F. K. Weyerhaeuser Fellow Steven F. Hayward

The usual chorus of environmentalists and editorial writers has chimed in to attack President Bush's recent speech on climate change. In his address of April 23, he put forth a goal of stopping the growth of U.S. greenhouse gas emissions by the year 2025.

"Way too little and way too late," runs the refrain, followed by the claim that nothing less than an 80% reduction in emissions by the year 2050 will suffice--what I call the "80 by 50" target. Both Hillary Clinton and Barack Obama have endorsed it. John McCain is not far behind, calling for a 65% reduction.

We all ought to reflect on what an 80% reduction of greenhouse gas emissions by the year 2050 really means. When we do, it becomes clear that the president's target has one overwhelming virtue: Assuming emissions curbs are even necessary, his goal is at least realistic.

The same cannot be said for the carbon emissions targets espoused by the three presidential candidates and environmentalists. Indeed, these targets would send us back to emissions levels last witnessed when the cotton gin was in daily use.

Begin with the current inventory of carbon dioxide emissions--CO2 being the principal greenhouse gas generated almost entirely by energy use. According to the Department of Energy's most recent data on greenhouse gas emissions, in 2006 the U.S. emitted 5.8 billion metric tons of carbon dioxide, or just under 20 tons per capita. An 80% reduction in these emissions from 1990 levels means that the U.S. cannot emit more than about one billion metric tons of CO2 in 2050.

Were man-made carbon dioxide emissions in this country ever that low? The answer is probably yes--from historical energy data it is possible to estimate that the U.S. last emitted one billion metric tons around 1910. But in 1910, the U.S. had 92 million people, and per capita income, in current dollars, was about $6,000.

By the year 2050, the Census Bureau projects that our population will be around 420 million. This means per capita emissions will have to fall to about 2.5 tons in order to meet the goal of 80% reduction.

It is likely that U.S. per capita emissions were never that low--even back in colonial days when the only fuel we burned was wood. The only nations in the world today that emit at this low level are all poor developing nations, such as Belize, Mauritius, Jordan, Haiti and Somalia.

If that comparison seems unfair, consider that even the least-CO2 emitting industrialized nations do not come close to the 2050 target. France and Switzerland, compact nations that generate almost all of their electricity from nonfossil fuel sources (nuclear for France, hydro for Switzerland) emit about 6.5 metric tons of CO2 per capita.

The daunting task of reaching one billion metric tons of CO2 emissions by 2050 comes into even greater relief when we look at the American economy, sector-by-sector. The Energy Department breaks down emissions into residential, commercial (office buildings, etc.), industrial, and transportation (planes, trains and automobiles); electricity consumption is apportioned to each.

Consider the residential sector. At the present time, American households emit 1.2 billion tons of CO2--20% higher than the entire nation's emissions must be in 2050. If households are to emit no more than their present share of CO2, emissions will have to be reduced to 204 million tons by 2050. But in 2050, there will be another 40 million residential households in the U.S.

Today, the average residence in the U.S. uses about 10,500 kilowatt hours of electricity and emits 11.4 tons of CO2 per year (much more if you are Al Gore or John Edwards and live in a mansion). To stay within the magic number, average household emissions will have to fall to no more than 1.5 tons per year. In our current electricity infrastructure, this would mean using no more than about 2,500 KwH per year. This is not enough juice to run the average hot water heater.

You can forget refrigerators, microwaves, clothes dryers and flat screen TVs. Even a house tricked out with all the latest high-efficiency EnergyStar appliances and compact fluorescent lights won't come close. The same daunting energy math applies to the industrial, commercial and transportation sectors as well. The clear implication is that we shall have to replace virtually the entire fossil fuel electricity infrastructure over the next four decades with CO2-free sources--a multitrillion dollar proposition, if it can be done at all.

Natural gas--the preferred coal substitute of the moment--won't come close. If we replaced every single existing coal plant with a natural gas plant, CO2 emissions from electric power generation alone would still be more than twice the 2050 target. Most environmentalists remain opposed to nuclear power, of course. It is unlikely that renewables--wind, solar, and biomass--can ever make up more than about 20% of our electricity supply.

Suppose, however, that a breakthrough in carbon sequestration, a revival of nuclear power, and a significant improvement in the cost and effectiveness of renewables were to enable us to reduce the carbon footprint of electricity production. That would still leave transportation.

Right now our cars and trucks consume about 180 billion gallons of motor fuel. To meet the 2050 target, we shall have to limit consumption of gasoline to about 31 billion gallons, unless a genuine carbon-neutral liquid fuel can be produced. (Ethanol isn't it.) To show how unrealistic this is, if the entire nation drove nothing but Toyota Priuses in 2050, we'd still overshoot the transportation emissions target by 40%.

The enthusiasm for an 80% reduction target is often justified on grounds that national policy should set an ambitious goal. However, claims on behalf of alternative energy sources--biofuels, hydrogen, windpower and so forth--either do not match up to the scale of the energy required, or are not cost-competitive in current form.

How on God's green earth will we make up the difference? Someone should put this question to the candidates. And not let them slide past it with glittering generalities.

Steven F. Hayward is the F. K. Weyerhaeuser Fellow at AEI.