One way is reducing the amount of carbon dioxide he puts into the atmosphere.
He has reduced plane and car travel, for example. In dealing with the latter, first, he owns a variety of cars including a 38 year old Aston Martin, Jaguars, an Audi, and several Range Rovers. Instead of using petro (as the people of the UK say, which is gasoline to us Yanks) he uses "wine" (ethanol) to power the Aston Martin and biodiesel made from used cooking oil on the other vehicles.