Global travel website Expedia.com is now offering travelers the ability to purchase carbon offsets: carbon dioxide reduction measures used to help cancel out the greenhouse gas emissions that lead to global warming.

Expedia is offering the service through TerraPass, the leading retailer of greenhouse gas reduction projects in the U.S.

"Expedia is dedicated to promoting responsible tourism, and we're proud to extend environmentally conscious options to our travelers," said Steven McArthur, President, Expedia North America Leisure Travel Group. "We are committed to making a positive impact on travel and tourism through industry advocacy, destination support and the promotion of responsible tourism. Offering TerraPass carbon offsets is just one way we invite our customers to join us in this endeavor."

Airline travel currently accounts for about 13% of American transportation-based emissions of carbon dioxide, the primary greenhouse gas responsible for global warming. To help address this, Expedia is partnering with TerraPass to make it simple for environmentally conscious travelers to be carbon-balanced travelers by purchasing a TerraPass from Expedia as part of their trip.

Expedia travelers can now pay a small fee to sponsor a measured, verified reduction in greenhouse gas emissions directly proportional to the emissions created by their plane flight. TerraPass funds domestic clean energy projects, such as wind farms, innovative "cow power" methane capture plants on American dairies, and the retirement of carbon offsets on the Chicago Climate Exchange.