Are environmentalists who want fossil-fuel divestment hypocrites if they don’t adopt a radically reduced carbon lifestyle? That’s a common charge among conservatives.

The United States has a long way to go before we get to U.K. levels of emissions. Some of this represents the fact that we have a lot of heavy manufacturing and we produce a fair amount of energy, both of which are very carbon-intensive.

But some of it is also our lifestyles, especially air travel, car travel, living in larger homes that we air-condition and heat to a year-round 70 degrees, and using a lot more energy-intensive devices, from computers and big televisions to refrigerators and clothes dryers.

If environmentalists want everyone in the country to stop doing those things, say conservatives, then they should start doing so themselves — and agitating for things such as institutional air-travel bans that rarely rank high on the priorities of student activists.

Is this fair? OK, a bit, especially because a lot of people I interact with on this issue don’t necessarily seem to have the firmest grip on what’s involved in really cutting back on U.S. carbon emissions. But ultimately, I think it is unfair, for a couple of reasons.

The first thing that environmentalists can argue is that they don’t want to use a carbon tax to make everyone live in caves; they want to use a carbon tax to push toward infrastructure changes and cleaner forms of power that will allow everyone to enjoy a plush lifestyle while emitting less carbon.

In many cases, I think this argument works. Denser urban design would allow more people who want to do so trade in their bigger detached houses for convenience and walkability.

Less carbon-intensive technologies, from renewables to LED lights, could allow people to luxuriate in power without causing the planet to warm. Hybrid cars, driverless cars, smart grids — name your technology; it’s reasonable to say, “We will, but we’re waiting for the market to provide it.”

Is a carbon tax necessary to get us those technologies? Will they arrive even if we have one? You can certainly argue those points. But it’s not obvious to me that the environmentalists have the worst of that argument.

In other areas, however, it’s not fair. At least as it has been explained to me by physicists, air travel inherently requires hydrocarbons; nothing else packs enough energy density into so little weight. Cement making is another ubiquitous industry that is just inherently carbon-intensive, because heating limestone, a necessary step in the process, releases carbon dioxide.

American levels of climate control are going to be very challenging to reach from renewable energy, even if you offset winter’s solar losses with greater use of wind power — at least without going on a nuclear-building binge, which is something that environmental activists don’t seem wildly eager to embrace.

But that still doesn’t make them hypocrites, because they can argue that their behavior won’t make a difference.

If every American turns down the thermostat to 13 degrees Celsius and stops flying and does all the other things that would lower our emissions, we might have a meaningful chance at stopping global warming.

But if a handful of environmentalist activists do this, all that happens is … they’re cold, and no one wants to go on vacation with them. So they make comparatively modest changes, such as take mass transit, rather than give up the laptop and move into a yurt.

I think this is perfectly fair, especially because this is basically my stance. I support a revenue-neutral carbon tax and more funding for renewables research. But in the meantime, I am not going to don sackcloth and (carbon-free) ashes to no possible benefit.

However, I will give conservative critics this: Adopting this stance only makes sense if you don’t believe there’s much power in “setting a good example.” As it happens, consistent with my stance, I do not believe that there is much power in setting a good example, at least not on things that are as central to modern life as breaking apart hydrocarbon chains and using the energy to replace human muscle. I believe that movie stars can inspire idealistic teenagers to go vegan; I do not think that more ordinary-looking adults can convince the majority of Americans to suffer through discomfort and inconvenience for the sake of a hard-to-see threat.

If this is what you believe, then it’s reasonable to go about your life until the day we are ready for collective action. But I must note that this belief is at odds with the faith professed by most environmentalists in the powers of example-setting on carbon emissions.

When it is pointed out (correctly) that China and India’s billions of people currently pose a much greater threat to the atmosphere than rich Americans, environmentalists usually respond by first pointing to the public-relations noise that China is making, even as it continues to construct dirty coal plants as fast as it can pour the concrete, and second by arguing that we need to adopt these changes first, which will set a good example and give us the credibility to ask that China and India follow suit.

I find this belief sincere, touching and almost willfully naive. Radical cuts in our carbon emissions will not cause China and India to follow our example for the same reasons that radical cuts in the carbon emissions of Swarthmore College sophomores will not persuade their fellow students to join them in the yurt. If you can see the one clearly, it should be just as easy to see the other.

So no, I don’t think that environmentalists are necessarily hypocrites when they advocate more radical action than they are willing to take on their own. But I think they should be as clear-eyed about the limits of foreign policy as they are about the limits of their own personal influence.

Megan McArdle (mmcardle3@bloomberg.net), a Bloomberg View columnist who writes on business and public policy, is the author of “The Up Side of Down.”

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