Of the millions of Greenies who claim to be deadly serious about Saving the World from global warming by limiting carbon emissions, how many are really sincere?

There's one surefire test of sincerity: Do they demand reductions in immigration to the U.S.?

Answer: almost none of them do.

A Google search for “carbon emissions“ brings up 3,680,000 web pages. (August 8, 2010). Add “immigration reduction“ to the search, however, and the hit count falls to 114.

The causes of global warning are disputed, but let's assume for the sake of analysis that human output of “greenhouse gases” does indeed cause global warming. It ought to be close to self-evident that immigration to America increases this country's—and the world's—output of those gases.

The logic is very simple: If immigrants from poor countries successfully assimilate to American norms of earning and consuming, they, and their descendents, will emit vastly more carbon than if they stayed home.

According to the UN's International Energy Agency, residents of America in 2007 put out an average of 19.1 tons of carbon dioxide, the chief greenhouse gas, by fossil fuel combustion—e.g., by driving around, by being warm in winter and cool in summer, and by watching TV.

In contrast, the residents of Mexico each emit 4.1 tons per year. In other words, the typical inhabitant of America churns out 4.6 times as much carbon dioxide as the typical inhabitant of Mexico.

So, if an average Mexican immigrates to the U.S. and fully assimilates to average American patterns of earning and spending, he will emit 4.6 times as much carbon dioxide as if he stayed home in his own country. (Even more important are the impact of his descendents, which we'll get to below).

This table gives a sampling of the carbon emissions per capita of immigrant importing and exporting countries.

For example, Australians, in the grand tradition of Mad Max, pump out an American-like 18.7 tons of carbon dioxide per year. Therefore, if an average Australian moves to the U.S. and adopts the average American's way of life, the net effect on global carbon emissions would be negligible: i.e., the “Immigration Multiplier” is barely above 1.0.

The right hand column in the table lists the number of adults who want to immigrate to each country according to a vast Gallup poll of 259,542 people in 135 countries. Around the world, no less than 700 million adults—one out of six of the total—want to emigrate. America is the first choice of 165,000,000. Plus 60,000,000 others prefer to move to Australia or Canada, which are both America Jr. from the perspective of per capita carbon emissions.

In contrast to the Immigration Destination Countries, which typically emit much carbon per person, the Immigration Source Countries don't. Thus the Immigration Multiplier for Mexico is 4.6 because residents of Mexico pump out only 22 percent as much carbon per person as residents of America. The -15,000,000 in Mexico's right hand column means that in the Gallup survey, 20 percent of the adults still left in Mexico said they would like to leave. That equates to 15,000,000 adults (n.b. this is not counting children and future offspring).

Of course, it's also important to remember that not all immigrants come from Mexico. Many Americans don't realize it, but by Third World standards, Mexicans on average aren't particularly poor. According to the CIA World Factbook, there are no less that 5,366,204,659 people living in countries with lower average per capita incomes than Mexico.

To put it another way, 79% of world lives in countries poorer than Mexico.

(Of course, the Mexican average is a little skewed by the World Richest Man, Carlos Slim, major creditor of the New York Times, and his fellow oligarchs.)

It's commonly implied in the MSM that Mexicans immigrate to the U.S. to avoid seeing their children die of starvation. Yet, life expectancy in Mexico (76.3 years) is now essentially as high (97.5 percent) in the U.S.

No, Mexicans don't immigrate to America to live longer—they immigrate to live larger: to have a large vehicle, a large house, a large TV, and a large family. All of which equate to large carbon emissions.

American white liberals tend to imagine that Mexico has a donkey-based economy, and thus that Mexicans must be blank slates who would naturally follow white liberals' advice.

Bunk. Stemming from the discovery of oil in Mexico (by the great American geologist Everette Le DeGolyer in 1910), Mexico has long been, by Third World norms, car-crazy and energy-profligate. The government of Mexico has subsidized gasoline purchases for decades.

When my Southern California family drove to Mexico in the 1960s, we'd debate whether to fill up in San Diego or wait until Tijuana for the cheap (but noxious) Pemex gas.

To return to my theme: In most other immigrant-exporting countries, the carbon emission immigration multiplier is substantially higher than that of Mexico. For instance, if a normal Dominican immigrates to America and successfully assimilates his carbon emissions would increase 9.7 times. For most Central Americans, the Immigration Multiplier is around 20X. For Haitians, it's 79.3X.

But because Mexicans comprise the single largest group of immigrants, and because their carbon Immigration Multiplier appears to be fairly typical, I'll use Mexicans to illustrate the effects of immigration.

When I've brought these inconvenient truths up in discussions, on the rare occasions when Save the Worlders respond logically, they sometimes dredge up the response that Mexico will, surely Real Soon Now, emit as much carbon per capita as the U.S.

I don't see much evidence for that in the UN figures. Mexico's per capita carbon emissions were estimated to be 18 percent as high as America's in 1982, and 22 percent as high a quarter of a century later in 2007. At that rate, it would take many generations to close the gap.

Global warming activists haven't found many other objections to sputter. Their thought processes tend to be restricted to Immigration Good! Carbon Bad! Does not compute… These are HateStats!

This is representative of the kind of childishness that passes for political discourse in America today. The feuds of junior high school girls are more reality-based than what passes for current elite discourse, which consists largely of 99 percent fact-free status posturing.

Why this intellectual decline? At present, Americans are, by historical standards, extraordinarily rich. Thus, we assume we will always be able to afford to indulge in petulance rather than use facts and logic.

Of course, we aren't quite as rich as we thought we were three years ago. But our intellectual maturity hasn't caught up yet.

So let's examine some logical objections to my argument for the global warming worriers.

Consider a very simplified model in which an immigrant from Mexico will either succeed or fail at assimilating to American norms on two dimensions: Earning and Consuming.

Let's start with the upper left hand corner of this quadrant: American Dream. In this scenario, the typical Mexican who immigrates to the U.S. achieves the American Dream. He succeeds at consuming like an American (e.g., big SUV, big air-conditioned house in suburbs, big TV, and so forth) and also (this is important) earning like an American. Therefore, his contribution to global greenhouse gas emission will be vastly greater than if he stayed home in Mexico. Even more importantly, so will his descendants' carbon emissions.

In the lower right corner, we see the opposite outcome: Undercaste. Here, the Mexican immigrant fails to earn a better life for himself and his offspring. He does not succeed at assimilating to American norms of earning and consuming. He and his descendents ride the bus to their low-productivity jobs. Under this scenario, Mexican immigrants don't pay enough taxes to make up for all the social services they consume and all the damage they do to the public schools. Yet, at least from a greenhouse gas perspective, an Undercaste outcome would be great news.

But, we are constantly admonished that that it's racist to even entertain the thought that many Mexicans are unlikely to fully assimilate.

In the lower left corner is the unspoken liberal assumption about the impact of Mexican immigration: Ecotopia. This logical possibility is the favorite of the sort of white liberals who have farm simulators on their iPhones. Of course, it is the least logical or possible.

They assume Mexican immigrants rapidly achieve American levels of income to pay the taxes for all the social programs that progressives favor. Yet, for unexplained reasons, the Mexican immigrants and their progeny choose to live like Portland trustfunders whose hobby is a “sustainable” lifestyle based on walking to Whole Foods for heirloom tomatoes. On the rare occasions when these Mexican immigrant families drive anywhere, it would be in their vegetable oil-powered Toyota Prius hybrid.

The Ecotopia assumption is the only logical way to square enthusiasm about immigration with alarmism about greenhouse gases.

Of course, this view is seldom articulated fully—because it's absurd to anybody who knows any Mexicans other than that cool guy from Cuernavaca they met at film school.

It's not a coincidence that perhaps the finest contribution by Chicanos to American popular art in the mid-20th Century was the customized lowrider car. Mexicans love cars—the bigger the better.

In contrast, how many Mexicans do you see driving Prius hybrids? As far as I can tell, Toyota hasn't yet bothered selling its Prius in Mexico (population 112,000,000). Nor do many Mexican-Americans want one either. A poll of readers of Prius Chat found that only 3 percent were Hispanic. If you are familiar with the ethnic layout of Los Angeles County, you'll enjoy this map of Prius registrations by zip code.

Whatever stereotypes Larry David's environmentalist ex-wife entertains about flyover folks' lack of environmental sensitivity are much truer of Mexican immigrants.

But that never comes up in global warming worriers' conversations—because they never pay attention to Mexicans.

In the upper right corner of the quadrant, the worst of both worlds happen: Bush Bubble. In this scenario, the Mexican immigrant and his offspring spend like an American—buying a big house, a big vehicle, and a big TV, all on credit—but earn like a Mexican. They eventually default on their mortgages.

And, indeed, this is roughly what happened in the exurbs of California during the Bush Bubble years: a baby boom, a housing and spending bubble, and a crash of defaults.

Moreover, the more you think about the impact of Mexican immigration, the worse it is for carbon emissions. Immigration contributes both directly and indirectly to sprawl. Mexican immigration to cities tends to drive Americans, including blacks and American-born Hispanics, to the exurbs to find decent public school districts—at the cost of long commutes for parents. For example, immigration into Los Angeles, with its mild climate, spawned an enormous housing bubble in the hot Inland Empire, where air conditioning costs are high.

As Joel Kotkin has often pointed out, most immigrants in the 21st Century want to spend as little time in the inner city as possible and instead move directly to a suburb or exurb.

Finally, Mexican immigrants tend to have higher birthrates in America than they would have had if they stayed home. In California in 2005, foreign-born Latinas were having babies at a rate of 3.7 children per lifetime versus about 2.4 for women in Mexico and 1.6 for American-born white women in California.

On the whole, we can be sure that immigration's overall effect will be some combination of American Dream, Undercaste, and Bush Bubble. It's not a coincidence that Ecotopias, such as Portland, are found far from the Mexican border.

Let's assume for the sake of calculating immigration's impact on carbon emissions in 2050 that the optimists are right and American Dream is the standard outcome.

When the impact of greenhouse gases on global warming is finally brought to the attention of global warming activists, many scoff at the idea that immigration could have any sizable impact on the U.S. population.

But that is simply ignorance. The Pew Research Center reported in 2008:

“If current trends continue, the population of the United States will rise to 438 million in 2050, from 296 million in 2005, and 82% of the increase will be due to immigrants arriving from 2005 to 2050 and their U.S.-born descendants, according to new projections developed by the Pew Research Center.”[Immigration to Play Lead Role In Future U.S. Growth, by Jeffrey Passel and D'Vera Cohn, February 11, 2008]

So, that's 116 million additional people in America due to immigration from 2005 onward. (Perhaps another 50 or 60 million of that forecasted population of 438 million would be due to immigration from 1965-2004.)

Assuming that these immigrants emit carbon at the American average, the U.S. in 2050 will emit 39 percent more carbon than if an immigration moratorium had been imposed in 2005.

Confronted with this logic, global warming activists tend to say: Well, All We Have To Do is cut emissions per capita even more to make up for immigration.

But immigration means that we're falling behind by about one-third before we even begin to cut. How does that make sense if we have to Save the World?

Each American would have to personally reduce his or her carbon emissions by 28 percent by 2050, simply to make up for post-2005 immigration. And that's just to keep the national carbon emission total flat. Lowering U.S. emissions becomes even more difficult due to immigration.

Conclusion: When you find yourself in a hole, the first thing to do is to stop digging.

America is widely denounced for accounting for about 20 percent of world carbon dioxide outputs. Yet, the 2005-2050 addition to the American population caused by immigration would alone account for an additional eight percentage points of the global total.

The net effect of post-2005 immigration to America (taking into account what the immigrants would have emitted back home in Mexico or other countries), is six or seven points. In other words, by 2050, post-2005 immigration to the U.S. will have the impact on greenhouse gases of another one-third of an America coming into existence.

The impact by 2100 will be significantly greater.

Bottom line: U.S. immigration restriction is a relatively simple and sure way to restrict greenhouse gas emissions.

That it almost never comes up in current debate says a great deal about what might laughingly be described as modern “thought”.

[Steve Sailer (email him) is movie critic for The American Conservative.

His website www.iSteve.blogspot.com features his daily blog. His new book, AMERICA'S HALF-BLOOD PRINCE: BARACK OBAMA'S "STORY OF RACE AND INHERITANCE", is available here.]