Tempted to obsess over how another personal habit helps or hurts the Earth? Keep surfing with cable or DSL and you might save carbons in the process, according to the American Consumer Institute.

The world would be spared 1 billion tons of greenhouse gases within a decade if broadband Internet access were pervasive, the group's report concluded in October.

Broadband is available to 95 percent of U.S. households but active in only half of them, the study said, noting that near-universal adoption of high-speed Internet would cut the equivalent of 11 percent of oil imports to the United States each year.

How would faster downloads and Web page loads curb the annual flow of globe-warming gases, and by how much? According to the report:

* Telecommuting, a "zero emission" practice, eliminates office space and car commutes: 588 million tons.
* E-commerce cuts the need for warehouses and long-distance shipping: 206 million tons.
* Widespread teleconferencing could bring one-tenth of all flights to a halt: 200 million tons.
* Downloading music, movies, newspapers, and books saves packaging, paper, and shipping: 67 million tons.

The report does not touch on the impact of electronics waste on the planet's health. It is the fastest-growing type of garbage. What of the carbons spent to manufacture the gadgets that get people online? And does heating and cooling an office of many people really expend more pollution than if the staff telecommuted and powered their home offices instead? These and other possibilities remain largely unexplored.