Thursday, August 15, 2013

Polluting the climate

There are a number of more or less feasible ways in which humans may influence climate, both locally and globally.

An interesting theory published by Professor Qing-Bin Lu back in May makes the claim that chlorofluorocarbons (CFCs) once widely used as refrigerants, cleansers, aerosol propellants and foam-blowing agents may have affected the climate as greenhouse gases as well as damaging the ozone layer.

The chemistry and physics behind CFC-induced ozone layer damage are fairly well established, although Professor Lu thinks the ozone-destroying reactions are initiated by cosmic rays rather than the usual explanation based on solar uv photolysis.

Whatever the initiating pathway to ozone damage, the Montreal Protocolcame into being in 1989 and appears to have been successful in controlling and reducing the use of CFCs linked to that damage.

However, Professor Lu claims that those same CFCs also warmed our climate because they happen to be powerful greenhouse gases.

Chlorofluorocarbons (CFCs) are to blame for global warming since the 1970s and not carbon dioxide, according to new research from the University of Waterloo published in the International Journal of Modern Physics B.

CFCs are already known to deplete ozone, but in-depth statistical analysis now shows that CFCs are also the key driver in global climate change, rather than carbon dioxide (CO2) emissions.

So we have yet another climate theory, but an interesting one because it seeks to account for both the late twentieth century warming from about 1970 to 2002 and also the recent warming hiatus from about 2002 to the present, data which the CO2 theory fails to explain. According to Professor Lu, as we phased out those CFCs, the warming stalled in spite of a continued rise in atmospheric CO2 concentrations.

Although the paper received some publicity at the time, such as here, here, here and here, it now appears to have sunk below the mainstream horizon. Which is a pity, because if nothing else Professor Lu’s work suggests we are some way from understanding basic climate drivers, let alone classifying them in order of importance.

In climate science, the elephant in the room is surely uncertainty.

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Sackerson said...

That IS interesting. I seem to recall from years ago that CFCs were said to particularly pernicious because they persisted at high altitude for a long time and also the chemical reaction was repeated, i.e. each CFC molecule would interact with one ozone molecule after another. Have I got that wrong?

A K Haart said...

Sackers - exactly - there are a series of catalytic reactions where one CFC molecule destroys many ozone molecules.

I think this may be where climate scientists acquired the notion of positive feedback, but the idea never made it beyond computer models into observable physics and chemistry.