The Hockey Stick and the Climate Wars: Dispatches from the Front Lines

Planets are much, much larger than people. But our numbers are large, our technology extends our reach and we now affect the state of the Earth. Fortunately, perhaps, we are also moderately observant. Technology extends our reach here, too. So as well as changing the composition of the atmosphere appreciably, we can monitor the effects.

Both are things to wonder at. It is astonishing that an IQ-enhanced primate has attained a level of technical and social organisation where the average global temperature, say, is not only a meaningful concept but also one we can measure. We can even unearth traces of its past trajectory. Also astonishing, if less welcome, is the fact that the same species is raising that temperature faster than at any time in the geologic past.

Wonder, though, is not the foremost response to either of these facts. Fear, doubt, denial, obfuscation, lies, low politics and dirty dealing figure more prominently, alongside hope, missionary zeal, relentless moralising and apocalyptic prophecies.

Michael Mann has been in the centre of this emotional maelstrom. The co-author of papers that offer some of the best readings of past global temperatures, he is identified with the so-called "hockey stick" curve of the book's title. The plot, of Northern hemisphere temperatures, shows relatively little variation over the millennia (the shaft), topped by a sharp upward trend in the most recent decades (the blade). As a meticulous piece of science that produces a memorable visual signature, the hockey stick - confirmed since its first appearance in 1999 by several independent studies - has featured prominently in efforts to communicate climate science and what it means for us all. It has also evoked repeated, relentless attacks: on the original papers, on climate scientists in general, and on Mann himself.

Mann's book relates the science and the responses to it in great detail. Much of the story he tells is familiar - the importance of the temperature record from virtually every book or report about climate change and his critics' bogus invocations of "sound science", as detailed in Naomi Oreskes and Erik M. Conway's scholarly study Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming (2010). But his personal testimony is still valuable. The twists and turns of the discussion are not that interesting in themselves - Mann is telling the story, after all, and he generally comes out on top, or at least is encouraged by support from his peers even when there are political setbacks. The book's pay-off, though, lies in the overall impression he builds of the value of one researcher's determined defence of the science as it is - imperfect, beset by genuine disagreements over how best to extract signal from noise, but the best information we have.

It is a necessary defence and the cost is clearly high. Mann is nothing if not dogged, obviously likes a (scientific) argument, and is not easily daunted by legal threats or denunciations in the US Senate. Many others would be, but they may find here some helpful tactics to adopt, and a few to avoid, when battle is joined. The main one, which does incur that high cost, appears to be an indefatigable commitment to challenging critiques of the work, and to document that effort as thoroughly as possible. The fact that Mann still has the energy to do it all again here, in a 200-page text with more than 100 pages of notes, is impressive in itself. He is even cautiously optimistic about the future. Although, as he says, "the scientific community is, at present, ill-equipped to deal with direct assaults on its integrity", it is learning. The work of resisting those assaults is hard but in the end, he suggests, it gets results.