Despite the near-perfection of HotOS’09, which I’ve commented on already multiple times (1, 2), one thing that did bother me about the location was the distance. Given that I led a discussion about sustainability during the think big session, I felt obligated to put my money where my mouth was, and today for the first time purchased carbon offsets to cover the trip from Boston to Zurich.

According to, $36.51 was enough to offset my air travel, and this included considering the effects of something called “radiative forcing”, which I thought was sort of interesting. Their explanation:

At high altitudes, the effect of greenhouse gases is considerably
different than on the ground level. Aircraft also emit water vapor
during flight which can cause the formation of ice clouds, called
contrails. Where contrails persist, cirrus clouds begin to form which
have an additional impact on global warming. Clouds can have a double
effect on radiation: they warm the earth by reducing the amount of
radiation from the earth that escapes into space but also cool the earth
by reflecting the sun’s rays back into space. However, contrails lead to
a net warming factor, which is estimated to be 2.7 times the normal
effect (IPCC, 1999).

Anyway, did this make me feel better about the trip? I don’t know. Are carbon offsets perfect? Probably not, but long-distance air travel is a luxury few can afford and it seems reasonable to expect that the privileged few can keep track of their impact on the environment. In my HotOS’09 survey I suggested that USENIX begin offering carbon offsets as part of their registration fee. Maybe they could give people who purchase them a green-backed badge, or something? That’d be cool.