Thom Yorke has asked US fans to sign the Stop Climate Change petition
Bloc Party, Glasvegas and Jarvis Cocker also play the Austrian bash
'You have to be honest if it's not working,' says Brian Message
Colin Greenwood says band are looking forward to 'dark' headlining set
Guitarist says the group is trying to help musicians and fans
Thom Yorke alludes to teen star's temper tantrum
They get together under the 'Featured Artist Coalition' banner
See the band preparing to play '15 Step'
'I'm gonna ruin them!' declares the teen star
Director 'McG' says Yorke might contribute