Spinal Tap is back, and this time the band wants to help save the world from global warming. The fictional heavy metal group immortalized in the 1984 mockumentary, "This Is Spinal Tap," will reunite for a performance at Wembley Stadium in London as part of the Live Earth concerts scheduled worldwide for July 7.

The original members of Spinal Tap will be there: guitarist Nigel Tufnel (played by Christopher Guest), singer David St. Hubbins (Michael McKean) and bassist Derek Smalls (Harry Shearer). Rob Reiner, who both directed "This Is Spinal Tap" and played the fake documentarian Marty DeBergi in the film, will also be in attendance.

A new 15-minute film directed by Reiner on the band's reunion will play tonight (April 25) at the opening night of the Tribeca Film Festival in New York. The festival is to open with a showing of several global warming-themed short films produced by the SOS (Save Our Selves) campaign. SOS is also putting on the Live Earth concerts, to be held across seven continents.

"They're not that environmentally conscious, but they've heard of global warming," Reiner says of Spinal Tap's often clueless members. "Nigel thought it was just because he was wearing too much clothing -- that if he just took his jacket off it would be cooler."

Spinal Tap has reunited several times since the film, but hasn't for a number of years. For the band, whose last album was 1992's "Break like the Wind," the occasion warranted a new single: "Warmer Than Hell."

Reiner provided a sneak peek at the lyrics: "The devil went to Devon, it felt like the fourth degree / He said, 'Is it hot in here, or is it only me?'"

The director said the new short film explains what the band has been doing with their lives lately. Nigel has been raising miniature horses to race, but can't find jockeys small enough to ride them; David is now a hip-hop producer who also runs a colonic clinic; and Derek is in rehab for addiction to the Internet.