Air travel by some estimates already accounts for around 4% of total global emissions and, with the recent explosion of cheap airfares across the globe, it is the fastest growing component of GHG production. Not only that - the emissions produced from burning jet fuel at high altitudes are compounded, often expressed using a radiative forcing index (RFI) as a multiplier for the effect - I've found calculators that use 1.9, 2.7, and 3.0 for this multiplier. The emissions calculator documentation for Atmosfair and ClimateCare seem to do a good job explaining the effects of radiative forcing, which has a severe effect above 9000 meters (roughly 29,500 feet) - less than the cruising altitude for planes going further than about 700 kilometers.
Nonetheless, the GHG-producing effects of my flying exploits over the last few months (I did a full analysis - 64,115 miles - absolutely absurd) make me feel criminally guilty. From the climate change seminar I took in the spring, I learned a bit about the nascent voluntary carbon offset market - allowing people and businesses to give money directly to carbon-reducing projects in order to claim the associated offset. This is a quickly growing market in the US, already surpassing the $100 million USD mark I believe. I made the decision that I would purchase offsets. Though it does feel like I'm purchasing "environmental indulgences," I contend that considering where I am today, this is among the better things I can do now that the damage has already been done. Not only that, if I choose my offset vendor well, this money can go to support projects with goals I believe in.
So given my decision to purchase offsets, there were a couple of important decisions to consider: who to buy offsets from and how many to buy?
I'll start with the latter challenge - how should I evaluate the GHG-producing effects of all of those miles? It does not appear that there is an authoritative carbon calculator for air travel, though the UN International Civil Aviation Organization (ICAO) is trying to create one. However, as you'll see from the results below, there is a wide variation in this measurement from other calculators I used to capture the carbon equivalent effects of the 64,115 air miles I've recently traveled:
| Calculator Used | Carbon equivalent (lbs. CO2) | Comments |
| Terrapass | 19,606 | Run by some Wharton grads and based in SF (yay!), but recently got some bad press for purchasing offsets that didn't pass the additionality test (see below). |
| UN ICAO | 20,417 | Painfully buggy. The mission of this site uses all publicly available data, but for simplicity takes averages of all of the flights that are taken for specific routes (i.e. not just for the type of plane you flew on, but a weighted average all the planes that fly that route) - not that big a deal, but less exact. |
| ClimateCare | 29,400 | Developed its model based on a well-written commissioned study from Oxford University. |
| Atmosfair | 52,781 | A German company that focuses specifically on air travel and quotes (expensive!) offset prices in Euro. Man, it hurts to be on the dollar. Atmosfair goes to great lengths to estimate all of the intracacies of the carbon effects of air travel. Interestingly, the calculator tells me that my recent 16-hour JFK-BOM flight is too long to be a single flight. It sure felt that way. |
| carbonfund | 63,675 | Uses simple multipliers to come up with its numbers, and uses a radiative forcing factor from a potentially-outdated IPCC study (1999). |
It seemed that Atmosfair and ClimateCare had the most complex models of all of these, taking pains to account for such specifics as altitude profile variations, holding patterns, detours, and taxiing. Additionally, it's not clear that the lowest two of these results consider radiative forcing in any way. Since I appreciate the scientific pains behind their efforts, I settled on using Atmosfair's estimate for my offset purchase.
The next challenge was to figure out where to purchase the offsets. To evaluate different offset vendors, I developed a list of what I feel are the most important criteria in selecting an offset vendor:
* Transparency - how well can I evaluate how much of the money I am giving is actually to the project I am funding? Carbon Catalog does a good job explaining and dissecting this criterion, not to mention providing a survey of a number of different offset vendors (85 at the time of writing).
* Profit/Nonprofit - does the company intend to make money from my funding? This issue cuts both ways - for-profit companies have a goal to make more money (a definite ethics concern), but are often run more efficiently than nonprofits for precisely the same reason. I can't make a sound global argument either way - this is most definitely a personal choice.
* Additionality - how can I be assured that the money I am providing is producing an incremental reduction in carbon? This tends to be the most difficult criterion to evaluate, and is often one salient argument point against voluntary carbon offsets. It's subtle - I suggest you look up additionality on the internets if you're not familiar with the concept .
* Country - Call me a jingoist/nationalist pig, but in this case, I think it's really important to support an offset vendor in the USA. Why? Well, we have a big problem in the states. Bigger than any other country in the world. For example, in 2006, California (the state) used more oil than India, China, or any other country (!) in the world. Any global solution to the climate change conundrum has to start in the USA - no question in my mind. By supporting a USA vendor, I can contribute to the overall size of the voluntary carbon offset market, an institution which I feel is important for the perception that the USA is doing something about this problem. Simply put - increased action in one area (e.g. the voluntary carbon offset market) encourages action in other related areas (climate change policy, consumer goods availability, etc.).
Using the guide on the Carbon Catalog website (linked above), I selected Carbon Counter, namely because they had projects that used on-grid power (I'm a huge fan of increasing electrical efficiency) and they had the highest reported percentage of money going directly to projects (92%). Plus, those Oregon folks are granola-awesome. To let you know how this carbon-reducing adventure finished, I ended up offsetting 24 metric tons of CO2 at a cost of $12/ton; thus, for my ridiculous travel (64,115 miles, at a cost of nearly $6,000), carbon offsets only cost $288, or less than 5% of the airfare. Really, people - this is not a debilitating expense.
Now, I don't intend for this to be an authoritative diatribe on this topic, but I thought I'd offer a couple thoughts on my experience purchasing voluntary carbon offsets. Also, obviously, eliminating air travel entirely is the best way to reduce my carbon footprint. I have not yet decided how to address this issue in my life, but I am beginning to recognize that I need to stay out of the air as much as possible...
