I have seen the film of Al Gore last week and followed a debate about it from a housewive here who managed to invite over 1,000 politicians to see the film (yes we have so many politicians in our federation: 1 king (and a lot of relatives), 3 language areas, 4 governments with near a hundred ministers and alikes, with overlapping federal and state authority. No worry if you don’t understand it, we don’t either! But somehow it prevented Balkan-like civil wars…). She was invited afterwards by the federal minister of environment to do the speach for Belgium at the Nairobi Climate Conference. It was all by all a quite emotional letter (and debate). In the debate, I said that I could follow the second part of the film (how to reduce our dependence of fossil fuels), but that I had a lot of problems with the “science” of the first part. The journalist on duty called it “a high Hollywood content”, which describes it very well.

In the film I noticed many untruths, half truths (by omitting relevant information) and exaggerations. To name the most important:

- Mann’s hockeystick as proof that the MWP was cooler than today.
I suppose that this needs no more explanation here.

- The disappearence of the Kilimanjaro glacier.
The graph of historical temperatures based on the ice core of Kilimanjaro itself shows a warmer 9th and 14th century.

- The increase of tropical storms (and/or intensity).
More than enough discussed on these pages. No increase in number of storms, a small increase in the highest categories. Much depends on the accuracy of historical storm intensity. 2006 seems to be a very calm year.

- The New Orleans disaster.
The problems with Katarina don’t have anything to do with global warming, everything with the fact that the dikes around New Orleans were not high enough to widstand any tropical storm surge (the center of Katarina landed over Mississippi, not over Louisiana).

- Increased property loss from storm disasters.
That there is increased damage is clear, because more people live now in vulnerable habitats, just have a look at the number of Florida inhabitants a hundred years ago and now.

- Pictures of glaciers in the Alps.
The Alps have been nearly glacier free several times in the past 10,000 years. Several passes which still are closed today were open in Roman times (Col d’Hérens, Sustenpas).

Connection between CO2 and temperature in ice cores over the past 600,000 years (very suggestive performance by Al Gore!).
The temperature caused the change of CO2, not the reverse. CO2 changes followed temperature changes with hundreds to thousands years delay, be it with an overlap. But there is one period where the temperature decreased until a minimum, before CO2 levels started to decrease (the end of the Eemian). The subsequent decrease of 40 ppmv CO2 had no measurable effect on temperature. This points to a small effect of CO2 variations on temperature.

The melting of Antarctica:
Some parts (mainly the Peninsula) are melting, other parts are increasing (the eastside), in general it is in equilibrium.
Greenland melts now more at the edges than it increases at the top. Summer temperatures of Greenland nowadays still are lower than in 1930-1945, when the edge melt was faster, before GHGs did have much importance.

The North Pole did melt during the MWP more than today. From a recent publication in the Journal of Geophysical Research (14 April 2006):
“The degree of summer melt was significantly larger during the period 1130-1300 than in the 1990s”.

What Gore did, was very suggestive, but a little “economical with the truth”… And indeed the comparison with snake oil salesman (and TV preachers) comes into mind…

What on earth does this mean? “transient response’ over what time period?

Lee: do read the link I provided. You’ll understand how Raper et al define transient climate response in the context of their figure: “at the time of CO2 doubling at year 70, the 20-year average (years 61 to 80) global mean temperature change.”

In a more general sense, transient response is by definition a response not yet completed at any given time. For example, in 2005 we can postulate that the TCR is the part of ~0.7C attributable to GHG increases. Perhaps 0.4C?

As for the 7-fold increase I mentioned, 3C/0.4C = 7.5. My apologies if this arbitrary number caused you any confusion.

Temps have increased roughly 0.6C over the last 50 years. Whan does that stop being “transient’ and become “final?’

I don’t know when the final response to CO2 doubling would be realized. Do you? I’m just trying to understand how you can have such a big confidence in the IPCC sensitivity range. But we’re not making much progress so far.

If you had made this argument after the first 16 years or so of the 50 year period, with a temperature increase of about 0.2C, you would be claiming that we can only get an increase of 0.4C to “final’ temperatures.

No. In 1972 we didn’t have the equivalent of a 3/4 of effective CO2-doubling so I couldn’t make the argument I am making. OTOH, in 1972 the global temps had been decreasing for almost 3 decades, so it would be difficult to make much sense of the 0.2 figure you mention, if available at the time.

You are assuming without stating so that the “transient’ is over.

Am I really? But I am saying that we still have 20-25% GHG increase left to reach a CO2-doubling (?).

Do the scenarios depend critically on estimating the GHG atmospheric concentrations and to a lesser extend on predicting the occurrences and intensities of volcanic eruptions?

Is the skill in Hansen’s predictions determined exclusively by how accurately the computer can take these variable inputs and predict temperatures or does it include estimating accurately the GHG levels and volcanic eruptions?

If one agrees that the prediction includes the GHG and volcanic variable estimations then Hansen has failed, since Scenario A (exponential extrapolation from the 1970s) the GCG climate forcing levels were hugely overestimated and no volcanic eruptions were included, Scenario B (the conservative projection without significant GHG regulation with a linear extrapolation) overestimates the GHG forcing levels and by significant amounts and does include a very large volcanic eruption with an extent not quantified, and Scenario C includes predicting, evidently, some very stringent GHG regulations that has not occurred.

If one says that the models skills are relegated first and foremost to how well it uses variable inputs to predict temperatures, then one needs much more information about the inputs Hansen used and a test that would be run (out-of-sample) in an entirely different manner. It is under these conditions of testing that I believe Willis E points would be more validly applied.

The actual way the scenarios were set out (and measured) makes it obvious to me that it was done with policy advocacy more in mind that doing more exact science on testing the skill of 3D climate models. While Hansen did publish these scenarios in 1988, here, it is important in such evaluations to also determine whether other model outputs were published by Hansen and/or his associates around that time and to compare how well they performed out-of-sample.

Michael Kliphuis, Frank Selten & Henk Dijkstra Technical Report Dutch Computing Challenge Project Simulation of extreme weather events present and future December 15th 2004
http://www.knmi.nl/onderzk/CKO/Challenge/Techrep_DCCP.pdf
Dutch Challenge Project
http://www.knmi.nl/onderzk/CKO/Challenge/

“2) Even the models with the highest sensitivity only reproduce a roughly 2-fold increase from transient to final response due to thermal inertia. None of them produces a 7-fold jump, as a climate sensitivity of 3C would demand.”
—
What on earth does this mean? ‘transient response’ over what time period?

Temps have increased roughly 0.6C over the last 50 years. Whan does that stop being ‘transient’ and become ‘final?’

If you had made this argument after the first 16 years or so of the 50 year period, with a temperature increase of about 0.2C, you would be claiming that we can only get an increase of 0.4C to ‘final’ temperatures.

Much of he argument is about the rate of increase during the transient period – which in turn means the time it will be going on. You are assuming without stating so that the ‘transient’ is over. The fact is, because we don’t know the time constants (although we know that many are on the order of decades or longer, and they are being investigated and modeled), you can NOT make the argument you just made – because you cant know how much of the ‘transient’ we have observed yet adn how much is still to come.

Andronova, N., and M. E. Schlesinger. 2001.Objective Estimation of the Probability Distribution for Climate Sensitivity, J. Geophys. Res., 106, D19, 22,605-22,612 http://crga.atmos.uiuc.edu/publications/Objective_Est_dT2x.pdf data: http://crga.atmos.uiuc.edu/publications/Climate.html

In my first post I did mention the masking effects commonly alleged to explain this conundrum. However, I have another big logical problem with the sulphate aerosols cooling theory. If these aerosols are only short-lived and basically a northern hemisphere phenomenon, why was the mid-20th century cooling global? In fact, the southern hemisphere, where they had little to no effect, cooled more than the NH in that period: http://hadobs.metoffice.com/hadcrut3/diagnostics/hemispheric/difference/

If one looks at Hansen’s ‘predicted’ period, from 1988 when he presented his scenarios to present, one gets a decadal trend for scenario B of 0.19C/decade. During that same period, the GISS station data yields a decadal trend of 0.19C / decade, and using the observational global land-sea data from Hansen’s PNAS 2006 yields a decadal trend of 0.21C.

For the last year of the “prediction”, the GISS station data temperature lands slightly above Scenario B temps in 2005, while the land-sea temps are slightly below – both are within a few hundredths.

This latter point is the one you originally disputed when you posted your CA article, the one where you made the temperature offset relative to the Hansen alignment. To do so, you ignored the 50 years of calibration data that Hansen used to set the baseline, and aligned to the single year, with El Nino real-world temps (ie well above average for that year) with the slightly below average model results for that year. In doing so, you threw away all but one year of the 50 year calibration period run under initial conditions (ie 98% of the calibration data) and introduced a substantial amount of annual variation, all acting in one direction.

Hansen did not run that 50 year calibration period to ‘end up’ with the single best year – unforced annual variation mean that there IS NO single best year. He did it to get 50 years of data under the same conditions, and then he took the average, so that he could minimize the effect of unforced annual variation. Your approach maximizes the impact of unforced annual variation in the one year you chose. Stop pretending you haven’t heard this – it is precisely the point I as making when you dropped that argument and moved to the ‘trend’ argument.

Finally, you are continuing to mischaracterize what Hansen said, in ways that do not reflect well on you. Here is an extended quote from the PNAS 1996 paper – you would do well to read this carefully:

“”Because of this chaotic variability, a 17-year period is too brief for precise assessment of model predictions, but distinction among scenarios and comparison with the real world will become clearer within a decade.
Close agreement of observed temperature change with simulations for the most realistic climate forcing (scenario B) is accidental, given the large unforced variability in both model and real world. Indeed, moderate overestimate of global warming is likely because the sensitivity of the model used, 4.2C for doubled CO2, is larger than our current estimate for actual climate sensitivity, which is 3 +- 1C for doubled CO2, based mainly on paleoclimate data. More complete analyses should include other climate forcings and cover longer periods. Nevertheless, it is apparent that the first transient climate simulations proved to be quite accurate, certainly not “wrong by 300%”.

That is not a claim of model skill. Simply out, he is saying, “we cant know yet, we know there must be some problems, but so far,despite what soem are saying, there is nothing in that data to say the model is wrong by much.” That is a substantially different thing from the claim you are putting in Hansen’s mouth.