These two were among protests arranged in 15 US cities by the Rainforest Action Network in advance of Saturday's national Step It Up 2007 campaign to raise awareness of human-caused climate change.

The brainchild of Bill McKibben, an environmentalist at Middlebury College in Vermont, the campaign is meant to culminate in a day of climate action aimed at cutting carbon emissions by 80 percent by 2050.

Rather than a mass march on Washington -- reminiscent of anti-war protests of the 1960s and 1970s -- the campaign called for local events around the country. So far, these include a hike to the Hollywood sign in Los Angeles, a march and rally in Seattle and a solar-powered concert and fair in Tucson, Arizona.

"When we were trying to pick a date, we didn't want to do it on Earth Day because we didn't want to step on the events that people would already be planning," McKibben said in a telephone news briefing.

"We were sort of thinking ... one day a year for the Earth doesn't seem to be working out to be quite enough -- maybe we need two and maybe we need a kind of an Earth Week, and I think that's what we're trying to lead into here."

SUPREME COURT AND SHERYL CROW

He acknowledged that the movement to curb global warming got a boost from the April 2 Supreme Court decision that found the US Environmental Protection Agency has the power to regulate greenhouse gases as a pollutant, as well as two reports by the Intergovernmental Panel on Climate Change released in April and February of this year.

These reports offered scientists' consensus that humans almost certainly caused recent global warming and that the poorest countries will suffer most from it.

The drumbeat of activity is hardly confined to grassroots protest and official rulings and documents. California Gov. Arnold Schwarzenegger, a Republican, drew headlines during a visit to Washington this week by telling environmentalists they need to make their cause sexy and mainstream.

Pop musician Sheryl Crow and Laurie David, producer of the Academy Award-winning documentary film on global warming, "An Inconvenient Truth," embarked on a tour of US college campuses, riding in a biodiesel-powered bus. The tour's final stop is Washington on Earth Day.

The star of "An Inconvenient Truth," Al Gore, had hoped to have a rock concert in Washington spotlighting the problems of climate change, but was thwarted by schedule conflicts on the National Mall and then by congressional Republicans who opposed such an event on the grounds of the US Capitol.

Instead, the "Live Earth" concert will be held on July 7 at Giants Stadium in New Jersey, just across the Hudson River from Manhattan.