Not content with saving the planet on celluloid, the Hollywood star Josh Hartnett is trying to emulate that success in real life.
Josh: climate change campaigner
He's one of the big-name stars who've signed up for a new campaign to combat climate change.
It's called Global Cool - and it aims to inject a little glamour into the slightly prosaic subject of energy saving.
Last night, Josh met the Prime Minister at a special reception at Downing Street.
And this morning, we talked live to the actor, whose screen credits include Black Hawk Down, Pearl Harbor and Lucky Number Slevin.