Delta Air Lines, the dominant carrier at Minneapolis-St. Paul International Airport, became the first major airline to offer a carbon-offset program in 2007.

Delta has a Carbon Emissions Calculator on its website (tinyurl.com/y5r29psl), where you can plug in your flight's origin and destination and get your personal "carbon cost." Minneapolis to Los Angeles International Airport, for instance, produces 0.227 metric tons of carbon per passenger, for a personal carbon cost of $3.41. Minneapolis to Tokyo adds nearly 1 metric ton of CO2 to the atmosphere per passenger, for an offset cost of $14.Of course, nothing's stopping you from buying an even larger offset.

Delta's program allows you to donate to the nonprofit Nature Conservancy, with your choice of environmental projects to support. The Rio Bravo Climate Action Project in Belize reduces carbon emissions through the protection of forest lands threatened by conversion to agriculture. The Clinch Valley Conservation Forestry Program protects and manages 22,000 acres of forestland in southwestern Virginia. Delta also touts a project supporting the Valdivian Coastal Reserve in southern Chile. You can also opt to donate your Delta frequent-flier miles to the Nature Conservancy.

Other airlines serving MSP that offer their own carbon-offset programs include United, JetBlue, Alaska Airlines, Air Canada and Icelandair. Icelandair's program, for example, helps you donate to the cultivation of forests in Iceland. According to the airline's own calculator (icelandair.com/about/carbon-calculator), a round trip between Minneapolis and Reykjavik amounts to a $12 donation to plant seven trees in the island country.

Simon Peter Groebner