one of the more "promising" geoengineering ideas out there—a proposal to inject sulfates into the air to mimic the cooling effect that was caused by the eruption of Mount Pinatubo in 1991—could end up obliterating the ozone layer in the Arctic (which would, in turn, affect large swaths of the Northern Hemisphere; since the ozone shields us from cosmic radiation and whatnot, this would be a rather suboptimal outcome). This comes on the heels of an earlier study suggesting that the sulfate plan would wreak havoc on global rainfall patterns.Note that the rainfall point isn't theoretical: the droughts in the Sahel throughout the 70s and 1980s (remember "We are the world"?) are now traced directly to the sulphur emissions from developed countries.
Still, it would be a boon for sunblock manufacturers! Why don't we report the good news about climate change!
2) This summer -- 2008, this year, a few months from now -- might see open water clear to the North Pole. (Not necessarily an ice-free Arctic Ocean, but even worse than last summer.) Worth repeating: open water absorbs much, much more heat than ice, so arctic warming represents a massive "tipping point" in climate change. Also, leaving Greenland as an island of ice in an ocean of open rapidly warming water is not a strategy for success.
3) The warming of the Arctic is probably responsible for a large increase in concentrations of methane -- a greenhouse gas 25x more potent than CO2 -- that has reversed the temporary decline we saw begin after 2000. Methane in the atmosphere eventually turns in to CO2, and then it stays in the atmosphere more or less "forever", ie for centuries.
It looks more and more (to me, anyway) like the point at which moderate human action could have averted damaging climate change is behind us. The objective now is to avoid global calamity.