Reply #3: Positive feedbacks [View All]

[jpak]

Tropospheric greenhouse gases absorb upwelling IR that warms the stratosphere. Higher greenhouse gas concentrations in the troposphere cool the stratosphere.

Ozone also warms the stratosphere as well (it's a greenhouse gas).

Polar stratospheric clouds play a central role in the chemistry of stratospheric ozone depletion - they form at temperatures < -78 degrees C.

Deplete ozone and the stratosphere cools even further, which enhances the formation of polar stratospheric clouds, which enhances ozone depletion, which further cools the stratosphere, etc...

Upwelling methane is the primary source of water vapor in the stratosphere - it's photo-oxidized to CO2 and water. As more anthropogenic methane is supplied to the stratosphere, there is more water vapor available to form polar stratospheric clouds (PSC's) further enhancing the probability that ozone depletion will occur etc. etc.

If the Montreal Protocol is adhered to, however, anthropogenic halogens in the stratosphere will decline to insignificant levels in fifty years or so.

But in the meantime, there's going to be some nastiness to contend with...