A single long-haul flight between London and Los Angeles will rack up 2.6 tons of carbon emissions in your personal pollution account.
Most airlines don't yet have options for you to offset these emissions right on the website, but British Airlines and SAS are pioneers here. For other modes of transport, there's not a super-simple way to offset carbon emissions, but these organisations give you a way to offset.
These organisation provide accurate calculators, and full transparency in their carbon offsetting programs. You can use them to offset your emissions with a clear conscience.
Renewable energy in the developing world, including solar power in India and South Africa, and methane entrapment in Thailand.