If you have taken steps to reduce your carbon footprint, but you still want to do more, one option is to buy carbon offsets. Offsets are often sold by the ton, and they essentially allow you to pay others to reduce to reduce their greenhouse gases. The money may go to fund capture of methane from a landfill that would otherwise have escaped into the atmosphere, or to protect a tropical forest that would otherwise have been destroyed, releasing greenhouse gases. Offsets can be purchased to balance out the emissions from a plane flight, for Offsets are not a perfect option, since it can be difficult to determine what would have happened in the absence of the offset funds.
Several types of high quality offsets exist, though, and some offset providers make buying an offset easy to do. We are not in a position to endorse any particular offset provider, but you may want to look into them as one of the actions you take to reduce your carbon footprint.