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TWO years ago, was just a Red Bull-slamming high school from Independence, Oregon, who wanted to do something about global warming. Aiming to shake us out of our intellectual torpor, Craven made a YouTube flick called 鈥淭he Most Terrifying Video You鈥檒l Ever See鈥�. It was watched by millions, including you perhaps.

Craven鈥檚 ingenious argument was that when it comes to global warming, the facts we fight over don鈥檛 actually matter. Far more important is that the experiment is already running. We will see soon enough who is right, but in the meantime, Craven believes we should analyse the situation using the tools of risk management. Here, the answer is indisputable. If we take strong action and global warming turns out to be no big deal, we have needlessly incurred a serious economic cost. If we fail to take strong action and global warming turns out to be catastrophic, we have sacrificed the entire planet and everybody鈥檚 future. Clearly, inaction carries the greater risk.

Such is the core argument that took Craven鈥檚 video viral on the web in 2007. Now, 52 later, he has used it as the basis for a book, which is essentially a toolkit for thinking about global warming 鈥� or rather, for avoiding thinking wrongly about global warming 鈥� enlivened by the same everyman charm and humour that made Craven such a popular guide. (Who else would open a section about confirmation bias with an anecdote that begins: 鈥淎 couple of years ago, as part of a spectacular air-guitar leap off a desk during a triumphant routine for my high school鈥檚 lip-synch contest鈥︹��)

Freed from the 10-minute limitation of a YouTube video, Craven now goes far beyond risk management. He also explains how to evaluate the credibility of sources, how to avoid the all-too-human trap of confirmation bias in determining which arguments to trust, and how to think about the nature of science 鈥� always tentative, never certain.

Craven鈥檚 schtick is 鈥渄on鈥檛 just trust me, think for yourself鈥�. Or as he puts it: 鈥淚鈥檓 really just a Joe Schmo science teacher.鈥� His book provides pages where the reader is supposed to jot down his or her own thinking, and has two separate 鈥渃onclusion鈥� chapters, one for the author鈥檚 conclusions, one for the reader鈥檚. The truth, though, is that Craven really is an expert, just of a new breed that didn鈥檛 exist before the internet. In the climate debate, I would rather trust Craven than industrial lobbyists or environmental groups, and I doubt I am alone.

鈥淭his author really is an expert 鈥� one of a new breed that didn鈥檛 exist before the internet鈥�

If his book has a weakness, it is his ultimately unconvincing suggestion that we can avoid debating the science altogether. As Craven himself realised after his first video, which he now advises people not to watch, we cannot manage every conceivable risk. First, we need to know the probability the risk might actually be realised, which brings us inevitably back into a scientific debate. That is precisely the point of Craven鈥檚 鈥渕utant space hamsters鈥� scenario: we don鈥檛 defend the Earth against their genocidal invasion because, well, it鈥檚 a ridiculous threat.

This small flaw doesn鈥檛 make Craven鈥檚 book any less valuable. Indeed, I learned something from it 鈥� an achievement I might have thought impossible given my lengthy immersion in the climate debate. At the beginning of the first chapter, Craven asks readers to write down what it would take to convince them they are wrong about climate change. My own answer: I would change my mind if there were a sudden reversal of opinion in the scientific community. If Craven could get everybody who has weighed in on this debate to go through a similar exercise, Al Gore should share his Nobel peace prize.

In the end, that is Craven鈥檚 real lesson. Before we can be confident about anything, we need to understand our own failings. Or in his words: 鈥淏eing humble about my understanding makes it less likely for the laws of physics to end up spanking me hard.鈥� For anyone planning to enter the global warming shouting match, Craven鈥檚 book is an essential spanking-avoidance device.