Noted thinker and academic Vaclav Smil penned a lengthy critique of renewable energy this month titled “A Skeptic Looks at Alternative Energy.” Smil makes a number of points but the most important to my mind are: 1) As much as the U.S. and Europe do to shift to renewables, India and China are now the real problem in terms of growth of carbon emissions and 2) Subsidizing renewables long term is unsustainable unless everyone is willing to pay much more for energy which is improbable, particularly in the developing world.  Smil does a good job at pointing out how long it took to research, invest, and build infrastructure/networks for coal, nuclear and natural gas, often as long as 45 years in the case of natural gas. And there’s little reason to believe renewables won’t take at least that long. But where I disagree with Smil is around his assessment of the costs of fossil fuels. We assume their cost is just the spot price of the natural resource but there are hard economic costs to carbon emissions, which are admittedly much harder to model, but are still going to be real and should inform how we think about the price comparisons between fossil fuels and renewable energy.