A massive polar ice cap seems to be melting. What are we going to do to stop it?

The answer, as I've often posited in this space, is "likely nothing." Oh, I don't mean literally "nothing"; I'm sure people will continue to write angry editorials and buy "green" consumer products. But I don't think we're likely to do much in the way of actually reducing greenhouse-gas emissions, which contribute to the climate change that is melting the ice caps.

A few weeks back, this drew a censorious e-mail from a longtime commenter who noted that he was making a serious commitment to emissions reduction by, among other things, buying a Chevrolet Volt.

My response to him is that "buying a Volt" does not constitute getting serious about carbon emissions. The idea that we can save the planet while barely changing our consumption patterns is one of the reasons that we are not going to actually "get serious" about global warming.

Start with a fact: The world emits 32.5 billion metric tons of carbon dioxide every year. About two-thirds of that comes from the top 10 carbon-emitting nations:

What do you notice about this list? First, it's heavy on producers of fossil fuels -- Russia, the U.S., Canada, Saudi Arabia. Second, it's heavy on population; together, these countries account for about half the world's people. And third, it's heavy on rich countries; how much carbon you consume correlates with how much stuff you produce.

Now look at another fact: how that ranking changes if you look at per-capita emissions, rather than total emissions:

The first thing is obvious: The list is now dominated by producers of fossil fuels, rather than population. But the second is that the countries at the bottom are big, poor countries that are still trying to get rich.

Let's say China doesn't aspire to U.S. levels of consumption and industrial output, just to dainty Japanese levels. That still means raising its per-capita carbon emissions by nearly 50 percent -- or 3.6 billion metric tons of carbon a year. To offset those emissions, the U.S. would have to cut its emissions by just about two-thirds. And that's just to keep the world's emissions static -- the level at which the polar ice cap is already melting, remember? If we want emissions to fall, we'll have to do even better.

Of course, Europe could help. But Europe is going to be needed to offset India's and Brazil's emissions increases, which -- if those countries manage to get rich -- will be even more dramatic than China's. At some level, it becomes mathematically impossible for the rest of the world to become as wealthy as us while reducing emissions to a safe level.

Are there efficiency gains to be had? Of course there are. In fact, per-capita emissions have been going down in all those wealthy countries, including the U.S. But the reductions have been dwarfed by gains in the developing world, especially China.

The calculation above already assumes that as China gets richer, it will experience massive efficiency gains. Currently, China has about one-seventh the per-capita income of Japan but two-thirds the carbon emissions -- in part because China relies on cheap coal for electricity and heating, in part because the world has outsourced her dirty, inefficient production to Chinese industry. I'm assuming that China will eventually reach, and be satisfied with, Japanese levels of consumption and energy efficiency. If not, world emissions will soar still higher.

What would it take for us to cut our carbon output by a third? Well, look at where our consumption goes:

Commercial and residential emissions are mostly heating and cooling; industry is nonelectric greenhouse-gas emissions (for example, making steel uses carbon from fossil fuels not only to melt the metal ore, but also as part of the chemical process that makes it strong; cement also emits carbon as part of the production process).

We can break it down still further, into the sectors that use this energy. Here's what electricity consumption looks like:

And here's transportation broken down:

Passenger cars do consume a lot of energy. But they are 45 percent of 28 percent of our emissions, or about 13 percent of the total. By one estimate, driving a Volt in a middle American city such as Houston saves about 25 to 30 percent of the carbon emissions associated with driving. That suggests that if everyone in the country bought a Volt, we might shave our emissions by 3.5 percent -- impressive, and maybe worth doing, but hardly enough to offset the rise in China's emissions.

But it's not practical to imagine that everyone in America is going to buy a Volt. Many people need to haul large numbers of children or lots of stuff. Or they regularly drive much farther than the Volt's electric range, which reduces the savings. And I haven't even touched on the economic expense -- that big, bulky battery adds a lot of cost to the car.

All of which is a long-winded way of saying that this isn't some easy fix that consists of buying somewhat more expensive products while keeping our way of life essentially the same. America's outsized carbon emissions are not mainly due to the fact that we drive huge sport utility vehicles. Our outsized carbon emissions are mainly due to the fact that we produce a lot of fossil fuels and a lot of stuff. We like to live in large houses that have several hundred square feet of space per person. We like to be warm in winter and cool in summer, in a climate that has a lot more temperature extremes than Europe. We grow and eat a lot of food. When stuff breaks, we throw it out instead of relying on Mom's skills with a needle and Dad's carpentry mojo for repairs.

There are, to be sure, people in America who actually are getting serious about reducing their carbon footprint: They shun large houses, air travel, air conditioning, out-of-season produce, most manufactured goods. But this is a tiny minority, and very few of the people I hear saying we should "get serious" about global warming have any intention of living this way, though they might be happy to buy a Volt. And if a government tried to enact the kind of carbon tax that would force them to live this way, they'd fire their legislators as soon as they figured out that it was costing them $1,000 or so a year just to run the clothes dryer.

Moreover, many of the reductions you could theoretically imagine -- lowering our emissions by ceasing to extract oil and natural gas from the earth, shifting further away from manufacturing -- seem broadly incompatible with the other policy goals these same people have, such as providing remunerative and stable employment for millions of lower-skilled American workers.

Since we are probably not going to conserve our way to safety, and hopefully not going to invade China to keep it from getting rich, if we want to keep the climate from warming further, then we have something much more important to do than buy Volts: find a stable, cheap renewable resource that can actually replace all our power generation needs, or figure out an engineering solution that can take greenhouse gasses out of the atmosphere, or keep the planet from warming anyway. Perhaps those things are not possible. But however difficult they are, they seem more likely than getting Americans to drop their per-capita emissions back to something more like Slovakia's.

To contact the author on this story:
Megan McArdle at mmcardle3@bloomberg.net

To contact the editor on this story:
Brooke Sample at bsample1@bloomberg.net