This short and readable book is a fresh approach to the very vexed and angry debate about this topic. Mr Craven sets out, not to find an answer to the question in the title, but to help us - the readers - to find our own answers. The thrust of his book is this: what criteria are we using to make up our minds between 'warmers' and 'skeptics'? And how can we use those criteria consistently, so that we think rationally rather than irrationally, and select evidence fairly rather than just to meet our own preconceptions?
What is particularly good about the book is the way the author forces us to confront our own prejudices and the biases inherent in our own thinking ('Assumptions training', pp 49-51 and 59-75). A particularly acute example is 'confirmation bias' - Peter Wason's 1960 experiment that shows our tendency to seek out views that support ours, instead of views that challenge or falsify our view. An even better example is his insistence that we actually write down the factors that make us believe a particular source (e.g. peer-reviewed paper, well respected scientist, someone you might expect NOT to hold that view) - so that when we come across a view, we have to assess it on the merits of its source, not just on whether it confirms our preconceptions.
By way of example, my own criteria for deciding who to believe are
1 - takes a reasoned, not a moral view of the issue: open-minded, not fanatical
2 - uses (and checks) primary sources, speaks with data
3 - argues rationally and follows that argument through
4 - has perspective, sets this issue in the widest possible context
5 - has a long view
6 - puts forward falsifiable views
7 - prepared if necessary to 'swim against the current'
The view taken by Mr Craven - and well argued - is that global warming is a real and present menace and a top priority for action. My current view (which has changed, and may change again) is a different one. However, I would certainly say that on his own criteria, and his own evidence, he justifies his position clearly, well, and without rubbishing his opponents. (A particularly noteworthy example of this is his treatment of Bjorn Lomborg. Lomborg is usually dismissed out of hand by those who disagree with him; Craven assesses him and his credibility rationally and respectfully, as he does with all those he cites.)
My only criticism of his book - and it is one which certainly does not invalidate its basic method - is that his argument is rather closely tied to the United States and therefore misses some of the strongest sceptics. I would see it as a stronger book if he included Nigel Lawson's 'An appeal to reason' (particularly the second edition, 2009), Christopher Booker's 'Scared to death' (2007), Patrick Michael's 'Meltdown' (2004/2007, though this is published by the Cato Press), Dan Gardner's 'Risk: the science and politics of fear' (2008), and Svensmark and Calder's 'The chilling stars: a new theory of climate change' (2008). For this reason I'd give the book a 4 rather than 5. However, I should in all fairness note that although these authors meet all my criteria for influencing my opinion, they don't meet all Mr Craven's!
Overall the book offers a new and original way of looking at this very vexed, angry, debate - one which is too often a shouting match, and indeed a jihad. All power to Mr Craven for enabling us - as Nigel Lawson begs us - to take 'a cool look at global warming'.