Here is a comment that I left on this post at Deltoid:

“I might be missing something here, but shouldn’t the green line and the blue line start from (approximately) the same place at the time of prediction? I’m assuming that the IPCC line starts from some sort of climate average – then the Ridley predcition should do that too.

Otherwise, this is just the same wheeze of choosing a convenient starting point to make your opponent’s prediction look bad, as we have seen elsewhere.”