The top ten ways to cool the planet while you're traveling

... and having fun (by planting trees)

After every 20,000 miles of riding a motorcycle, plant five trees (one tree every 4,000 miles, assuming 40 miles per gallon).

After every 100 hours of riding a jet ski, plant 2 trees (one tree every 50 hours of using a jet ski, assuming gasoline consumption of 2 gallons per hour).

After a weekend of fishing in a pleasure boat, plant one tree (one tree every 10 hours of running a typical fishing boat, assuming 10 gallons per running hour, 5 hours per day, two days per weekend, 26-foot boat, 250-gallon onboard tank).

After a seven-day cruise, plant 1.5 trees (one tree every 4.5 days at sea, assuming consumption of 120 gallons per passenger, generating roughly 1.56 tons of carbon dioxide per passenger). Based on data supplied by Princess Cruises, 585 tons of fuel for a 7-day cruise carrying 1500 passengers. Assumptions: residual fuel, weighing 6.5 pounds per gallon, emits 26 pounds of CO2 per gallon.)

After every 20,000 miles of flying, plant five trees (one tree every 4,000 miles). Based on data supplied by Lufthansa: 121,000 pounds of fuel for a journey of 7,500 km. According to Daniel Lashof, Natural Resources Defense Council, fuel burned by airplanes puts nitrogen oxide and water vapor at 30,000 feet. These two additional greenhouse gases together give as much as twice the global warming effect as the carbon dioxide released by the airplane. For true global cooling flight, three trees every 4,000 miles need to be planted: one tree offsets the carbon dioxide emitted by the airplane over 4,000 miles, and two more trees offset the greenhouse effect caused by the nitrogen oxide and water vapor.

The typical car goes 10,000 miles at 20 mpg, using 500 gallons per year. Plant one tree every 100 gallons or 370 liters (a gallon of gasoline turns into 20 pounds of CO2).

Plant 3 trees to offset the 613 pounds of paper one person uses in a typical year. Remember those maps, brochures and flyers that you collected while on vacation? Plant some trees and stop feeling guilty about all the trees that died to distribute that information!

After every 20,000 photocopies, plant a tree (one tree every 22,000 sheets of paper or 44 reams). You can travel guilt-free, knowing that the postcards, photos and the newsletter that you'll send out at the end of your trip will be "global cooling."

After every 10,000 kilowatt-hours, plant 10 trees (one tree every 1000 kilowatt-hours). We use electricity everywhere, so use it without guilt by planting trees!

A one-time purchase of 200 trees will absorb 5 tons of carbon dioxide each year for the next 40 years, the amount of CO2 emitted by the typical car getting 25 miles per gallon. For a car getting 15 mpg, you should plant 320 trees.