Review: Stabilization Wedges: Solving the climate problem for the next 50 years with current technologies by Robert Socolow and Stephen Pacala

by Michael Kelberer

When it comes to solving the global warming problem, most of the airtime goes to hyping new technologies that will, deus ex machina, magically materialize to solve the problem for us. While we wait for techno-miracles, however, the problem gets worse.

In a paper published in Science Magazine in 2004, and reprised in an updated and more accessible version as part of Scientific American’s September 2006 issue (“Beyond Carbon”), Socolow and Pacala argue convincingly that (a) we cannot afford to wait for a technological breakthrough to solve our global warming problem, and (b) we don't need to. Everything we need to know to get started, we know already.

First, the authors define the problem in way that lets us set a tangible goal. They focus on the biggest cause of global warming – carbon dioxide (CO2) emissions. The consensus opinion is that if we can avoid a doubling of the atmosphere’s CO2 concentration (compared to pre-industrial times), we will probably avoid the worst effects of global warming. The pre-industrial CO2 concentration was about 280 parts-per-million, and we’re already at 375 parts-per-million. To be on the safe side, they target stabilizing the atmospheric concentration of CO2 at 500 parts-per-million.

One way to achieve this target, according to climate models, is to adopt a two-part, 100-year strategy: Phase I is to stabilize our CO2 emissions at the current level for the next 50 years, and in Phase II substantially reduce them (by half or two-thirds) over the following 50 years. It’s Phase I that the authors address in this paper.

What does “stabilize our CO2 emissions” mean in real life?

Right now we are emitting about 7 billion tons of carbon into the atmosphere each year. If the trend of the last 30 years continues (the “business as usual” scenario), that amount will double to 14 billion tons of carbon per year by 2056. So, to limit emissions to the current level, we have to find ways to eliminate carbon dioxide sources that, if left unchecked, would by 2056 be producing that additional 7 billion tons per year.

While there is no single, 7-billion-ton magic wand available with today’s technologies, the authors say, a large selection of technologies that each could achieve a 1 billion ton reduction in 2056 emissions are readily available. We can achieve the goal, but we’ll need to move on several fronts at once.

In coming up with a list of such technologies, the authors took a deliverately conservative approach. A technology could make their list ONLY if:

(1) The technology is a significant departure from business as usual; i.e. the result of a new and deliberate policy intervention. For example, if you believe that the automobile industry will naturally develop cars with double the gas mileage by 2056, then you can’t count those carbon savings since these savings are already in the “business as usual” forecast. If, however, you believe that this mileage-doubling will only happen if the government enacts new regulations to make it happen, then you can count the new regulations.

(2) The technology is already commercially feasible and only needs to be scaled up in application. They don't count the much-hyped hydrogen fuel cell technology because no practical versions have been invented yet.

Even with these restrictions, the authors have created a list of fifteen proven technologies that would each produce at least one billion-ton reduction in 2056 carbon emissions if we only had the political and social will to implement them. They note that since some of the savings overlap, we may have to choose more than seven to achieve the 7 billion ton reduction goal. For example, if we clean up our electricity production facilities, then the savings we can accomplish by using that electricity more efficiently go down.

So what are these strategies? Here are a couple of them:

Don’t build coal-fired power plants. “Ending the era of conventional coal-fired power plants is at the top of the decarbonization agenda,” say the authors. In the "business as usual" scenario, several thousand such plants would be built between now and 2056. We could achieve a 1 billion ton carbon reduction by not building 700 of them, or by replacing 1400 of these with natural gas-fueled plants (which emit half as much carbon). Avoiding the construction of new coal-fired plants is an urgent matter, since these plants, once built, tend to remain in operation (and emitting all that carbon) for 40-50 years.

Put the carbon back where we found it. Where we do build new coal-fired plants, for each 800 of them that install carbon-capture-and-storage (CCS) facilities to trap 90% of their carbon emissions we would achieve another billion-ton reduction in carbon emissions. This CCS technology is being used today by oil companies, who trap CO2 emissions from their refineries and inject the gas into their oil reservoirs to force out remaining oil.

Build green. Two of the major consumers of electricity are residential and commercial buildings. Doubling the energy efficiency of these buildings by installing modern appliances and lighting would create another billion-ton reduction.

Double gas mileage. Our fleet of automobiles makes the second largest contribution to CO2emissions in the United States. If we could double their fuel efficiency, we could save another billion tons of annual carbon emissions by 2056. As theToyota Prius demonstrates, this is feasible today.

And the list goes on.

Even though the authors emphasize immediate applications of existing technologies for the first 50 years of their strategy, they say we must continue to develop new technologies. Stabilizing our carbon emissions is not enough – to avoid doubling the CO2 concentration we still have to reduce carbon emissions substantially in the second 50 years of this strategy, and we do not currently have the technology to accomplish that. New technologies, which often have 30-50 year development cycles, would arrive just in time to help us in Phase II.

Drs. Socolow and Pacala are both part of the Carbon Mitigation Initiative, which in turn is part of the Princeton Environmental Institute. More on their approach, including research details and explanations of their calculations, is available through the CMI website: www.princeton.edu/~cmi