Carbon offsets for driving and flying not so hot

If you plant some trees, is it OK to drive a sports utility vehicle that is not fuel efficient? The question is not as silly as it sounds. People worried about global warming increasingly are trying to "offset" the carbon dioxide -- the leading greenhouse gas -- they spew into the atmosphere when they drive, fly or flick on a light. One idea popular with the eco-conscious is to have trees planted for them. You get to keep driving and flying, but those trees are supposed to suck in your trail of carbon.

Whole forests have been funded by tree-loving celebrities like Leonardo DiCaprio and the band Coldplay, and more modest packages tailored to typical consumers are proliferating. But some researchers say planting trees -- while a good thing -- is at best a marginal solution to global warming. Still others decry tree planters who continue to jet off to Cannes, drive their SUVs or generally fail to reduce their fuel-hungry lifestyle.

To those critics, plantings and other carbon offsets are like the medieval practice of selling indulgences to wash away sins: It may feel good, but it doesn't solve much. "The sale of offset indulgences is a dead-end detour off the path of action required in the face of climate change," says a report by the Transnational Institute's Carbon Trade Watch. ... The science is sound: Trees take in carbon dioxide as part of photosynthesis and store the carbon.

But even conservationists caution it's not as simple as planting a sapling so you can crank up the air conditioning without guilt. Offset groups use averages to estimate how much carbon a given tree or forested acre can capture. For instance, the nonprofit Conservation Fund figures that each tree planted captures less than 1½ tons over 100 years.

To put that in perspective, consider that about 7.3 billion metric tons of carbon dioxide was produced from the burning of fossil fuels worldwide in 2003, the most recent estimate available. And how much carbon dioxide a tree can soak up varies, said John Kadyszewski of Winrock International, a nonprofit that works on environmental projects. A huge California redwood might have 30 tons of carbon stored while a 100-year-old pine might have less than a ton.

"Trees are all different," said Kadyszewski, coordinator for ecosystem services for Winrock, "and the amount of carbon in the tree depends on how old it is and where it's growing and what kind of tree it is." ...

There are other potential problems, however. Some researchers suggest forests in the snowy North might actually increase local warming by absorbing sunlight that would otherwise be reflected into space. And dead, decaying trees release some of that captured carbon back into the atmosphere. Maybe most importantly, some researchers say it's simply not possible to plant enough trees to have a significant effect on global warming.

Plant a tree, drive a big SUV?

You can download the report, The Carbon Neutral Myth - Offset Indulgences for your Climate Sins

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