of Cambridge is quoted as saying that "until recently everything looked like it fitted nicely," but that now "it's like a plank has been pulled out of a bridge," while John Pyle, also of the University of Cambridge, is quoted by Schiermeier as saying that he finds it "extremely hard to believe" that an unknown mechanism may be responsible for the bulk of observed ozone losses; but he does not deny that possibility.

Clearly, many people in the field are not dismissing out-of-hand the suggestion that the reigning polar stratospheric ozone depletion paradigm of the past two decades may be more wrong than right, which is a revealing reaction in light of all that has been done in the name of the theory. This is healthy and the way science should work. In addition, it suggests that some of that same open-mindedness should play a role in the debate over carbon dioxide and global warming. In fact, it should play an even greater role within the latter context, as earth's climate system is composed of many more phenomena than those that define polar stratospheric ozone concentrations.

On a closely related note, Markus Rex suggests, again quoting Schiermeier, that "even if the basic chemical model of ozone destruction is upheld, the temperature dependency of key reactions in the process could be very different -- or even opposite -- from thought." Likewise, even if the basic greenhouse effect of CO2 is correct, there are many feedback phenomena that could greatly alter its ultimate expression, both quantitatively and even qualitatively, as some pertinent processes are not true feedback phenomena dependent on an initial increase in temperature, but primary phenomena of a biological origin that (1) are directly driven by increasing atmospheric CO2 concentrations and that (2) have their own independent impact on climate, which often is to cool the planet.

So what will be the situation twenty years from now? We can only hope we will not be ruing the day back in 2007, or 8 or 9 or 10, when Al Gore and James Hansen convinced humanity that we already knew all we needed to know about carbon dioxide and global climate change to justify the draconian measures they succeeded in imposing upon us.

References
Pope, F.D., Hansen, J.C., Bayes, K.D., Friedl, R.R. and Sander, S.P. 2007. Ultraviolet absorption spectrum of chlorine peroxide, ClOOCl. Journal of Physical Chemistry A 111: 4322-4332.

Schiermeier, Q. 2007. Chemists poke holes in ozone theory. Nature 449: 382-383.