The distributions of the average CO2-equivalent emissions/person/meeting, here split for conferences and schools (since they pursue different goals for participation), show how widespread travel-related emissions are, depending on the meeting.

Not a big surprise, but the higher the amount of local (< 100 km from venue) participation, the smaller the average emissions. However, even meetings with few local attendees can have travel emissions below the average.

I didn't realize that there are far more conferences in Europe than in North America.