Dear Dr. Hansen:
An old engineer's dictum says "fast, cheap, good: pick two." Unfortunately, and I'm sure completely contrary to your intention, your solution to global warming favors "cheap" over fast.
Energy efficiency, renewable energies, and a "smart grid" deserve first priority in our effort to reduce carbon emissions. With a rising carbon price, renewable energy can perhaps handle all of our needs. However, most experts believe that making such presumption probably would leave us in 25 years with still a large contingent of coal-fired power plants worldwide. Such a result would be disastrous for the planet, humanity, and nature.
Fourth generation nuclear power (4th GNP) and coal-fired power plants with carbon capture and sequestration (CCS) at present are the best candidates to provide large baseload nearly carbon-free power (in case renewable energies cannot do the entire job).
OK, this begs the question of why depending on efficiency, carbon negative forestry and agriculture, and renewables would leave us "in 25 years with still a large contingent of coal-fired power plants worldwide."
We certainly have the physical capacity to build wind and solar generators that could provide all our power. Archer and Jacobson, perhaps the world's leading experts on wind potential, estimate that wind energy at 80 meters in commercially developable sites alone could could supply [PDF] five times the world's current energy demand. Note the emphasis: That is not five times world's current electricity consumption, but five times total world energy consumption, including cars and factories and non-electric heating1. Similarly, solar thermal power plants of the type already running in U.S. deserts2 can provide the world's entire energy needs [PDF] from less than 1 percent of total desert land3. Those are only two possibilities, albeit the ones with the biggest potential with today's technology.
