Earth Day Climate Rally features music, speeches and an assist from Mother Nature

It punched holes through the overcast early in the day -- a welcome change for an annual concert that's been particularly soggy in recent years. Last year's event was gray and drippy, and 2008's concert was thunderstormed out before the Roots, who were headlining, could even walk onstage.

Mother Nature must have gotten the memo that this year's awareness-raising, free-admission concert, organized by the Earth Day Network, marked the 40th anniversary of the environmentalist event. Tens of thousands gathered on the grounds between the Capitol and the Washington Monument to hear activists, celebrities and Congress-folk speak about the importance of renewable energy, green jobs and shrinking carbon footprints.

Oh, and there was some music, too. The Roots, the great hip-hop group that recently, finally earned household-name status as the house band on "Late Night With Jimmy Fallon," made a triumphant return to the Mall, scheduled to back performances from Sting, John Legend and a slew of others.

They took the stage late in the afternoon, propelled by Ahmir "?uestlove" Thompson's firecracker drumming and Tariq "Black Thought" Trotter's dexterous rhymes. But their set ended rather unceremoniously when the sound system blew out.

Once organizers resuscitated the P.A., the Roots returned with Staples, the great soul-gospel singer, in tow. After that came Fall Out Boy singer Patrick Stump, who crooned Bobby Womack's "If You Think You're Lonely Now." As surprising as this transformation from emo-dude to blue-eyed soulman: Stump has slimmed down into quite the trim Fall Out Man.

Up next, micro-performances from the inimitable Booker T, the intolerable Joss Stone and Bob Weir of the Grateful Dead -- the Roots playing it cool throughout.

Fans threw their hands toward the sunny skies. Not a raindrop in sight.

The only moisture launched from on high came from the rally's most fiery speakers. More than a few barbs where chucked at Sen. Lindsey Graham (R-S.C.), who on Saturday withdrew his support for a comprehensive climate and energy bill.

As frustrations curdled, issues blurred. "It is time to say no," Rep. Chris Van Hollen (D-Md.) declared from the stage. "No to those that deny the science, no to the flat-Earthers, no to the birthers!"

Backstage, Earth Day Network President Kathleen Rogers was more lucid but equally frustrated. "We have a stunning amount of scientific information that points to tragedy," Rogers said. "We're losing ground every single day in this country and I think the American public deserves to know that we're taking a back seat in the global economy by reducing efforts to go green."

Also backstage, a calm James Cameron was swarmed by reverent photographers as if the director's work on the blockbuster film "Avatar" had transformed him into some kind of eco-deity. His voice barely carried over the hyperventilating camera shutters: SnapSnapSnap "Hopefully, this is a consciousness-raising event . . . " SnapSnapSnapSnap.