SUNNYVALE, United States — As part of an ambitious new plan to fight global warming, the internet giant will reduce its energy use and invest in emissions-fighting projects to make its operations carbon neutral.

By the end of 2007, Yahoo! intends to be fully carbon neutral. The company says it has already begun reviewing proposals for the first carbon-offset projects it will invest in, and reviews of the final batch of projects will occur over the rest of 2007.

In order to determine how much carbon-dioxide the company would have to offset, Yahoo! first measured its total carbon-dioxide output from October 1, 2005, to September 30, 2006. When the results are validated by a third-party, the company will be able to accurately gauge how well it's achieving its goal.

In a blog post today, Chief Yahoo David Filo wrote, "While doing our homework on this, we measured our carbon footprint and discovered that Yahoo! going carbon neutral is equivalent to shutting off the electricity in all San Francisco homes for a month. Or, pulling nearly 25,000 cars off the road for a year."

Among the steps Yahoo! has already undertaken to reduce its energy use are purchases of green power near its California headquarters; running its Hillsboro, Mass., office on 100 percent renewable energy; using power management controls to turn off non-essential and unused lighting. The company also provides incentives to employees to reduce the pollution caused during their commutes, by offering Wi-Fi-enabled shuttle vans, encouraging employees to bike to work and discounts on public transit tickets.

Yahoo! is also seeking input from its uses through a thread posted by Filo on Yahoo! Answers.