By Lawrence Summers

With the accumulation of scientific evidence and its persuasive presentation to the public, the global warming debate has reached a new stage. Those who still deny that human activity is warming the planet, or claim that “business as usual” can continue indefinitely without profoundly adverse consequences, are increasingly seen as the moral and intellectual equivalent of those who deny that tobacco has adverse consequences for human health. While there is probably excessive euphoria in some quarters over the economic benefit of green policies, it is now beyond debate that there are huge opportunities to reduce emissions with economic benefit or negligible economic cost. It has been estimated that worldwide subsidies to energy use approach $250bn.