He claimed that the Climate Change Act 2008 was "the most expensive piece of legislation ever put through Parliament", and likely to cost hundreds of billions over the next 40 years. In May 2009, Booker spoke at an International Conference on Climate Change organised by The Heartland Institute. In the autumn of 2009, he published "The Real Global Warming Disaster". The book, which became his best-selling work, claims that there is not actually a consensus on climate change, and postulates that the measures taken by governments to combat climate change "will turn out to be one of the most expensive, destructive, and foolish mistakes the human race has ever made". The book was characterised by Philip Ball in "The Observer" as being as "the definitive climate sceptics' manual", in which "he has rounded up just about every criticism ever made of the majority scientific view that global warming, most probably caused by human activity, is under way, and presented them unchallenged".