Bjorn Lomborg's new book, Cool It! is getting less than sympathetic reviews from those whose job it is to understand climate science. No surprise there. But here's a review by an economist, in Nature no less. Given that Lomborg approaches the question of what to do -- and what not to do -- about climate change from a conventional cost-benefit perspective based on the advice of economists, including four Nobel laureates, the Nature review is devastating.
The review is behind a subscription wall, so here's the money paragraph:
Unfortunately, Lomborg's thesis is built on a deep misconception of Earth's system and of economics when applied to that system. The concentration of CO2 in the atmosphere is now 380 p.p.m., a figure that ice cores in Antarctica have revealed to be in excess of the maximum reached during the past 600,000 years. If there is one truth about Earth we all should know, it's that the system is driven by interlocking, nonlinear processes running at different speeds. The transition to Lomborg's recommended concentration of 560 p.p.m. would involve crossing an unknown number of tipping points (or separatrices) in the global climate system. We have no data on the consequences if Earth were to cross those tipping points. They could be good, or they could be disastrous. Even if we did have data, they would probably be of little value because nature's processes are irreversible. One implication of the Earth system's deep nonlinearities is that estimates of climatic parameters based on observations from the recent past are unreliable for making forecasts about the state of the world at CO2 concentrations of 560 p.p.m. or higher. Moreover, the nonlinearities mean that doing more of a bad deal (Kyoto) may well be very good.
Now, I am not sure that I know how the reviewer, Partha Dasgupta, a professor of economics at the University of Cambridge, determined where the tipping points are exactly. Figuring that out continues to challenge the best of the climatologists. Jim Hansen says only that he suspects we're really close to one or more. Tim Lenton makes an honorable stab, but acknowledges we need lots more data before we can know with any decent degree of confidence.
Having said that, though, 560 p.p.m. may well be on the far side of a fair number of thresholds we really shouldn't cross if we know what's best for us. So I'm nitpicking. The review is, on the whole, and as I said, devastating.
- Log in to post comments
I'm very doubtful of tipping points.
There are various reasons.
Firstly, a tipping poing is a non-linearity, and that means some form of positive feedback. We know from the very long term record that these are very rare. The only examples I know of are the transition to an oxygen rich atmosphere and the melting of snowball earth scenarios. Each with a well know reason for the transition.
The long term historical CO2 record shows levels 500% above the current record without the earth suffering major changes.
If there were a tipping point for CO2, we would have had it already, and life wipped out etc. Since we are here writing about it, the tipping point doesn't exist.
Nick
Nick, How long ago was it that the earth had 500% more CO2 than present? The sun is becoming more luminous by about 6% per billion years. A doubling of CO2 forcing is equivalent to roughly 1.7% (if I remember the number right) solar intensity increase. So roughly speeking we need half the CO2 today as 270mya to have the same forcing.
Of course continental positions etc have changed also, long past conditions can only provide a little bit of reassurance.
In any case, I think the climatologists are talking about less catastrophic tipping points, such as the snow/ice/vegetation albedo effect that has probably crossed a tipping point in the arctic, or
changes to a new oceanic circulation state. These are unlikely to make the planet uninhabitable, but the adjustment to them could be very expensive.
The fact that life doesn't die out entirely when environmental conditions change is not a good argument to make -- as various minor disturbances have shown (the dust bowl, droughts in sub-saharan africa, the Little Ice Age) what we like to think of as civilized life appears to require really quite a narrow range of conditions. (Some people may be willing to see 10-50% of the human population go away as a result of climate change, but almost all of these people manage to believe that they won't be part of the losing fraction...)
Can any of you gents direct me to a reference for an estimate of the effect of the Permafrost biomass waking up and putting out Methane?
Dear Mr. Hrynyshyn,
Yesterday a colleague drew my attention to your piece, dated 13 September. It's finely written, but contains one misreading of my review of Bjorn Lomorg's recent book on the economics of climate change. Nowhere in my review do I say I know where the climatic tipping points are. Indeed, I stress the uncertainties that plague experts' understanding of Earth's system. However, from studies of highly non-linear processes, one can be reasonably certain that tipping points exist, even while not knowing how many exist or where they are located.
Yours sincerely,
Partha Dasgupta