Thursday, May 13, 2010

Seth Roberts, wrong about doubting Climate Disruption Risk

Artist's rendition of Earth's magnetosphere.Image via Wikipedia
Wanted to highlight Phillip Price's responses to Seth Roberts, on the existence of human caused risk of climate disruption.

Seth Roberts, wrong about doubting Climate Disruption Risk:

Phil Says:  May 11th, 2010 at 12:26 pm

Seth, as you might imagine I disagree with almost everything you say here. But let me give just one example. You say:

“Here’s what I would consider reasonable evidence for serious human-generated global warming:

1. Temperature higher now than in the past.
2. Temperature increasing at a higher rate now than in the past.
3. Good (= verified) model shows serious human-generated warming.”

But in fact, neither of the first two would be reasonable evidence of serious human-generated global warming if they are true, and the absence of them does not indicate absence of serious human-generated global warming if they are in fact absent.

Here’s the key fact that you seem to be unaware of (but that scientists who study this know very well): MORE THAN ONE PARAMETER AFFECTS THE TEMPERATURE OF THE EARTH. It’s not all about carbon dioxide concentrations.

If high temperatures in the Medieval Warm Period were due in part to higher solar activity, then those temperatures don’t tell us much about climate sensitivity to CO2. So your point 1 doesn’t really make sense. The issue with point 2 is pretty much the same, except with regard to the derivative of temperature rather than temperature.

And for the models…you assert that the models aren’t good enough to estimate temperature sensitivity, but you’re wrong.

Yes, I know that scientists, like everybody else, tend to be overcertain. But I don’t think that means that nobody knows nuthin’.

I asked you before, more than once, to give YOUR estimate of climate sensitivity (defined as the steady-state change in global average over preindustrial levels in response to a doubling of CO2 over preindustrial levels). You still haven’t answered that question. But it seems that for some reason you put very little of your probability in the range that almost all climate researchers think is most likely. So who is being overcertain?

Phil Says: May 12th, 2010 at 2:55 pm

Check the IPCC report, chapter 8: there is an extensive discussion of climate modeling and why it is good enough to be sure that anthropogenic climate change is real and why the key parameters are likely to be not extremely far from the (admittedly wide) range of estimates.

But what I am taking issue is with much larger than your three assertions, though I think they are all incorrect.

You are criticizing people for being “overcertain” because their estimate of climate sensitivity has an uncertainty of “only” 6C, but your own estimate has less uncertainty than that, in addition to being centered much lower than the experts think is reasonable. I do not think you have any basis for having a narrower confidence interval than the experts do, and I do not think you have any basis for having a much lower central estimate than the experts do.

[ Edit 05/13/10; Michael Tobis weighs in ]

Michael Tobis Says:  May 13th, 2010 at 12:10 pm

To your first two points, there is nothing that says that warming has to be simultaneous with greenhouse forcing. Under present circumstances we in fact expect the contrary: the thermal inertia of the oceans and the masking of industrial dust mask the committed warming. So your proposed tests simply aren’t valid.

Also, climate models make effective predictions of many things, not limited to global mean surface temperature. As a particular point, they show and have shown since the 1980s that greenhouse forced warming is a near-surface phenomenon, accompanied by stratospheric (upper atmosphere) cooling. They also show a pattern of warming that concentrates on land areas in continental interiors. These long standing predictions did in fact emerge. So your claim that climate models are without skill are without foundation.

All of this is silly; it treats “global warming” as a falsifiable theory, a claim of a causation that is either true or false. This is foolishness. The underlying phenomena, (thermal radiation, absorbtion and reradiation in gases) is two hundred year old physics that is as well established as anything in science.

What’s at issue is not “whether” but “how much”. As Phil correctly points out, those who call themselves “skeptics” are not making an argument from ignorance, they are making an argument from certainty. If we really had no idea what the sensitivity was, we should be more concerned than ever. The attitude suggested by people who claim to be “skeptics” is utterly inconsistent with a lack of confidence in the underlying science. It is a claim that the the sensitivity is certain to be much less than all prevailing evidence indicates.

(Phil’s a bit pessimistic; I’d say the consensus range is 2 C to 4.5 C per CO2 doubling. )

And what if it were zero? Would we be out of the woods? No, even with a global sensitivity of zero we could have huge forced climate change, say, warming the poles and cooling the tropics. There is no doubt that the amounts of CO2 and other gases we are adding to the atmosphere change the way energy flows through the system, a system which at heart is fluid and easy to change. Even in the absence of knowledge and a low global sensitivity there are huge risks.

And then there is ocean acidification.

Sorry. We have to deal with this.

[ Edit 05/13/10; my comment added ]

Seth Roberts says:
seth Says: May 12th, 2010 at 2:47 pm
[...] I’ll provide you my confidence interval in a few days.
It will not be forthcoming.  This was all a predictable exercise in the Art of Controversy.  But it is good to document how these each can be swatted down with minimal effort.
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