It might be useful to look to history.
Simplified story:
We've been in similar situations before. We started out burning trees for heat and to cook stuff. After a while, wood became scarce in many areas. Then, we stared burning coal for the same purpose.
Coal was also found to be a good source of energy for steam engines for transportation (steam ships and railroads).
Natural gas started being used for lighting and heat, and whale oil started being used for lubrication, make-up, and other things. But soon whale oil started becoming scarce. Cheap petroleum came on stream to help replace it.
As cities grew, people began to realize that the streets would soon be feet-deep in horse crap if some new way to get people and goods in and out for the millions who need them. Machines were needed to replace draft animals.
The point is that we know we've had to change our sources of energy over time for technological and scarcity reasons. We know that cheap petroleum and natural gas and even cheap coal will eventually be gone. We know there are consequences of using these fuels, and we know there are ways to power our societies without burning stuff. The future isn't destined to be cold and dark.
I think the smart thing to do now is invest in efficiency and to fund research and small scale development of a variety potential solutions. Taxing carbon-based fuel consumption, with a increasing bite over time, to help the fuels be priced at their true(r) cost would help. Making the tax refundable (as Hansen proposes) so that the poor and middle classes aren't further impoverished is important - we want people to make different choices, not get poorer. People aren't impoverished by doing 3 things on a car trip instead of two, or by driving a Honda Fit rather than a F-350.
I personally don't think that we have to attack climate change as vigorously as some - will the Earth really turn into Venus if we hit say 380 ppm versus 350 ppm CO2? Is the battle hopeless if we can't hit a particular number? I dunno. I think it's worth fighting the battle even if, at this time, we think that hitting a particular number seems too hard or too painful. What I think is most important is that we get started.
Yes, we should apply similar urgency to fighting malaria and cholera and political conflicts that threaten hundreds of millions right now. It doesn't have to be an either-or choice.
In short, I'm not quite so pessimistic. But I don't know the future either.
My $0.02.
Cheers,
Scott.
