Tuesday, May 17, 2011

The Wager and Ocean Heat Content

Since I was playing with data to see if the 2015 climate wager a fair bet, I thought I may as well include the Ocean Heat Content (OHC) data. I linked to the data on Lucia's site were she was wading in on the tiff between Tisdale and Tamino.

The OHC data is probably some of the most important for determining the change in climate. It is also some of the worst data available. Tisdale honed in on some of the more resent data, from 2003, when the ARGO floats started measuring the temperature, salinity at depths of 2 kilometers. I have never played with this data before, but assumed that ARGO must have made some improvements. The ARGO data is far from perfect, but better than what came before.

In the chart above you can see that the OHC data is pretty noisy. Around 2001, there appears to be a flattening of the trend and less noise. The noise decreases from 2001 to about 2004, then stabilizes somewhat. The change in the noise is so much I can't even guess if there is the start of a real trend or if before 2001 the data was just pure crap. It is probably a little of both, but I don't think you can say with confidence anything but OHC has increased. I plotted the quarterly data in blue with annual in red.

Since I am playing with the wager, I took the same time frame, 2001 to present that I did with the other data. I stuffed a few short regression lines on the chart above, then made a new chart starting in 2011.

This shows there may be a real flattening trend, but that warming might increase until 2015. There are not enough data points in the quarterly data to do much predicting. The data looks odd though. I would expect seasonal fluctuations in the OHC, but not that much. Looking at the quarterly data the northern hemisphere winter has most of the peaks. That is not unexpected, the southern hemisphere has more ocean area. The angle of the sun though still favors the northern hemisphere. So I chopped out the first and second quarter data then made a new plot.

With a short time frame, noisy data and not many data points, this probably means nothing, but it is a little odd that here the possible trend turns negative. A negative trend that better matches the ENSO/PDO is what I would expect. With the limited data, comparing the first half of the year to the last half could show anything. Still that looks to be a fairly significant change in the slopes. Does it mean anything? Dunno. From a wager stand point, it reenforces my opinion that the wager is a toss up, but that is my gaming point of view not a very scientific point of view.

It does get me thinking though. Most scientists are looking for lags based on fix time periods. I think it is more reasonable that lags are likely related to threshold values. Fixed time lags, perfect correlations and dominate specific natural drivers are not what I would expect in a somewhat chaotic system. Natural variation can be amplified, but I doubt that a tight phased locked loop type of control is in charge of the amplification. A little extra CO2 or land use change or dry/wet annual change or touch of an increase/decrease in solar could shift the threshold. Throw in a few oscillation shifts and before long you have a complex puzzle.

When I was picking on Nicola, he was looking for lags that matched the small changes in solar energy and estimated about 60% natural forcing. That may be true in the past, even using the slightly outdated reconstructions, but it does not have to apply to the future. Wagering wisely requires knowing probabilities, but winning against players that also know the odds, requires the use of tells, hunches, patterns and gut instinct. You will never win every hand, but knowing your opponent tilts the odds in your favor, until he shifts his pattern.

UPDATE: After more eyeballing and even resorting to ttests, the data before the middle of 2003, sucks. It is not all that great after 2003 either. The ocean heat content has been dead flat since 2004 for all practical purposes. Mention the rise in OHC though and you may get better odds.

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