Over the last five years there’s been a revival of an old hypothesis which suggests that the motion of the planets around the Sun modulates its output, and that variation in the Sun’s output affects the Earth’s weather and in the longer term, shifts in regional and global climate. This revival has been most visible here in the blogosphere, where ideas can be kicked around with less professional reputational risk, and a faster exchange and development of concepts and narratives can take place. There has also been a steady trickle of papers published in the scientific literature relevant to the theory, and these have been championed and denigrated by bloggers on both sides of the issue.
Naturally, in the overheated atmosphere of the climate debate, the second part of the idea is especially controversial, with the Intergovernmental Panel on Climate Change telling us that human emitted ‘greenhouse gases’ are the primary driver of global warming since the middle of the last century. They also say the Sun’s variation has very little effect on climate change. An IPCC author recently took exception to our special edition on the theory and got the journal we published it in axed. The first part of the idea is controversial too, as the received wisdom from most mainstream solar physicists is that the planets are too small and too far from the Sun for their motion to affect it. They are sure that the Sun runs an internal ‘dynamo’ (Babcock & Leighton) and ‘chronometer’ (Dicke) which accounts for the observations of its cyclic variations that have been made over the centuries.