One of the livelier debates around climate change involves the question of technology. Do we already have the tools necessary — efficiency, solar power, nuclear, carbon capture and so on — to reduce greenhouse-gas emissions sharply enough to avoid a big rise in global temperatures? Or will we need some new, as-yet-uninvented gizmo to get the job done?

(David Paul Morris/Bloomberg)

So what did the final report find? California could get awfully close — but not quite there — with existing technology. In the journal Nature, Jane Long recently summarized the CCST report’s conclusions: “If California could quickly replace cars, appliances, boilers, buildings and power plants with today’s state-of-the-art technology, replace and expand current electricity generation with non-emitting sources and produce as much biofuel as possible by 2050, the state could reduce emissions by a lot — by perhaps 60 percent below 1990 levels.” Going even further than that, she writes, will take big new technological breakthroughs. And Long’s essay is now provoking fierce debate among energy experts.

First, let’s put those numbers in context. If California did manage to slash emissions 60 percent below 1990 levels by 2050, that would be a mind-boggling shift. And, as former Union of Concerned Scientists clean-energy director Alan Nogee points out, California’s per-capita emissions are already much lower than many other parts of the United States, due to scant coal use and strict building codes. There are fewer “easy” cuts left to make. If California can cut emissions 60 percent with existing technology, other states could presumably do more.

But why the need for new technology? As the CCST found, the most feasible way for California to cut emissions would involve doubling its electricity use. Buildings would get heated with electricity rather than natural gas. By 2050, some 60 percent of cars would have to be plug-ins rather than combustion-powered. And all that extra electricity would need to come from clean sources. That’s a dilemma. If the state relies too heavily on wind and solar, it’ll be difficult to balance fluctuating supplies when the wind’s not blowing or sun’s not shining. The state might have to burn natural gas to balance the load, causing it to miss its targets.

Something else will be needed. Maybe Californians will rekindle their love affair with nuclear power — the CCST found that 30 new reactors could provide two-thirds of the state’s power in 2050, though that means figuring out how to deal with the waste and alleviate public fears. Or perhaps engineers will find a way to capture carbon-dioxide from coal and gas plants and stash it underground. But that’s still a ways off. The same goes for storage technologies and smart grids to smooth out wind and solar supplies. Solar already has a lot of potential as is — happily, electricity use tends to peak when the sun is shining — but higher levels of solar (say) will require new ways to store that energy for darker hours.

One other point: the CCST report explicitly ignores costs. They’re looking at what’s technically doable, not what’s cost-effective. Even though many efficiency measures can save consumers money, a low-carbon push could be pricey. New technology can help here, too. Perhaps that breakthrough will come from a researcher grinding away at a lab, as the experts in this Dot Earth forum suggest. Or, as Joe Romm argues, clean energy could become cheaper as existing technologies get widely deployed, and firms learn how to knock down costs (notice that solar prices have plummeted in the past few years as production has ramped up). Either way, California’s about to put these theories to the test.