Today, President Barack Obama opened the United Nations climate change summit in New York City with a speech characteristically long on rhetoric and short on specifics. Since the past few months have brought a flood of new facts to the policy debate, let's help Obama by digging into some of the particulars of carbon cutting math.
The aim of this week's meeting is to get 190 nations on the same page for an international deal to replace the Kyoto Protocol. The goal: a new global treaty aimed at getting developed countries to cut their greenhouse gas emissions by 20 percent below the level they emitted in 1990.
Last week, however, climate experts upped the ante, claiming the necessity of much, much deeper cuts. The World Wildlife Federation and the International Institute of Environment and Development issued a joint statement from 40 leading climate scientists declaring that in order to prevent global average temperatures from rising more than two degrees Celsius "developed countries must reduce greenhouse gas emissions by at least 40 per cent below 1990 levels by 2020." In July, the Group of Eight wealthiest nations agreed to limit global warming to two degrees Celsius above pre-industrial temperatures.
Leaving aside the possible impact of such dramatic cuts on the economy: Is it even possible for Americans to cut emissions enough to reach the 40 percent goal in the next decade?
Since carbon dioxide constitutes the bulk of greenhouse gases emitted by the U.S., let's use that as a proxy for figuring out what a cut of 40 percent below 1990 emissions levels would mean. In 2007, the U.S. carbon dioxide emissions totaled around 6 billion metric tons, up from 5 billion tons in 1990, an increase of about 20 percent. So cutting carbon dioxide emitted by 40 percent below the 1990 level would mean that Americans would emit only 3 billion tons by 2020—reducing current emissions by half. The last time the annual U.S. emission of carbon dioxide totaled 3 billion tons was nearly 50 years ago [PDF].
To get a sense of the magnitude of the task, consider that in 1960, the country's population was 190 million, the number of motor vehicles came to 75 million, and real GDP was $2.5 trillion. Americans drove 718 billion miles annually, burning 58 billion gallons of fuel in vehicles that averaged 12 miles per gallon. Today, the 305 million people who live in the U.S. drive 255 million vehicles, and real GDP is $13 trillion. Contemporary Americans drive 3 trillion miles per year, burning 180 billion gallons of fuel in vehicles that average 17 miles per gallon. The good news is that we have become a lot more efficient at producing value per unit of carbon dioxide emitted. In 1960, people produced $800 in GDP for every ton of carbon dioxide emitted. Now, the ratio is about $2,200 of GDP for every ton emitted.
So how might the U.S. cut its carbon dioxide emissions to 1960 levels in 10 years? Let's begin by recognizing that although energy efficiency is not free, I will assume that efficiency improvements will reduce emissions cost-free by 17 percent (the target in the American Clean Energy and Security Act, passed by the House in June) which equals a reduction in carbon dioxide emissions by a little over a billion tons. I will also (generously) assume that Americans will use no more energy in 2020 than they do today; that means that some 2 billion tons of carbon dioxide needs to be cut from current emissions levels in order to get emissions down to 3 billion tons by 2020.
Now let's do some rough number crunching. Burning coal accounts for 36 percent of U.S. carbon emissions, natural gas 20 percent, and oil (gasoline, diesel, jet fuel, and heating oil) 44 percent. Since 90 percent of the coal burned in the U.S. is used to produce electricity, replacing all coal-fired generating plants with zero-carbon electricity generation plants would just about cut emissions by 2 billion tons.
How might this be done? The country could go all nuclear. Currently, 1,400 coal-fired electricity generation plants supply about 45 percent of the country's electricity while 104 nuclear power plants produce roughly 20 percent. So to replace all coal plants with nuclear plants would mean building 250 new 1,000 megawatt nuclear plants over the next 10 years, or about 25 new plants per year. That could be done for about $1 trillion.
But a lot of the people participating in the climate change festivities in New York this week find nuclear power distasteful; they prefer wind or solar power. In that case, all coal fired plants could be replaced with 500,000 windmills at a cost of $1.4 trillion. Similarly, using current conventional silicon solar panels to replace all coal generation would cost $4.5 trillion. (Note: I am using Electric Power Research Institute figures and standardizing wind generation capital costs to a 1,000-megawatt nuclear power plant operating 90 percent of the time, to try to account for the fact that the wind doesn't always blow and the sun doesn't always shine.)
What about natural gas? Since 31 percent of natural gas is consumed to produce 21 percent of U.S. electricity, that means that burning natural gas to generate electricity contributes just about 7 percent to U.S. carbon dioxide emissions, or about 360 million tons annually. Natural gas emits about half the carbon dioxide of coal. The upshot is that replacing all coal-fired plants with 250 1,000 megawatt natural gas plants would reduce emissions by only 1 billion tons, but at a relatively low cost of about $250 billion.
Since two-thirds of all oil in the U.S. is used for transport fuels, this suggests that entirely replacing the current fleet of 255 million vehicles with no-emissions electric or no net-emissions biofuel vehicles would cut 2 billion tons of emissions by 2020. At the current vehicle fleet turnover rate, around 125 million of today's vehicles will be scrapped by 2020. The 2007 Energy Independence and Security Act requires the production of 36 billion gallons of biofuels by 2022 which would be the equivalent of supplying 20 percent of current transport fuel consumption. Earlier this year the Sandia National Laboratory released a highly speculative report that claimed that the U.S. could produce 90 billion gallons of bioethanol by 2030, which would replace 60 billion gallons of gasoline.
Oilman T. Boone Pickens is pushing his plan to use natural gas to power millions of motor vehicles. So let's assume that all 125 million new vehicles will run on compressed natural gas by 2020. Such vehicles emit 25 percent less carbon dioxide and typically cost $6,000 more than conventional vehicles. This kind of vast conversion would reduce carbon dioxide emissions annually by 350 million tons at an additional cost of $750 billion.
So is a 40 percent cut in emissions possible? The foregoing number crunching exercise suggests that it could be. But the commitment is huge: We're talking about the equivalent of shuttering every single one of America's coal plants in favor of hundreds of new nuclear facilities, hundreds of thousands of windmills, or millions of solar panels—or perhaps replacing the entire U.S. auto fleet with zero-emissions vehicles. The magnitude of such an effort would be similar to the projected costs of President Obama's proposed government-funded health insurance plan or the price tag for the War on Terror. These are big changes, not to be glossed over in glowing speeches about international cooperation and our bright green energy future.
Ronald Bailey is Reason magazine's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is now available from Prometheus Books. This column first appeared at Reason.com.