Ocean Temperatures: Is That Warming Statistically Significant?
The oceans as measured by ARGO are warming, but that warming is not only far less than the models predicted, it is far less even than the instrument error.
The background of a crucial point
Everyone agrees: 90% of the energy in the Earth’s climate system is stored in the oceans. Rocks and sand don’t transmit the heat down, except at incredibly slow rates. The wil-o’-the-wisp-atmosphere hardly holds any energy. But water covers 70% of the surface, to an average depth of 3,700m, and it can store septillions of joules.
Climate models say the Earth’s energy balance is out of whack, and therefore 90% of the extra energy trapped by increasing greenhouse gases is stored in the ocean. The oceans are warming (probably), but the extra energy found in the top 700m of the world’s oceans is not enough. The modelers argued the heat was hidden below, that from 700m-2,000m. Skeptics argue the missing energy was flung out to space. This is the big enchilada, and as far as measuring oceans goes, everything changed in 2003 when we finally got the ARGO system, and that’s why it’s worth a closer look now.
David points out that the errors might be seriously miscalculated. A single ARGO buoy (which measures ocean temperatures down to 2000m) has an uncertainty of about 0.1C. But using 3,000 buoys doesn’t make that uncertainty dramatically smaller when all that data is combined together. It would, if the 3,000 buoys were all measuring the same swimming pool. But each buoy measures a different piece of ocean, and the ocean does not have one global temperature. Or it would if all the world’s ocean localities warmed by the same increment due to global warming, in each time period. But that would be a very brave assumption, because different parts of the world’s oceans probably warm at different rates due to global warming. So the measurement uncertainty is closer to the instrument error of 0.1C than the 0.004C as claimed by fans of man-made global crisis, and since the oceans have only warmed by about 0.02C (if that) since we’ve been measuring it with ARGO, that tiny amount of warming might just be noise. Going back further, the pre-ARGO data is so bad that longer datasets have much larger uncertainties.
Overview of Measuring Ocean Temperatures
According to many neat diagonal graphs, the oceans are warming, it’s alarming, and we have to spend billions to stop it. But is that warming enough, and how accurately can we measure it anyway?
For some inexplicable reason NOAA publish graphs of ocean heat content (OHC) but not ocean temperatures — the later are what the equipment measures, and what we relate to. So we need to convert OHC back to degrees C to find out the change in temperature.
Inspired by Willis Eschenbach, David Evans has done it with the ARGO data. (David doesn’t use non-ARGO data because he considers the XBT and buckets-off-boats stuff to be whimsical fantasy with error bars up where the unicorns fly, see below.) ARGO data only properly started in 2003, and any data at-depth before then was sparse. Compare it to the detail in our atmospheric measurements. We’ve been releasing weather-balloons twice a day from 800 sitesaround the Earth for five decades. To measure the global oceans we used 50 ships “of opportunity” (which happened to be in a shipping-lane) and XBT’s were fired down, not twice a day but once every few weeks. And vast tracts of the ocean hardly got measured, ever, especially the deepest parts. (XBT’s only get down to about 800m.)
ARGO data is good, but short. It’s fair to ask if such a short span is meaningful? Since thou shalt not create nor destroy energy — it is fair. The imbalance caused by extra CO2 has run day in and day out for nearly 3000 days since ARGO began. That energy has to be somewhere.
Where are the error bars?
This is the standard diagonal scare-graph for ocean temperatures, but with added notes about which parts are reliable.
It looks like a convincingly big rise, but it’s not enough, and the error bars are huge. Even on the accurate ARGO buoys error margins are probably not a lot less than 0.1C. GRAPH UPDATED*
David Evans separated the layers of ocean so we can compare the rate of warming in the deeper layer, 700m – 2,000m, with that from the top layer, 0 – 700m. (Bear in mind, the “top” 700 m is not exactly shallow — it is the hull-crush depth of a military submarine.) David found that the rate of warming in the deeper layer is the same as the rate in the top 700m.
Over this short period, there is no acceleration evident in either layer.
If the instrument error is 0.1C, the error bars would be off the scale. [Jo says, “look” the error bars are marked in white…] GRAPH UPDATED*
You might almost think the slight appearance of warming matters, but let’s put it in perspective — it’s not remotely close to what the models predicted.
Though the funny thing about having wider error bars is that even though the results look so different from the models, the predictions could still fall within the error bars! Why haven’t the modelers announced it? [Prediction from Jo: Trenberth channels Santer 2008, “reconciles model and ARGO data by revisiting error estimations!” Coming soon, with 17 authors and a major press release… Researchers investigate errors and find the missing energy!].
Dr David Evans discusses the ocean data
These notes about the graphs above and the following explanation of how he got the graphs and why he chooses to use ARGO over the other data sets are thanks to David.
Climate models predict the top 700m is warming at 0.07C per decade
The climate models predict that ocean heat content is increasing at about 0.7 × 10^22 Joules per year. (See Hansen et al, 2005: where the increase in ocean heat content per square meter of surface, in the upper 750m, according to typical models, is around 6.0 Watt·year/m2 per year, which converts to 0.7 × 10^22 Joules per year for the entire ocean as explained at Bob Tisdale’s site. Converting to temperature, this corresponds to about 0.7 × 0.01C = 0.007 C per year.)
The deeper ocean
The deeper 700m – 2,000m layer has warmed at the same rate as the upper 0 – 700m layer in the deeper Argo period (measured from Q1 2005).
This contradicts a meme that the deeper oceans are warming faster. It is correct that the heat content of the deeper layer is rising faster, but when converted to temperature it turns out that both layers have warmed at the same rate. There is 1.85 2.18 times as much water in the deeper layer (700m – 2,000m) as the upper layer (0 – 700m).
The warming of the planet is allegedly because of a warmer atmosphere, due to more CO2. The extra warmth would therefore have to pass from the atmosphere through the 0 – 700m layer to reach the 700 – 2,000m layer of the ocean. Schemes whereby currents could somehow move the heat from the surface to below 700m without warming the first 700m on average have been proposed, and maybe some are plausible — but warmer water rises.
The upper layer 0 – 700m is much better measured by Argo than the deeper 700 – 2,000m layer, with both earlier and denser data. In any conflict between the 0 – 700m and 700 – 2,000m data, the former is far more likely to be correct.
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