‘The Planet Can’t Keep Doing Us A Favour’ By David Cromwell Sometimes we get so sick of the phrase 'history in the making' that the brain tends to switch off. What is it this time?, we sigh. A new high-tech piece of military technology that will  boost US killing power ? A big jump in a newspaper's  online advertising revenue ? The world's best footballer,  Lionel Messi , joining 'an exclusive list of adidas athletes to have their own signature product'? Sometimes the 'history' in question only stretches back a few years, maybe a century or two. Only very occasionally, if the claim is truly deserved, does it strech back to the earliest era of written records. But now, with humanity's huge impact on the planet's climate becoming ever clearer, we need to go back several million years. Because climate-related news of history being made are about the level of atmospheric carbon dioxide (CO 2 ) reaching  400 parts per million  (ppm). The las