Sir, Robert O'Sullivan complains complains that the "save the planet" squadron only quote from scientific sources with which they agree. He himself does not quote from any scientific source, the best he can manage is a quote from Homer Simpson. What else can he do? The only explanation for climate change that has stood up to scrutiny is that it is caused by man-made emissions of greenhouse gases. It's a pretty simple. Greenhouse gases trap the heat of the sun and humanity is pumping out greenhouse gases like never before, while at the same time slashing and burning the forests that might have soaked them up. If you do the calculations based on what have burnt and what the Earth can absorb, it all fits with what we observe in reality. The few other explanations that have any scientific basis at all have been debunked. Every now and then someone puts forward a new possible cause, frequently with much media coverage. Then over the course of a few months the results are analysed, mistakes are found and the idea is put to rest. Of course the debunking never gets the same news coverage. There have been "natural" climate changes in the past but this time around we have a smoking gun and a bullet wound - declaring it to be "natural causes" would require some extraordinary evidence and that evidence simply has not been found,Update: Published without my reference to the media's lack of interest in debunking theories and some other minor tweaks. Update: Another round, although I don't think he actually read my letter!