The American leader, who has been condemned throughout his presidency for failing to tackle climate change, ended a private meeting with the words: "Goodbye from the world's biggest polluter."
He then punched the air while grinning widely, as the rest of those present including Gordon Brown and Nicolas Sarkozy looked on in shock.
But didn't have the guts to tell him what a disgusting piece of work he is.
"Before I leave I'll just piss all over you", said he. Well no, he didn't but he might as well have. I imagine if he'd pissed on Gordon Brown that gent would have declared, "Oh, that's lovely and warm Mr. President."