Two of the options for dealing with global warming have run up against walls this week.
The cancellation of the development of the FutureGen clean coal power plant is the end of clean coal as an option for electricity generation.
Science carries a paper on the carbon costs of ethanol-as-fuel showing that this will increase emitted carbon. This surprising result is because ethanol crops force food crops into more marginal soils, and the benefits from ethanol can't make up for the addition carbon needed for the less efficient food production and distribution. Worse still, the falling efficiency of food production leads to starvation in some low income farming countries if biofuels are used within the US at the level at which fossil fuels are currently used.
None of this is happy news. Remaining viable options are: a radical reduction in the consumption of energy, solar, and nuclear (and it's unclear if nuclear will remain on the list, as there's been some scientific bastardry in studies of the carbon life cycle in nuclear power generation and we'll need to wait for GW Bush to leave office for the results). It also marks the end of the viability of the car. It's unlikely that this scale of social change in acheivable in the time required to avoid large environmentally-caused catastrophes.