Hasbeen:- Is at again making assertions without any evidence just sling off at a scientist and hope the mud sticks.

I must be hard for you to accept that all the skeptic climate scientist accept climate change is happening and that man is making a contribution, all they are arguing about is the percentage and it may be something else without being able to show anything.

Geoff - I most certainly did talk about the substance of the paper. As I pointed out you cannot say it is wrong - that's impossible as its talking about a projection - just very weak because it is a projection which relies on several assumptions. You also have this problem in that there is some evidence that temperatures were a degree or two higher in medieval times and further back in the holocene, with no evidence that sea levels suddenly rose 5 metres.This business about temperatures now being as high as the MWP or the mid-Holocene maximum is a hard core global warmist thing.

None the less the paper has some scientific credibility in that it cannot be contradicted, but it remains very weak material. Take a step back and look at the paper for youself.

However, Hanson also has major political problems in that he is trying to insist on even tougher targets on emissions by relying on material that is much weaker than his earlier efforts with ice sheet break-up theories, which did not get the emission levels he wanted originally.

The global warming camp is becoming hysterical.

QUESTIONS

Thanks Geoff

1. "The Hansen & Makiko paper doesn't depend on climate modelling at all."

My modelling post was actually a response to your comment:"Weather is chaotic, but that doesn't make climate (the long-term average) chaotic."

I ask again: "Are you are claiming "long-term climate" is predictable? On what basis? Computer models? Established laws of climate change?"

In your post below you seem to endorse what "the climate modellers are concluding"?

"They are taking advantage of a natural experiment, conducted by the Earth, with all the complicated physics included and fully accurate - things like moisture levels and cloud formation. It allows the "climate sensitivity" to CO2 to be extracted. The result is that CO2 doubling from present levels will produce a temperature increase of 3 degrees, global average. Strangely enough that is about what climate modellers have been concluding. Without the CO2 feedback, the ice-age variations would have been only about 1.2 degrees."

2. Are you seriously suggesting that proxy data from the distant past (about "a natural experiment by the Earth") gives a complete and "fully accurate" reconstruction of a past climate with sufficient integrity to allow confident causal conclusions about "climate sensitivity" to carbon dioxide at that time?

Alice (in Warmerland)

Alice-
1. It is a characteristic of systems exhibiting "deterministic chaos" that they fluctuate chaotically about a mean that is fairly steady. Weather is chaotic, and its fluctuations are intrinsically unpredictable more than a week or so in advance, because the inevitable uncertainties in our knowledge of present conditions amplify exponentially with time in a chaotic system.

The slower evolution of the mean is not subject to this limitation. So, paradoxical as it might seem, climate (the slowly evolving mean) is more predictable than weather.

Can climate models usefully project future climate? Well, it's not easy, and there are some major uncertainties and difficulties, but they are not as hopeless as many denialists claim. For one thing, the projections have been fairly consistent over time, even though the early models were extremely simple in comparison with current ones. For another the real climate has developed broadly in accord with earlier projections, a basic fact that deniers overlook. FInally, the projections are consistent with estimates derived entirely independently, such as Hansen and Makiko's extraction of climate sensitivity from records of the past.

2. I'm not suggesting that the past climate can be reconstructed "fully accurately". I said the physics was in the real climate with full accuracy. Nor am I suggesting "confident casual conclusions". I am suggesting reasonable conclusions based on reconstructions whose uncertainties have been limited by a lot of past work on how to interpret proxies.

You see, real scientists openly discuss uncertainties and difficulties, and look for ways to reduce them. One way is to find alternative, independent ways to answer questions. If such independent approaches yield compatible conclusions, that builds confidence that the approaches are on the right track.

Too often, denialists take the discussions of uncertainties out of context and portray them as discrediting everything the scientists are doing. Then, if scientists reach a conclusion that the data seem to support, denialists say they must have fudged the data, or the analysis of the data, as our friend Curmudgeon seems to be doing.

UNCERTAINTY

Thanks Geoff

"You see, real scientists openly discuss uncertainties and difficulties, and look for ways to reduce them."

If only "real" climate scientists (and the IPCC) had taken your advice, openly discussing their uncertainties and difficulties transparently and honestly under rigorous public scrutiny rather than being, or appearing to be, complicit in (among other things) driving a UN "climate debt" agenda, perhaps there would be less doubt about their "storylines" today?

As one prominent climate scientist lamented recently: "apart from the issue of the actual logic used for reasoning, there is circularity in the argument that is endemic to whatever reasoning logic is used. Circular reasoning is a logical fallacy whereby the proposition to be proved is assumed in one of the premises.

http://judithcurry.com/2010/10/24/overconfidence-in-ipccs-detection-and-attribution-part-iii/

Another emphasised "the communication of climate projections, their uncertainties and caveats is crucial, and certainly merits more attention."

A critique of the IPCC’s treatment of uncertainty by the InterAcademy Council in October last year rightly noted (page 35, chapter 3) that: “assigning probabilities to imprecise statements is not an appropriate way to characterize uncertainty. If the confidence scale is used in this way, conclusions will likely be stated so vaguely as to make them impossible to refute, and therefore statements of ‘very high confidence’ will have little substantive value.”

By the way, is using an offensive term like "denialist" to label those who disagree with you either justified or helpful?

Alice (in Warmerland)

"By the way, is using an offensive term like "denialist" to label those who disagree with you either justified or helpful?"

Tis but a tool to help remind himself of his own superiority when dealing with anyone who disagrees .. hubris.