Carbon offsets should be used to compensate for that last little bit of carbon emissions you cannot eliminate any other way. They are a supplement to the effort, not a substitute. If you are investing, put your money in projects that will create clean energy—wind farms, solar plants and biomass facility that capture methane and so on.
You’ll do well to have your money supporting energy-efficient and eco-friendly construction. If you have investible surplus, please help launch clean energy education programs.