In contrast to the sorts of results from “simpler models”, the spread around the multi-model mean in the AR4 represents the difference in means from individual AOGCMs and some internal variability that was not averaged out because there aren’t enough runs.

The choice of “line” in FAR is a function of climate sensitivity.

Really? Why are the FAR predictions so much higher than the SAR and onward when CS estimates have been essentially the same since the Charney report?

I still remember back at PNNL, one of my coworkers was working on a project that has a euphemistic acronym. Engineers and scientists had been referring to something as an “eruption”. The powers that be had gotten together with the editors, and dubbed it the “Glass Displacement Event” (GDE).

During a summer talk a summer student kept calling it the “GDE”. At the end of he talk, someone asked him what “GDE” stood for. The nervous student paused. Then someone in the back of the room said “The GOD DAMN ERUPTION!”

The “event” was soon renamed. . .

(BTW the event was this: A proposed process involved inserting electrical conductive rods into soil, heating the soil until it became molten, removing the rods and then letting the molten soil solidify. During one event a gas bubble formed, and violently spewed forth setting the protective tent on fire. Some carefully trained editors tried to convince people the word “eruption” did not apply to this because that only applied to volcanoes; the lined out every instance of “eruption” used in reports Showing examples like “pimple erupts” etc. left them unmoved. Glass Displacement Event, or the shorter “event” were dubbed “correct”.)

I think you mean FAR, not TAR. In general, climate science needs to be a bit less fond of acronyms. I once had a friend burst out laughing when I started discussing the IPCC AR4 WGI SPM.

As for the FAR, it didn’t include sulphate aerosols, right?

I already said that, if the only thing I had was that graph, I picked numbers off that graph, I’d pick the centerline and I’d explain that as my basis.

I think that’s what Roger means when he says what he did squares with what you report he said he did. He used the values associated with dots on the graph.

Meanwhile, the specfic value you quote are middle line– which Roger does not indicate with dots.

What’s confusing about Roger’s use of “square with”?

So, as I perviously said

I would probably have picked the dark green line in the center of the FAR scenarios, but Roger explained which he picked in that comment thread and illustrated how he got the number. He pulled it off the top line, not the center line. He mentions other numbers could be picked in the comments– and those correspond to the ones you are mentioning.

So, in short: Unless there is other information in the FAR itself, I would probably illustrate 1990 projections using the middle green line, you would have used the middle green line. Gavin would have used the middle green line. Roger picked the upper green line, said that’s what he did, and described that as being what he did and explained why he chose that.

Look at the dots and letters. That explains where he got it. He said so in comments.

This squares with the part of your comment you did not re-cite:

I don’t know what Roger’s dots are, as they appear to be on the upper bounds which makes no sense to me.

The original graph is on p. 69 of the AR4 TS, in section 5.1 “Understanding Near-Term Climate Change”.

Roger says “You’ll see that the values square with what was said in comments 15265 and 15266.”

The IPCC statement I cited in 15265 was:
“Projections for 1990 to 2005 carried out for the FAR and the SAR suggested global mean temperature increases of about 0.3°C
and 0.15°C per decade, respectively.”

From an examination of TS.26 I cited a value of 0.28 or 0.29 deg per decade. Or as Gavin put it, 0.45 in 2007, not 0.6.

The graph shows 0.34-0.35 for FAR so it does not “square with” my comment.

I have not “corrected” it because I have a different interpretation than you do on the 1992 scenarios. We have a difference of opinion. I won’t be so arrogant to suggest that you “correct” your thinking because reasonable people can disagree on such things.

As I pointed out to you, Figure A3.1 in that same report shows very large differences across scenarios prior to 2000, so I am not at all convinced that choice of scenario is irrelevant.

But even though I see things differently, perhaps you are right, and instead of 0.6 in 2007, it is something like 0.45. But as you imply, your point doesn’t alter the overall conclusions of the analysis — the IPCC dramatically reduced its predictions in 1995 (which it acknowledges explicitly). (And a point I do not raise, the 1992 FAR Supplement reduced the original predictions from 1990.)

So, a) he and Gavin seem to be discussing different scenarios and b) the choice doesn’t make a difference to the point Roger is making.

I would probably have picked the dark green line in the center of the FAR scenarios, but Roger explained which he picked in that comment thread and illustrated how he got the number. He pulled it off the top line, not the center line. He mentions other numbers could be picked in the comments– and those correspond to the ones you are mentioning.

But Gavin’s point (and mine) was and is that the slope was wrong – it should have been no higher than 0.3 deg C per decade, and probably slightly lower (looking at graph fig TS.26). As I said the correct value appears to be 0.28 or 0.29.

Am I missing something? I’ll be happy to retract if someone can point out my error.

http://sciencepolicy.colorado......cation.png

http://sciencepolicy.colorado......008.07.pdf

You’ll see that the values square with what was said in comments 15265 and 266. Deep Climate’s memory is mistaken or incomplete.

Does this mean that the next time someone says “it is worse than we thought”, they are speaking in direct contradiction to the IPCC findings, which show that earlier, less dramatic projections (TAR) have proven over time to be more robust than the later (AR4) more alarmist ones?