Inspired by Gareth, I couldn't resist:
Q: How many climate sceptics does it take not to change a light bulb?
A: Approximately 100. 1 to say that the current absence of light is the result of natural solar cycles and the other 99 to disseminate this finding through their 'science organisations' and oil industry funded think tanks.[Update: This is cool. Robert Butler, the author of the original climate change light bulb joke has blogged about the spread of the meme, very kindly stating that my own humble attempt above is his favourite derivative thus far. Thanks Robert!]