[Editor’s note: When this post was originally run, the phrase “100 miles by 100 miles” was changed to “100 square miles,” which is very different. The article has now been corrected (or rather, unmiscorrected) and the appropriate intern flogged; our apologies to Ted and Alex.]

This post was coauthored with Alex Carlin, organizer of Let’s Go Solar and instigator of the recent Environment America study (PDF), “On the Rise: Solar Thermal Power and the Fight Against Global Warming.”

Every day more people are finally hearing about what Joe Romm calls “the solar power you don’t hear about” — solar thermal power, utility-scale arrays of mirrors that create heat (and then electricity) so efficiently that they can do everything a coal plant can do except melt the South Pole.

Without any special promotion, solar thermal (concentrating solar power, or CSP) will eventually grow into a major supplier of our electric grid, simply because, according to the California Energy Commission, it is an increasingly economical technology with per kilowatt-hour costs estimated to be 27 percent lower than new integrated gasification combined cycle (IGCC) coal plants with carbon capture-and-storage — 12.7 cents/kWh for CSP versus 17.3 cents/kwh for IGCC plus CCS.

The technology is moving forward, with five plants already operational, eight under construction, and 20 more announced. Several of these plants include on-site thermal storage, an option that makes CSP a reliable source of baseload power.

The problem is the timeline of global warming. If we take seriously what the science is telling us, we must conclude that CSP has arrived in the nick of time. James Hansen’s latest team effort (PDF) tells us that earth has had many eras with ice-free North and South Poles. The report concludes: “If humanity wishes to preserve a planet similar to that on which civilization developed … CO2 will need to be reduced from its current 385 ppm to at most 350 ppm.” On the other hand, if we continue to burn coal for our electric power, those poles will melt, sending sea levels so high that cities like New York and Miami would have no chance to survive.

You probably already knew that, but did you know this? Just 100 miles by 100 miles of CSP installations would supply 100 percent of the U.S. electric grid. That’s being conservative: Ausra’s chairman David Mills pegs the figure at 92 miles by 92 miles. Put similar installations in Morocco for Europe and the Gobi desert for China and we have our golden opportunity — our last chance — of keeping those poles under ice and our cities above water.

How much land is 100 miles by 100 miles?

But we need to get this done fast. James Hansen says that coal emissions must be phased out (PDF) by 2025 (developed countries) or 2030 (developing countries) (PDF). That’s a lot faster than utilities will move on their own. Something has to break through the inertia that seems certain to doom all our best efforts. That something is public clamor. The slogan “100 miles of mirrors” is catchy. It’s simple enough, and it could cause a chain reaction. Bumper stickers, graffiti, calls to talk radio, letters to newspapers, gossiping, rumor milling — it can become a national phenomenon that unites right-wingers with left-wingers to “just build those 100 miles of mirrors.” Why not? It saves our country from near certain doom.

Wind, geothermal, efficiency, and all the other good ideas will have their place. In fact, these additional alternatives mean that we may need far less than 100 miles of mirrors. But because it can provide a direct baseload substitute for coal plants, CSP has a unique role to play in rallying the public around a simple message — and generating public clamor requires an extremely simple message:

You wanna burn coal?
You melt the South Pole!
100 miles of mirrors or it won’t be pretty.
Solar saves Miami and New York City!