A cap-and-trade on greenhouse emissions would do just that. It guarantees that emissions will be reduced by a specific amount by a specific date, and encourages innovation and savvy investment by rewarding the technologies that reduce the most emissions at the least cost.

The 2006 Assessment:

http://www.esrl.noaa.gov/csd/assessments/2006/chapters/twentyquestions.pdf

projects that the ozone hole will heal between 2060 and 2075, some 10-25 years later than projected in the 2002 Assessment. Moreover, the 2006 Assessment says it will be more than 20 years before we see a significant improvement.

This is an unfortunate illustration of the pitfalls of waiting too long to respond to warnings of an environmental crisis. If the world had acted in the 1970's when scientists first warned of the dangers of CFCs, we could have prevented all this. Now we're at serious risk of making the same mistake with the climate – and the consequences will be far greater.

I am glad to see that environmental defense is not advocating ethanol in these articles. As James Hansen of NASA points out, ethanol contibutes to global warming if used in cars. However, if used to generate electricity and the CO2 were to be sequestered in the process, this would actually decrease CO2 in the atmosphere and assist in the battle to head off global warming.

"It will take at least another 10 years or so for the hole to be gone completely."

Please check the 2006 World Meteorological Organization/United Nations Environment Programme Scientific Assessment of Ozone Depletion.

Climate change from CO2 pollution and destruction of the ozone layer are basically unrelated, but there is one way they do interact. Greenhouse gases like CO2 raise the temperature in the lower atmosphere, but lower it in the upper atmosphere or stratosphere, where the ozone layer is.

I know that sounds counterintuitive. Here's why it happens. Heat leaves the earth by radiating into space, and CO2 is one of the radiators. With higher CO2 concentrations, the altitude at which the CO2 radiates to space increases and this causes cooling and lower temperatures in the stratosphere.

The cooling in the stratosphere leads to the creation of more ice crystals. Since reactions that deplete the ozone occur on the surface of these ice crystals, higher CO2 concentrations can exacerbate ozone depletion.

By the way, while we're on the topic, the rate of increase in the ozone hole is slowing, in large part because of the international treaties that have banned to use of chlorofluorocarbons. It's hard to tell for sure because of year-to-year fluctuations, but it may even have started to decrease. It will take at least another 10 years or so for the hole to be gone completely.

Thanks,