In this post I will lay out “the solution” to global warming, focusing primarily on the 14 “stabilization wedges.”

Part 1 argued that stabilizing atmospheric concentrations of carbon dioxide at 450 ppm is not politically possible today, but that it is certainly achievable from an economic and technological perspective. It would require some 14 of Princeton’s “stabilization wedges” — strategies and/or technologies that over a period of a few decades each reduce global carbon emissions by one billion metric tons per year from projected levels (see technical paper here [PDF], less technical one here [PDF]). The reason that we need twice as many wedges as Princeton’s Pacala and Socolow have said we need was explained in Part 1.

I agree with the IPCC, which concluded last year that “The range of stabilization levels assessed can be achieved by deployment of a portfolio of technologies that are currently available and those that are expected to be commercialised in coming decades.” The technologies they say can beat 450 ppm are here. Technology Review, one of the nation’s leading technology magazines, also argued in a cover story two years ago, “It’s Not Too Late,” that “Catastrophic climate change is not inevitable. We possess the technologies that could forestall global warming.”

I do believe only “one” solution exists in this sense — We must deploy every conceivable energy-efficient and low carbon technology that we have today as fast as we can. Princeton’s Pacala and Socolow proposed that this could be done over 50 years, but that is almost certainly too slow.

We’re at 30 billion tons of carbon dioxide emissions a year — rising 3.3 percent per year — and we have to average below 18 billion tons a year for the entire century if we’re going to stabilize at 450 ppm. We need to peak around 2015 to 2020 at the latest, then drop at least 60 percent by 2050 to 15 billion tons (4 billion tons of carbon), and then go to near zero net carbon emissions by 2100.

That’s why a sober guy like IPCC head Rajendra Pachauri, said in November: “If there’s no action before 2012, that’s too late. What we do in the next two to three years will determine our future. This is the defining moment.” Or as I told Technology Review, “The point is, whatever technology we’ve got now — that’s what we are stuck with to avoid catastrophic warming.”

If we could do the 14 wedges in four decades, we should be able to keep CO2 concentrations to under 450 ppm. If we could do them faster, concentrations could stay even lower. We’d probably need to do this by 2030 to have a shot at getting back to 350 this century. (And yes, like Princeton, I agree we need to do some R&D now to ensure a steady flow of technologies to make the even deeper emissions reductions needed in the second half of the century.)

I am not going to focus on the politics, policies, market factors, or mindset needed to achieve these 14 wedges. That will be the subject of Part 4. But, needless to say, none of this can happen without a serious price for carbon dioxide and a very aggressive technology deployment effort.

So here is the basic solution. I have thrown in a couple extra wedges since I have no doubt that everybody will find something objectionable in at least two of these wedges. This is what the entire planet must achieve:

  • One wedge of vehicle efficiency — all cars getting 60 mpg, with no increase in miles traveled per vehicle.
  • One of wind for power — one million large (2 MW peak) wind turbines.
  • One of wind for vehicles — another 2000 GW wind. Most cars must be plug-in hybrids or pure electric vehicles.
  • Three of concentrated solar thermal — about 5000 GW peak.
  • Three of efficiency — one each for buildings, industry, and cogeneration/heat-recovery for a total of 15 to 20 million gwh.
  • One of coal with carbon capture and storage — 800 GW of coal with CCS.
  • One of nuclear power — 700 GW plus 10 Yucca mountains for storage.
  • One of solar photovoltaics — 2000 GW peak (or less PV and some geothermal, tidal, and ocean thermal).
  • One of cellulosic biofuels — using one-sixth of the world’s cropland (or less land if yields significantly increase or algae-to-biofuels proves commercial at large scale).
  • Two of forestry — End all tropical deforestation. Plant new trees over an area the size of the continental U.S.
  • One of soils — Apply no-till farming to all existing croplands.

That should do the trick. And yes, the scale is staggering.

Why not more than one wedge of CCS? That one wedge represents a flow of CO2 into the ground equal to the current flow of oil out of the ground. It would require, by itself, recreating the equivalent of the planet’s entire oil delivery infrastructure. I also think that CCS has practical issues that will limit its scale, not the least of which is that I doubt it will be among the cheaper solutions. But that is another blog post.

Why not more than one wedge of nuclear? Based on a post last year on the Keystone report, to do this by 2050 would require adding, globally, an average of 17 plants each year, while building an average of 9 plants a year to replace those that will be retired, for a total of one nuclear plant every two weeks for four decades — plus 10 Yucca Mountains to store the waste. I also doubt it will be among the cheaper options. And the uranium supply and non-proliferation issues for even that scale of deployment are quite serious.

Note to all: Do I want to build all those nuclear plants? No. Do I think we could do it without all those nuclear plants? Probably. Therefore, should I be quoted as saying we “must” build all those nuclear plants, as the Drudge Report has, or even that I propose building all those plants? No. Do I think we will have to swallow a bunch of nuclear plants as part of the grand bargain to make this all possible and that other countries will build most of these? I have no doubt. So it stays in “the solution” for now. (Note to self: Are you beginning to sound like Donald Rumsfeld? Yes.)

This is not to say the two wind power wedges (4000 GW peak total) would be easy — we only built 20 GW last year. We would need to average 100 GW/year through 2050. But I do think it is ecologically and economically possible, as I think all the other wedges are, too.

But none of the wedges is easy. That’s why getting to 450 ppm is not yet politically possible. Not even close. As noted, part 4 will discuss the politics, policies, market factors, or mindset needed to achieve these 14 wedges.

Three more points: First, it bears repeating that the wedges are not analytically rigorous (as I explained in Part 1), but they are conceptually useful. We might need a few more or a few less.

Second, based on comments posted on this blog, it seemed to make more sense to present the total solution first before posting on each individual wedge in detail. But I do expect to blog in detail on each of these wedge in the coming months.

Third, if you don’t like one of those wedges, you need to find a replacement strategy. Other possibilities can be found here [PDF], but I think the ones above are the most plausible by far, which tells you how dubious some of Princeton’s other wedges are (I’m talking about you, would-be hydrogen wedges). Could a bunch of breakthrough technologies substitute for some of the above wedges? That is far more implausible, as I will discuss in Part 3.

This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.