A RESPONSE TO ANDREW REVKIN

Dear Benny

For once, I shall leave Andrew Glikson's wild world of bizarre linear extrapolation to others and focus on the new challenge from Andrew Revkin: "A question for climate skeptics: I presume you agree there's at least a chance you could be wrong, just as you assert those pointing to a clearcut climate apocalypse have little basis for their claims. On that front, I'd be curious to know what you'd propose as a backup plan if the climate's sensitivity to CO2 turns out to be higher than you think?" This is such an interesting question that I'd like to throw this open to CCNet's entire readership:

Where is the empirical evidence that the earth's climate has any measureable sensitivity to carbon dioxide rise? Theoretically in an equilibrium situation carbon dioxide rises should cause warming. But then we're not in an equilibrium situation.

Personally I am baffled by calculations of "climate sensitivity to carbon dioxide" which ignore the fundamental problem that all reconstructions of carbon dioxide versus temperature from ice cores show that temperatures rise first and then centuries later carbon dioxide (and that other dread GHG methane) begin to rise. Even while carbon dioxide continues to rise , the previous started warming proceeds at the same rate, and then stops abruptly and begins a relatively slow decline. I am baffled because of two things:

1. How can supposed cause or even amplification of temperature rise by carbon dioxide induced warming be deduced from this behaviour which is the reverse of that assumed in greenhouse theory?

2. If the ice core records are correct about the amount of carbon dioxide in ancient atmospheres being lower than today's value (which in itself opens a whole new can of worms about ice core sampling), and given that the theoretical response of temperature rise to carbon dioxide rise is logarithmic, why don't any ice cores show any sensitivity to carbon dioxide at lower levels when the sensitivity should be much higher?

I ask these questions genuinely openly without sarcasm. Which brings me to Andrew Revkin's question: Andrew Revkin assumes that "climate skeptics" are a priori biased for some reason unable to see the marvellous truth of greenhouse gas theory, but why should anyone believe in a theory for which there is no empirical evidence? What if we've all been steamrollered into accepting a hypothesis of "climate sensitivity" to carbon dioxide which is false? If the sensitivity is even higher, as Andrew Revkin asks us to consider, why has this never been seen in the past when amounts of carbon dioxide were much lower?

So first, before too much else happens, before we invent fantastical geo-engineering schemes to manage the Earth's climate, will someone explain what is the climate sensitivity of carbon dioxide rise eight hundred years hence upon the temperature rise of today? sincerely

John A