No need to feel guilty about the size of your carbon footprint. Book a trip with United Airlines and you can visit its carbon offset program website and pay to offset the greenhouse gas emissions associated with your trip.
You have a choice of three carbon- reduction projects: forest conservation near San Francisco, wind power in Texas and biodiversity preservation in Belize. Basically, US$5 (HK$39) equals a half tonne of carbon.
Website: co2offsets.sustainabletravel international.org/ua/offsets