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Are we absolutely sure the oceans are warming faster than ever?

Foraminifera by Ernst Haeckel

Foraminifera by Ernst Haeckel

Ocean’s are the hottest they’ve ever been in the last 10,000 years!

Or so screamed the headlines, casting yet another death knell on humanity’s relationship with climate. Or so the media would hope! Afterall, the only thing making the planet warm in the last 10,000 years is mankind, right? It’s our annoying habit of burning up all the fossil fuels on the planet. And they’ve made the ocean the hottest in post ice-age history. Right? Right!

The headline began innocently enough – Rosenthal, et al., 2013, published an article in Science Magazine, the abstract and editor’s comment of which, are available at the Science Magazine website. In the abstract, the author’s comment that their findings indicate the following:

  1. (1) 6000-7000 years ago, during the middle of the Holocene Thermal Maximum, the ocean in the North Pacific  (by 2.1±0.4oC) and Antarctic Oceans (by 1.5±0.4oC), than during the past century,
  2. (2) During the Medieval Warming Period (950 -1250 A.D.), it was approximately 0.9oC warmer than during the last Little Ice Age (1550 and 1850 A.D.)
  3. (3) The warming in the middle of the 20th Century was approximately 0.65oC warmer than the last few centuries.

Well, a number of things jump out to me from that abstract:

  1. Without knowing what the ocean temperatures were during the Little Ice Age, the statements about the temperature of the water in the Medieval Warming period are almost rendered useless, and
  2. Hang on a minute here – but isn’t the IPCC now saying the ocean has been the reason why the temperatures have not risen as much as expected in the last 16 years or so as the ocean absorbed the otherwise warming that the models predicted? And yet, this article indicates that the ocean is cooler now than it has been during other times in the last 10,000 years and cooler than periods even within the last century?!
  3. How were they able to estimate the temperatures for the last 10,000 years when thermometers were only invented in the late 16th century?
Hyalinea balthica (after

Hyalinea balthica (after

Fortunately, the last question was the easiest to answer – ignoring the headlines of what is to follow, most media articles made it clear that the author’s of the paper had taken sediment core samples (i.e. drilled into the earth’s crust at 2 points in the ocean – and extracted a column of sediment. The sediment had been laid down in the ocean over an extended period of time, and as it gradually built up, the skeletal remains of a microscopic oceanic organism called Hyalinea balthica, were trapped in the sediment, gradually getting buried under successive layers of sediment over time. More about the environment Hyalinea balthica can be found here, as well as an abstract which gives you an idea these little organisms love warmer waters and have been favoured as paleoclimate indicators before.

But getting back to the media interpretation of the paper, there was certainly not much in the abstract to indicate there was more warming of the oceans now than there had been in the last 10,000 years – and indeed, even evidence to suggest the oceans had been warmer in the past.

However, not to be deterred, the media rushed out to tote headlines such as that at Time Science and Space: “Oceans Warming Faster Than They Have Over Past 10,000 Years” – published the same day as Rosenthal et al.’s article in the Science Magazine. Sadly, the evidence that Time is quoting must be from the article itself, because it bears no resemblance to the abstract available to the general public. Time indicated that the article said “middle depths have been warming some 15 times faster over the past 60 years than at any other time over the past 10,000 years” and “Over the last 60 years, however, water column temperatures increased by 0.32º F (.185º C)—roughly 15 times faster than any other time over the past 10,000 years.”

Hang on a minute – there was nothing in the abstract hinting the water column had warmed faster in the last 60 years – nothing! Furthermore, having nursemaided more than one drill rig in my lifetime (albeit, none on the bottom of the ocean floor), the top few feet (and usually a couple of meters) of any drill program are usually lost when drilling begins – how could the author’s know exactly what had happened in the last 60 years, as the last 60 years of sediment history was most likely about 10cm of sludge in their drill core recovery? I began to smell a hockeystick conspiracy where the last few decades of data were derived from sources other than what had made up the previous 10 centuries…

Alas, my library did not have a subscription to Science Magazine which was a shame as these quotes were certainly not implied in the abstract which to all intent purposes indicated the ocean was cooler in recent decades, not warmer – but then, I must focus on Time’s language ‘ the temperature has increased over the last 60 years by 0.185oC’ – it’s not really making the observation based on what the actual temperatures are today, but on how fast the rise in temperatures is.

The Guardian newspaper must also have been aware that the average person would not have access to the full article, and published a quote from the Rosenthal et al.’s paper that clarifies what is not mentioned in the abstract:

“…since about 1950, temperatures from just below the sea surface to ~1000 meter, increased by 0.18 degrees C. This seemingly small increase occurred an order of magnitude faster than suggested by the gradual change during the last 10,000 years thereby providing another indication for global warming.”

This was then put in context by the last sentence quoted from the Science Magazine paper;

But our results also show the temperature of the ocean interior is still much colder than at any time in the past 10,000 years thus, lagging the changes we see at the ocean surface.”

Ok… So one small part of the ocean off the coast of Indonesia (now) is warming faster than at any other time in the last 10,000 years – but it’s still cooler than we expect. A bit more in line with the abstract…

Elsewhere, the National Geographic didn’t want to be left out, and threw in a nice, largely unrelated discussion about sea level change as well. They also made Rosenthal sound ambivalent about the reported warming indicators from the paper.

Amazingly, I rummaged around a little more and found that blogger, Hockeyschtick, had not only provided a link to the article that the public could not readily get, but had provided quite a detailed analysis of the paper itself. The detailed analysis and copy of the original paper by Rosenthal et al. can be found at “New paper finds Pacific Ocean has been significantly warmer than the present throughout vast majority of past 10,000 years.”

With a name like “Hockeyschtick” one can imagine this blogger is one who was not impressed by thoroughly debunked ‘hockey stick’ graph that Al Gore used in “An Inconvenient Truth” to dramatically demonstrate the rise in temperatures due to fossil fuel consumption.

And, oh dear, according to Hockeyschtick even an interview with the author’s admit that at best, they have century scale resolution for the temperatures. There is no way they could – or should – be making claims that warming is occurring faster than at any other time in the last 10,000 years – to wit, from Rosenthal’s mouth himself (source: Watts up with that):

“The deep ocean tends to average and smooth the record … I think it’s fair to say that it’s unlikely that very rapid changes on the order of, let’s say, years or even decades … would show up in the record.”

Thank you, hockeyschtick – I just bookmarked you for insightful comment on climate science (seriously!).

And Rosenthal – are you being a little bit ambivalent in your comments, or as it would seem, trying to be cautious, but bullied into a corner to admit the warming in the last century is different and it’s mankind’s fault?! I wonder…

On a fascinating note, Michael Mann, clearly must have learnt something from the detailed analysis of his hockeystick graph and the scorn heaped upon the last 40 years or so when he switched to other methods to come up with the temperatures of the last century. Maybe because of this, and a strong desire to re-establish some of his science credentials after Climategate, he did actually point in the Huffington Post (in very fluffy language) that the tops of sediments cores are at best, poorly recovered. However, not to give me much faith in the man, he did then go onto to completely muddy the waters (he he) by throwing up lots of other papers that he thinks the author’s should have referred to before embarking on such a silly mission as analyzing core from the Indonesian seabed.


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