Earth Day optimism?

John Tierney of the NY Times tries to be optimistic for Earth Day:

I’ll make a couple of predictions:
1. There will be no green revolution in energy or anything else... and that, believe it or not, is good news, because...
2. The richer everyone gets, the greener the planet will be in the long run.

I am reminded of John Maynard Keynes's assertion that "in the long run we are all dead."

Tierney argues that our experience with local air pollution (which got worse in the U.S. but for the last few decades has been getting better) shows what will happen with global air pollutants like carbon dioxide. Unfortunately I don't think the analogy holds: it's more likely that we'll continue to clean up local pollutants without addressing global problems.

And Tierney---who quotes economist Jesse Ausubel as saying that economic forces will drive "most of the carbon [out of our energy system] by 2060 or 2070"---appears to be unaware of similar projections made in the past by fellow optimists like Bjorn Lomborg:

[R]enewable sources such as wind and solar energy are decreasing rapidly in price... Thus, it seems plausible that renewable energy will by itself or with fairly little “nudging” be competitive before mid-century. [The Skeptical Environmentalist (2001), p285]

The truth is that there is no economic reason that renewable energy is destined to become cheaper than coal, and the low marginal costs of running a coal plant suggests that the ones we're building today will (in the absence of a carbon tax or other government policy) stay in operation for decades.

But to honor Tierney's optimism I propose that we christen the Tierney unit (a la the Friedman unit) as the 3-5 decade period in which renewable energy will magically become cheaper than coal.