Last time I booked plane tickets there was an option to pay to offset the CO2 emitted by the flight. Looking at their programs, one was to plant trees, the other one was to plant less trees but give people in Africa and India more efficient wood burning stoves. Are any of these making a dent in the carbon emissions or is it just feel-good?

I would be willing to pay double the plane ticket price if it meant actually making a difference (sleeping better at night would also be a bonus).