Troy's Scratchpad

December 1, 2011

Katsman and van Oldenborgh 2011 Update

Filed under: Uncategorized — troyca @ 8:32 am

Two months ago I posted on a couple issues I had with Katsman and van Oldenborgh 2011: 1) They assumed overlapping 8-year trends were independent when calculating the likelihood of a single 8-yr negative or 0 trend occurring in the upper ocean heat content over 30 years, and 2) The ENSO observations did not support the theory developed by the model that El Nino was the cause of the extra radiation escape.

Thanks to commenter Howard on that thread, who pointed out that a correction has been published soon after (readable draft version), I am pleased to see that issue #1 was addressed.  The probability of an 8-yr negative trend (according to the ECHAM-MPI model) during that 30 year period starting in 1990 has been appropriately reduced from 57% to 25-30%, and the probability of a 9-yr negative trend has been reduced from 48% to 5-15%.  However, it appears the 9-year trend will now likely be positive, given the recent uptick in UOHC.   I would love to flatter myself and think I had something to do with the correction, EXCEPT that the draft was received by GRL on September 29th, a couple weeks before my post.

Finally, KO (2011) mention the following:

The computational error has no impact at all on the analysis in the remainder of the paper, from which we concluded that such a period without upper ocean warming is explained by increased radiation to space, largely as a result of El Nino variability on decadal timescales, and by increased ocean warming at larger depths, partly due to a decrease in the strength of the Atlantic meridional overturning circulation.

Bold mine.  As I pointed out in that previous post and in the 2nd issue above, their model suggests that 8-yr average El Nino conditions with a four year lead would explain part of the negative trend, but the ENSO index was actually negative in that four year lead to the current flattening.  It may be that El Nino variability is the cause, but if that’s the case then the ECHAM-MPI model would seem to have the radiative response to El Nino wrong (at least with respect to the time lag).  This, I think, would affect the conclusions.

2 Comments »

  1. Hey Troy…

    Not sure if you’re interested, but I had written an R program to go through ARGO and AR4 model nc files. In my case I was mostly interested at looking at annual temperature variances by latitude and depth:

    https://sites.google.com/site/climateadj/ocean_variance

    The source code linked at the bottom contained a function to retrieve the data based on latitude, longitude, depth, and time. Maybe that would be of interest to you if you were doing OHC calculations. Although the link above was for a variance analysis, the program can be relatively easily modified to calculate other metrics as well. For instance, as an after thought, I generated plots on ARGO temperature and salinity trends as well:

    https://sites.google.com/site/climateadj/argo-analysis

    Perhaps you have written your own code to go through the nc files?

    Comment by AJ — December 13, 2011 @ 1:33 pm

    • Never mind… I see you’re way ahead of me… maybe I’ll copy your code instead🙂

      Comment by AJ — December 14, 2011 @ 1:40 pm


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