Ken Caldeira has posted in favor of one of the few suggestions I hear about global warming that sounds like a cost-effective approach to controlling the climate. His idea is to put sulfate particles into the atmosphere to reverse the greenhouse effect and cool the planet down. The idea is attractive because it has effects within months, and because small numbers of people can make it happen. To contrast, reducing CO2 emissions takes global cooperation, is very expensive, and takes decades to have any effect.
I would count this idea as serious about global warming.
There is some good discussion on Megan McCardle's blog. Arnold Kling, ever the economist, sees uncertainty and thinks of insurance, and so likes the just-in-case aspect of this approach.