About 20 years ago, I (Bill) earned a company-sponsored sabbatical, 4 weeks of extra vacation. Jan and I wanted to travel somewhere that was off the usual travel paths and see something different. We settled on Tonga, an archipelago about a third of the distance between New Zealand and Hawaii. Tonga is a kingdom that has never been colonized. Once there, we planned to visit each of the three main island groups in the country.

Traveling to Tonga required 2 flight segments:

1. United Airlines from Portland to Honolulu
2. Air New Zealand from Honolulu to Tongatapu, Tonga (Fuaʻamotu International)

From the main island of Tongatapu, we visited the other two main island groups over the following two weeks. We flew on Twin Otters on the now defunct Royal Tongan Airlines.

1. Tongatapu to Vava’u Island
2. Vava’u Island to Ha’api Island
3. Ha’api Island to Tongatapu

For the two of us, the international flights (all emissions data courtesy of atmosfair with a radiative forcing index of 3) emitted an estimated 4.8 metric tons CO2e, to Honululu and 6.2 metric tons CO2e to Tonga.

The inter-island flights were much less. This is badly estimated at 0.6 metric tons CO2e. I could not find any data on the Twin Otter model and used a roundtrip to Vava’u with a 20% increase to account for the stop in Ha’api.

So together we accounted for 11.6 metric tons of CO2e. That is a substantial fraction of the 2009 US annual per capita CO2 emissions (17.2 or 38.4 for the two of us).

For comparison, estimates for other long-haul flights are Seattle to Heathrow for 2 people emitting 9.7 metric tons and Los Angeles to Singapore for 2 people emitting 25.2 metric tons.