Halldor Thorgeirsson told journalists gathered at London's Imperial College that world's leaders weren't working hard enough to prevent potentially catastrophic climate change. "We are failing as an international community," he said. "We are not on track."

Thorgeirsson, a senior director with the United Nations Framework Convention on Climate Change, was speaking with two years left to go before the world powers gather in Paris for another round of negotiations over the future of the world's climate, which scientists warn will warm dramatically unless action is taken to cut down on greenhouse gas emissions.

He seemed to strike a pessimistic note, talking down the idea that Paris or any other conference would produce a grand bargain that would ensure the reductions needed to prevent a dangerous warming of the Earth's atmosphere. He even seemed to suggest that a global solution to the issue wasn't likely until the effects of climate change came barreling down on peoples' heads or flooding into their homes.

"I don't think that an international treaty will ever be the primary driver for the difficult decisions to be made," he warned. "It's the problem itself that will be the primary driver and the consequences of that problem."

Quizzed on the repeated failure of the international community to organise a global deal on greenhouse gases, he said that the politicians involved had to be held to account. "This is a question that needs to be asked at the ballot box," he said. "This is a question that needs to be asked of leaders at all levels.