Today Greenpeace activists evaded security at Heathrow and unveiled a flag on a the tail fin of an airliner to protest plans to build another runway at Heathrow. As noted by Roger Pielke, Jr. these activists really need some perspective. China is building 97 new airports over the next 12 years. Adding another runway to Heathrow will increase air traffic and carbon dioxide emissions, but not nearly as much as 97 brand new airports.