It is now more than 200 years since the great astronomer William Herschel observed a correlation between wheat prices and sunspots. When the latter were few in number, he noted, the climate turned colder and drier, crop yields fell and wheat prices rose. In the past two years, sunspot activity has dropped to its lowest point for a century. One of our biggest worries is that our politicians are so fixated on the idea that CO2 is causing global warming that most of them haven't noticed that the problem may be that the world is not warming but cooling, with all the implications that has for whether we get enough to eat.