You can find yourself feeling sorry for UK home secretary Alan Johnson, currently embroiled in a messy fracas with his own former scientific advisor on drugs. In the rough and tumble of  pre-election politics, an evidence-based drug policy which advocates the downgrading of the status of cannabis and ecstasy can become  kind of inconvenient.

It’s not hard to imagine a similar situation arising with climate change.

Maybe it already has.

When the government’s former chief scientist Sir David King said back in 2005 that atmospheric carbon dioxide levels needed to stabalise at the level of 550 parts per million there were activists and scientists who were shocked at how high he’d pegged the figure. David King later explained that it would be “politically unrealistic” to demand anything lower.

Sir David King clearly had a better understanding than the sacked Professor David Nutt of what constitutes “science” in the political context.

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