This "consensus" was obviously way premature, a bandwagon pushed by various agendas. There are good reasons to reduce carbon emissions and use of fossil fuels that do not require prostituting science. There is also a new film about to show on Britain's Channel 4 that presents the dissenting case; specifically, that global warming is due to the cyclical activity of the Sun, and that increases in CO2 are the result of that warming, not the cause of it. If I understand the argument correctly, much CO2 is stored in the oceans, and when temperatures rise more of that CO2 releases into the atmosphere.
Whatever the truth turns out to be, the eagerness of otherwise rational people to take 50- and 100-year climate predictions seriously ( about tenths of a degree!) has been highly amusing. Less funny is the willingness to entertain extremely costly responses, even though they promise to have little or no effect on global temperatures. It all suggests two things to me. First, that there are strong interests driving this that have nothing to do with climate change per se; second, that for a large percentage of people, science is just a modern form of magic.
The apostasy of a figure like Allegre contains a lot permission for others to jump ship. My prediction is that as others follow him down the gang plank, the core group of global warming true believers will become increasingly hysterical, determined to hold their fanciful consensus together. But those less committed will be concerned with saving face, strangely and suddenly silent as they furtively search for graceful ways to distance themselves, and to retroactively re-write their own role in the whole embarrassing mess. After all, if you want to keep the grant money and conference invitations coming, you need to keep that wet finger in the wind. There is some lead time involved, but I suspect that 18 months from now the tone and tenor of climate articles in the leading science journals will be different from what it's been lately.
Byron
