I was struck with another case of SIWOTI syndrome in a link I followed from Michael Tobis' Only In It For The Gold blog. He linked to a post called "Walking Back to Happiness" at the blog site Hot Topic from New Zealand. There, one Tom Bennion, who hosts a site called stopflying.org/, gave a very thorough exposition of the rationale behind his decision to stop travelling by air and his rebuttals of the counterarguments he's encountered when explaining his position to others.
In his brief autobiographical introduction he explained that he's a married, 46 year old lawyer (don't get me started, perhaps the legal profession is different in New Zealand) with three small children. He spends some bytes implying but not stating that many climate scientists who undoubtedly should know better exhibit hypocrisy by flying, especially for vacations.
Well, be that as it may, I commented that no single act (at least not one ordinarily carried out by a "typical" westerner) is as damaging to the environment in terms of carbon footprint and other environmental degradation as bringing a child into the world. So "pot-kettle-black" and all that. I was accused of being "another Malthusian." I did mention resources but my comment was meant to home in primarily to carbon footprint. Now I concede that having a child is more meaningful than flying to Copenhagen, even if it's for a conference on climate change. But it's still a decision to take an action much more likely to damage the Earth for future generations.
Or so I think. But I haven't run the numbers to get an estimate, so I'd best do so. Should it turn out that I'm incorrect, I'll apologize on the site. As usual, this will involve much estimating. I'll use estimates that make the best case that the child is likely to be less harmful, so I'll use a relatively high number of flights over very long distances and use New Zealand rather than U.S. primary energy consumption.
I'll start with a comparison of the lifetime primary energy use of a New Zealand resident which should be a reasonable proxy for the carbon emissions consequent to supplying that energy. Starting with the Energy Information Agency website I find that New Zealand converted primary energy at a per capita rate of 211.2*10^6 btu/year in 2006 (a rate of a bit over 7000 watts as compared to about 11,000 in the U.S.). And at this post at the Litebucket site it's stated that New Zealand derived 71% of it's primary energy from fossil fuels in 2008. As an aside, the other 29% was derived from renewables, a very laudable figure. So, the average New Zealander converts about 0.71*211.2*10^6 or 150.0*10^6 btu/year of fossil fuel energy (regular readers know I hate saying "consumes energy"). Now, I'll assume that a child lives to be 70, so he or she will consume 70*150*10^6 btu or 10.5*10^9 btu in his or her lifetime.
Now let's look at flying. I'll assume that a heavy user flies a round trip of 3000 miles (6000 miles out and back) twice per month, so this heavy airline commuter logs 144,000 miles per year. Let's suppose he or she does this over a 40 year period and hence totals 5.76*10^6 miles. This sad person will be assumed to be on a plane that's 80% full. This site shows that the worst airline gets a trifle over 60 seat miles per gallon of jet fuel, I'll use that. The assumption of 80% full reduces this to 48 miles per gallon for the individual, and 1/48=.0208 gallons/mile. Multiplying this by 5.76*10^6 miles, we find that this heavy airline user will be responsible for the burning of 120,000 gallons of jet A fuel. Here we find that Jet A releases 123,608 btu/gallon so our traveler will convert (123,608 btu/gallon)*(120,000 gallons)=14.83*10^9 btu during his or her flying career. This is about 1.4 times the energy converted by the average New Zealander during his or her lifetime.
Now, it may be objected that there are many variables not considered (type of flying, increasing efficiency of the New Zealander lifestyle, and many, many more) but the two scenarios, child and extreme air traveler are of the same order of magnitude. The writer of the post in question has three children. If we consider that it's not unreasonable for a person to replace him or herself and his or her spouse, the writer has added one beyond that. So the one child beyond the replacement number is on the order of 2/3 as intensive an emitter of CO2 as what is by any reasonable judgement an extreme user of airline travel. Look for my tepid mea culpa at the site.