To be more complete in sourcing the inputs for the climate models, I should have noted that the mystery behind the unexplained changes in atmospheric methane concentration trends should be attributed to a third source/discipline that would fall outside the area of climatology or at least that area that uses inputs to predict future climates. I am not sure about how well the fluorocarbon concentrations followed predictions/projections after the Montreal protocols, but certainly these predictions fall into an area other than climate and economic modeling.

Again I say it is not very productive to analyze the Hansen A, B and C scenarios without evaluating all these parts separately. The biggest question would appear to be the evaluation of the Hansen climate modeling as we have a better view of the GHG actuals versus prediction and would have to give pause to any great confidence there.

I would think that one must look long and hard as to why Scenario A was used at all if it did not have some basis in a future reality for those doing the predictions. The only other conclusion one could draw would be that an unrealistic scenario was being used to push climate policy.

Another factor in the climate modeling that bothers me is the acknowledged lag effects and how would one realistically line up the changes in GHG concentrations and temperature anomalies. If the models say that the system has a momentum of X degrees anomaly for existing GHG levels than when some here say we have to give Hansen credit for predicting a temperature increase would that credit not be a more general one dealing with the lagged effects.

So far, I’ve been unable to identify material differences in the Scenario A and Scenario B forcing over the 1987-2007 period that account for the difference in temperature between Scenarios A and B.

I wonder if part of the solution is that the model estimates a final delta T based upon the cumulative changes in GHG concentrations and then interpolates the steps required to achieve the estimated end point or milestone?

Re: #72 and #73

There may be something to this. It could be that the work ethic of the committe (or at least some of the committee members) which demands that they produce as much paper as possible to justify their existence (and all that goes with that).

Steve: Please note that subsequent to this, I’ve pinned down the difference to the handling of Other CFCs.

But don’t the long term climate predictions depend on economic predictions?

Long term climate predictions, when made as scenarios, depend on inputs into climate models and those inputs depend on economic predictions, but accuracy of the climate part of those predictions/scenarios depends solely on how well climate is predicted for any set of variable inputs. That’s the whole point of the arguments I have made and I have heard Pielke Jr make many times and that is one needs to separate these predictions/projections in order to determine the accuracy of either and both parts. Pielke has said, in effect, that predicting the correct temperature changes out-of-sample using a set of inputs that does not match the scenario used should not give any amount of good confidence in the climate part of the scenario (or the economic/input part of it either).

I would predict that in some distant time it will shown that climate predictions are by nature less difficult to make with a given certainty than economic predictions.

But don’t the long term climate predictions depend on economic predictions?

At that time the Montreal Protocol hadn’t even been signed never mind implemented.
Regarding Methane we still don’t know why the previously steady growth rate changed in ‘92 so that would be rather difficult to project in 87!

My point has been not to blame the projectors but to emphasize how difficult it is to predict the emissions of GHGs and those predictions are every bit or more important to the scenarios than projecting the climate part of the scenarios. Why not for the sake of analysis separate the two parts of the scenarios since those parts must necessarily come from very different sources and disciplines?

While economics may be better versed in the statistical applications necessary for that discipline (as compared to climate science) it has not established a very good track record in making predictions. And I think that it is difficult by the very nature of economics. I would predict that in some distant time it will shown that climate predictions are by nature less difficult to make with a given certainty than economic predictions.

In answer to somebody’s question; yes, they get paid by the page.

Typical of the slander that regularly pops up on this site.

Steve: Bugs, is this your idea of a useful explanation of the methane concentrations:

The reasons for the decrease in the atmospheric CH4 growth rate and the implications for future changes in its atmospheric burden are not understood (Prather et al., 2001) but are clearly related to changes in the imbalance between CH4 sources and sinks.

Can you point to anything more illuminating than this in AR4? Do you think that the A2 or A1B methane projections make sense? Can you point to a valid scientific justification? I’m asking – I don’t know this literature.

It seems likely that those politicians who have ready the main WGI reports are the ones questioning “the” “warming” and holding panels and trying to figure out what’s really going on.

The ones that most support “doing something” and talk about a “climate crisis” either haven’t ready the WGI stuff, or have read it and have an agenda (or aren’t intelligent enough to understand it).

In answer to somebody’s question; yes, they get paid by the page. I’d guess if everything was written more directly (while still being professional of course; they’re not exclusive) you could very likely get rid of 90% of the material.

You don’t think that stuff is written that way by accident, do you? Part of it is the culture, part of it is the career and its writing style, part of it is the group process of compromise and how the writers and reviewers interact, and part of it is the mandate and agenda of the IPCC itself. Throw in some inertial, some pride, the political aspects of the participating agencies the writers work for, and the unstated assumption that the anomaly trend=warming.

Bake it in the oven for 2 hours at 400 F.