01 August 2007

Our old friend Ozone

Ozone (O3) is a trace component in our atmosphere. It is a largely transient substance, with molecules being both created and destroyed mainly by the light of the Sun. Its presence is beneficial in the stratosphere, where it acts to absorb short-wavelength EM radiation. Nearer the surface, the photolysis of the gases (NOX) --in among other things, automobile exhaust -- allows for the production of tropospheric ozone, which typically results in range of health issues, particularly for those with respiratory problems. It is also a greenhouse gas, to boot.

Given this, we generally try to prevent the depletion of stratospheric ozone, while trying to suppress the creation of tropospheric ozone. As a result of climate change, those things may become more difficult.

...projections of increasing ozone near the Earth's surface could lead to significant reductions in regional plant production and crop yields. Surface ozone also damages plants, affecting their ability to soak up carbon dioxide from the atmosphere and accelerating global warming.

This is a pretty good example of a secondary effect and of a positive feedback. Something unintended come back to bite, and make things worse at the same time. However, with the following item, the relation to and the impact from climate change isn't as clear at this time.

Large quantities of ozone-depleting chemicals have been discovered in the Antarctic atmosphere by researchers from the University of Leeds...[finding] found high concentrations of halogens - bromine and iodine oxides -- which persist throughout the period when there is sunlight in Antarctica (August through May).


"Halogens in the lowest part of the atmosphere have important impacts on ozone depletion, the ability of the atmosphere to remove potentially harmful compounds, and aerosol formation. All these atmospheric phenomena are linked to climate change. We still have to work out what the ramifications of this discovery are. These exciting results also show how important it is to keep exploring the atmosphere - there seems to be plenty more to find out."

It is not clear to me that any real impact has been measured, only that it is a possible impact. Still, it is good to know beforehand, rather than finding out too late.

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