Leonardo DiCaprio has lost his cool with a cheeky journalist who implied that his jet-set celebrity lifestyle is at odds with his environmental campaigning.

The actor was in Cannes to attend a screening his latest film, �The 11th Hour,� a documentary about the environment, when he was asked by a reporter whether he had taken a fuel-guzzling flight to the French Riviera.

 "No, I took a train across the Atlantic," was Leo's sarcastic response, before adding, "We're all trying the best we can, truly, we really are."

Leo is just one of the celebrities involved in the �Global Cool� project, an environmental campaign aimed at lowering carbon emissions.