Clyde Burnett, Boulder County.  Solar short wavelength ultraviolet photons with energy proportional to frequency are capable of producing sunburn, which sometimes results in skin cancer. It can also produce an atmospheric chemistry reaction on volatile organic compounds (voc), like gasoline vapor and methane. Further reactions can then yield tropospheric ozone: a greenhouse gas that is dangerous to breathe.

The stratospheric ozone layer at an altitude of about 25 km absorbs solar ultraviolet, protecting us from much of the dangers. A recent scientific assessment of ozone depletion indicates northern hemisphere ozone layer loss from CFC’s since 1980 to be about 3%. The seasonal variation of the ozone layer shows a minimum from spring to early fall. This is also the season of high sun which means the path of sunlight is shorter through the absorbing protective layer. This is a good time for a reminder about sunburn: avoid exposure more than 15 minutes during the 2 hours before and after high noon (11-3) or use protective lotion renewed every 2 hours. The sky is blue due to short wavelength scattering by air molecules. This means that exposure to open blue sky, like time on the beach or open boat fishing, adds considerable ultraviolet in addition to direct and reflected sunlight. (No problem near sunrise and sunset.)

Ultraviolet reactions with gasoline vapor or natural gas that make tropospheric ozone can be avoided by not doing the following near midday: mowing the lawn with gas powered mowers, filling the auto gas tank, or ignoring natural gas (methane) leaks. This ozone is very bad to breathe, especially for individuals with asthma. Its additional infrared absorption capability is a concern because it adds greenhouse effect at the edge of the atmospheric window where there are no absorptions by other greenhouse gases.

Question: Our Secretary of Energy says the ocean, not CO2, is responsible for climate change. What’s wrong with that?

Answer: He has a little learning; that’s dangerous. It is typical sound bite science. Fact: Warmed water yields water vapor from evaporation. Next fact: water vapor absorbs infrared radiation from the Earth and traps heat. Return to fact one and repeat! And repeat! And repeat! This is called water feedback. Next fact: We have a thick layer of water vapor that is responsible for most of the global warming. Next fact. We have atmospheric circulation that moves this water vapor to a cooler region where it condenses. Next fact: the water runs back into the ocean; we have a complete water cycle with a period of about 10 days and a stable warm climate.

Question: How does CO2 add to the story and yield climate change?

Answer: CO2 is a trace constituent produced naturally by volcanoes, forest fires, and mammalian respiration. This molecule also absorbs infrared radiation, so it behaves just like water vapor by independently trapping heat in the atmosphere; the effect is small with such a few molecules. There is then just a slight additional warming of the ocean; that huge ocean furnishes extra water vapor to resume the water feedback and we have a little extra warming and a stable climate. When humans burn fossil fuel for energy, the CO2 perturbation won’t get corrected for a century and when we continue this year after year at an increasing rate, we have climate change. It was Penn State’s Professor Alley who described this as a control knob on the thermostat for heat trapping by water vapor.