What Obama's pledge to reduce emissions by 83% would mean in practice.
By RICHARD K. LESTER
When President Obama goes to the Copenhagen climate change summit next week, he is expected to once again declare that the U.S. will reduce its carbon emissions 83% by 2050. Even though no legally binding agreement is expected, what Mr. Obama says in Denmark will define the U.S. position in subsequent international negotiations. He will not say how the cuts will be accomplished. For Americans, the details are worth knowing.Annual U.S. carbon-dioxide emissions currently average about 5.5 tons of carbon per person. Achieving Mr. Obama's goal would mean reducing this to 0.63 tons per person by midcentury, taking expected population growth of just under 1% per year into account. If the rest of the world were to do likewise, global carbon dioxide emissions would be 25% lower than today.
Many climate scientists think this would put the world on track to avoid the worst consequences of climate change. Of course, other countries may well have a different view of global equity. This includes China, which in the president's version would have to reduce its rapidly increasing per capita emissions to half the current level by 2050.
Most anthropogenic CO2 emissions come from fossil fuels, so there are two main routes to achieving the president's goal. First, the U.S. must reduce the share of fossil fuels—currently 85%—in the energy supply system, which includes everything from electricity generation and transportation to industrial uses. And second, Americans must use energy more efficiently.
The more we do of one, the less we'll need of the other. But ultimately what's required will depend on America's future economic growth.
Uncompromising environmental advocates argue that the dangers of climate change are so great that carbon emissions must be eliminated regardless of economic impact. Politicians, who must answer to voters, are unlikely to agree. A look at the underlying numbers helps explain.
Assume for now an annual economic growth target of 2% per capita for the next four decades. This would be higher than the disappointing 1.4% of the past decade, but roughly what the U.S. economy has achieved overall since 1970. With this target, the implications of the president's emission reduction goal become clearer.
First start with the key measure of energy efficiency: energy use per unit of economic output. Recently this has been falling by about 2% each year. Suppose that, through more aggressive policies like rewriting building codes to ensure greater energy efficiency, it was accelerated to 3%. In effect, this would mean bringing the rate of progress in every state in the country up to the level of the best state performer. It is not at all clear how this would be possible, but even if it is, meeting the 83% goal would still require extraordinary decarbonization measures on the supply side.
Here is a recipe that would work: Add 30,000 megawatts of new wind turbines every year between now and 2050 (this is nearly four times what was added in 2008, a record year). Add another 35,000 megawatts of solar photovoltaic capacity annually (more than 100 times what was added last year—a record year for solar, too).
That's just the beginning. Now multiply the nuclear reactor fleet fivefold by midcentury. Retrofit all existing coal-fired power plants with carbon capture and storage technology. And build twice as many new plants, also with carbon capture. Natural gas could substitute for coal, but only with carbon capture too. By 2050, the electric power system would be four times bigger than today. Two-thirds of the car and truck fleet would be powered by electricity, and the rest would run on advanced biofuels.
All of this would indeed reduce carbon emissions by 83%. It would also practically eliminate America's dependence on oil imports. But could it be done?
Perhaps, though not without enormous effort. Operating a power grid reliably and economically with intermittent solar and wind resources generating 40% of the electricity cannot be done today. Carbon capture and storage has yet to be demonstrated on a large scale. Meanwhile, a still vocal group of environmentalists remains adamantly opposed to nuclear energy—even though it is the only low-carbon energy source that is both scaleable and already generating large amounts of electricity.
Yet falling short on any of these decarbonization measures would require even more of the others, or even greater energy efficiency gains. Failing that, the only way to reach the 83% reduction goal would be through slower or even negative economic growth, i.e., lower living standards. This is a matter of arithmetic; it cannot be wished away.
The president's expected announcement at Copenhagen is probably the minimum needed to keep international climate negotiations alive. But the implications for U.S. energy are radical in scale and scope. The American public, sensing that the new climate policy will bring higher energy costs and a massive new government presence in energy production, remains unconvinced, to judge by recent poll numbers.
A steady stream of cost-reducing innovations in many different fields of energy technology—if sustained over decades—could bring the nation's climate and energy security goals within reach. But there are profound doubts about the government's ability to engineer this. When Mr. Obama returns from Europe, he will face an even tougher audience at home. Unless he can begin to dispel its doubts, his declaration of intent in Copenhagen will ring increasingly hollow.
Mr. Lester is professor and head of the department of nuclear science and engineering at MIT, where he is also director of the Industrial Performance Center.
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