Offsetting emissions

I'm flying quite a lot this year, so I used the (not particularly user-friendly) CarbonNetural flight calculator to give me some idea of my total emissions. Most people fly less than this in a year, I'm sure, but then again I can think of very many people who fly a lot more. In any case, here are my flights for the year, which collectively account for more carbon emissions than the rest of my life combined:

Flight	Tonnes of CO2
New York–Acapulco return	0.8
New York–Albuquerque	0.4
El Paso–New York	0.3
New York–St Louis return, six times	2.4
New York–London return	1.2
London–Berlin	0.1
Munich–London	0.1
New York–Los Angeles	0.4
Long Beach–San Francisco	0.1
San Francisco–New York	0.4
New York–Portland (Maine) return	0.2
New York–Washington return	0.2
New York–Tucson return	0.8
New York–Ushuaia return (via Santiago)	2.3
Total	9.7

These numbers are inprecise, of course: there's no generally-accepted way for calculating the carbon emissions one is responsible for when taking an airplane. What kind of airplane do you base the model on? What percentage occupancy do you assume? How much cargo do you model? What do you use for the CO2 equivalent of other greenhouse gases emitted? And, most crucially, what multiplier do you use for the extra harm caused by emissions at 35,000 feet?

In any case, the cost to offset 9.7 tonnes of CO2 emissions, according to the Climate Care calculator, is £72.75, which is $137.75 at today's exchange rate. A significant sum, but certainly an affordable one, so I'm happy to offset my flight-related emissions for the year with one donation.

But the weird thing, to me, is that all of the websites I can find about carbon offsets seem to be based in the UK or Canada. People there – at least the environmentally-responsible ones – are very likely to know about offsetting their emissions. In the US, however, when I bring up the subject, I'm generally greeted with blank stares. Some high-profile Americans offset, of course: this article cites Al Gore and Dave Matthews. But the concept is still not generally known about in this country.

What I would love to see would be the ability for flyers to offset their carbon emissions when they buy their plane tickets, rather than having to proactively go to some other website entirely. It shouldn't be too hard for a progressive airline like Virgin or JetBlue to add a little button on their ticket-sales page, saying "offset your carbon emissions from this flight for an extra $22" or whatever – many more people would do that, I'm sure, than currently go to places like Climate Care. Of course, all donations would be tax-deductible.

At the very least, if the airlines won't do it, might not one of the big travel booking sites give it a go? I'd probably switch from Orbitz to Travelocity, say, if it had those kind of environmental credentials.