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Thursday, November 7, 2013

Pat 'n Chip play with climate models at WUWT

Sou | 1:20 AM 2 Comments - leave a comment

Updated - See below to find out just how wrong Pat'n'Chip are.


Paul C. “Chip” Knappenberger and Patrick J. Michaels are at it again at Anthony Watts' blog WUWT.  I don't think anyone else would have them apart from some right wing rags.

They are claiming that the models are all wrong.  They said they used the model runs as provided on the KNMI Climate Explorer website.  So I went to Climate Explorer and just downloaded the data for RCP8.5 and RCP2.6 and compared it to GISTemp.  This is the result:

Data Source: NASA and Climate Explorer


You'll notice there's little difference between RCP8.5 and RCP2.6.  They don't start to diverge for a few more years.

Bearing in mind there are no error bars shown and that the errors in the observations increase as you go back in time, what strikes me is how darn close the modeled surface temperature is to the observations.

So then I went back to WUWT to see why Pat'nChip say the models are "all wrong".  They wrote:
But very few  people know that the same situation has persisted for 25, going on 35 years, or that over the past 50-60 years (since the middle of the 20th century), the same models expected about 33 percent more warming to have taken place than was observed.

33% more warming since the 1950s? Now that's not what the data shows above.  The observations are fairly closely aligned to the model mean.


Update

Here are two more charts.  I've started them at 1951 because Pat'nChip say that "over the past 50-60 years (since the middle of the 20th century)" the models expected 33% more warming.  That's balderdash as you'll see in these charts:

Data Source: NASA and Climate Explorer
Look at the above chart from 1951 to 2001.  The linear trend in the observations is almost indistinguishable from (and slightly steeper than) that of either of the two RCPs.  This completely contradicts the claim of Pat'n'Chip about the "situation has persisted" for last 50-60 years.

Next is 1951 to 2012.

Data Source: NASA and Climate Explorer

Over the period 1951 to the present, the trend for the models is slightly steeper than that of the observations. But certainly not by 33%! It's not even half that. The divergence is from around 2005 onwards.

End Update.


So what did Pat 'n Chip do?  They haven't compared the models to the observations directly.  What they did was this:
We’ve calculated the trend in the global average surface temperature simulated to have occurred starting in every year since 1950 and ending in 2012 for every* run of every climate model used in the new IPCC report. In Figure 1, below, we compare the average (and spread) of these 106 model runs with the observed trend during each of the same periods.
They say they calculated the trend in °C/decade, rather than plotting the straight temperature.  I've played with the data a bit but I can't get anything like their chart shown below. (click to enlarge):


I'm guessing they've smoothed the derivatives for starters. However I don't understand how they got such different rates of warming between models and observations.  If you compare it to the result in my first chart, the models and observations correspond well, particularly in the period from around 1930 to around 2004-05.  (The observations show more variation because the model plot isn't a single run, so any variation is averaged out.)

Maybe someone can help me out here and tell me how Pat 'n Chip calculated the rate of warming, and why it appears to be different to what I, at least, would expect.

2 comments:

  1. "They say they calculated the trend in °C/decade, rather than plotting the straight temperature." Call it the ruse it is again, solved. Tomorrow they will calculate the greenness of a grape and tell us it't global temperature.

    ReplyDelete
  2. Perhaps try HadCRUT4 as they did ;).

    Re Pat 'n Chip's underwhelming and boring effort: Of course they didn't mask the domain of the CMIP5 runs according to HadCRUT. Of course they selected 2012 as fixed end date rather than 1950 as fixed start date as every sane person would do. Of course they fail to mention that volcanic and solar forcing after 2005 isn't up to observations in the models (rather it is a projected forcing also with regard to natural variability, i.e. solar as in previous cycle and no volcanic eruptions). And of course La Nina only exists in the corrupted minds of government scientists. At least they labelled the chart with Cato Institute, which I would argue is the single most important information after all.

    ReplyDelete

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