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« Parched earth policy | Main | In the news today - Josh 370 »
Saturday
Apr232016

Gav loses it - Josh 371

When Steve MicIntyre writes "In the past few weeks, I’ve been re-examining the long-standing dispute over the discrepancy between models and observations in the tropical troposphere." you might think you were in for a bit of a technical post - which, of course, it is - but it is also also very funny and well worth reading. It also inspired the cartoon below.

Click image to enlarge

H/t commenter 'See owe to Rich' for the 'hide the gap' phrase.

Cartoons by Josh


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Reader Comments (155)

I've already explained several times to you Phil, it's like plotting GISTEMP on a 1951-1980 baseline, then plotting the exact same graph on a 1981-2010 baseline, and getting confused as to why the data point for 2015 is at a different point on the Y-axis on each graph

That is precisely what Gavin wanted to demonstrate.

May 13, 2016 at 9:12 AM | Unregistered CommenterPhil Clarke

There's also the wee point that Gavin is plotting the same thing, with shifted baselines to illustrate, um, the effect of shifting baselines. This is legitimate and useful.

The long and tedious comparison between the 'climate lab book' graph and Christy's graph is comparing Christy's temperatures in the tropical troposphere with the global surface temperatures.

I pointed the CLB chart as a exposition of the combined effect of Christy's cherry picks. To try and compare across the two while ignoring all the cherry picks but one is indeed to compare apples and oranges.

'F' for comprehension.

May 13, 2016 at 10:04 AM | Unregistered CommenterPhil Clarke

Have you considered the possibility that the start point of Gavin's baseline periods is being set by the start of the satellite data and by what Christy chose to do?

Not got time to respond at the moment, but all he showed is that if you put anomalies at a different baseline you get a Y-axis shift. So what? Both baselines are valid, and have similar spread.

As I explained, if you align the X axis to a common baseline, after 20 years the constant radiative forcing embedded in the models makes them overlap almost exactly. I show this in an animation I put on twitter here:

Twitter link

As I show, both baselines yield pretty much identical spread and Y-axis position in the regions that matter, as long as you use a sensible abscissa (i.e., the time after the models and observations are forced to converge).

I'm sure you'll all be glad to know I'll be offline for the next week or so. Have fun!

May 14, 2016 at 12:34 PM | Unregistered CommenterSpence_UK

Spence,


Not got time to respond at the moment, but all he showed is that if you put anomalies at a different baseline you get a Y-axis shift.

No, he didn't. Try reading it again, this time with your eyes open.


I'm sure you'll all be glad to know I'll be offline for the next week or so.

I genuinely don't care, one way or the other.

May 14, 2016 at 12:41 PM | Unregistered Commenter...and Then There's Physics

Gavin

Historically, Christy and Spencer have use single years (1979) or short periods (1979-1983), however, in the above graphs, the baseline is not that simple. Instead the linear trend through the smoothed record is calculated and the baseline of the lines is set so the trend lines all go through zero in 1979. To my knowledge this is a unique technique and I’m not even clear on how one should label the y-axis.

Using the case with the decade-long baseline (1979-1988) as a reference, the spread in 2015 with the 1979 baseline is 22% wider, with 1979-1983, it’s 7% wider, and the case with the fixed 1979-2015 trendline, 10% wider. The last case is also 0.14ºC higher on average. For reference, the spread with a 20 and 30 year baseline would be 7 and 14% narrower than the 1979-1988 baseline case.

Its spread, rather than a simple translation up or down. But hey, this is a guy who cannot tell global with tropical, troposphere from surface and a single scenario from a range.

'F' for comprehension, 'U' for humility.

'A' for arrogance though.

May 15, 2016 at 1:43 AM | Unregistered CommenterPhil Clarke

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