Conspiracies, volcanoes, and two thousand years of ocean cooling and warming

Deniers at WUWT are (belatedly) trying to shoot down a paper published in Nature GeoScience last month. It's from authors who are part of the Ocean2k project, the ocean component of the PAGES 2K international consortium. The lead author is Helen McGregor from the University of Wollongong in Australia.

Anthony Watts was first to protest (archived here). In a bout of denial at WUWT, he claimed that just because there were a lot of volcanic eruptions on earth from somewhere around 1200 AD to 1800 AD, it doesn't mean they caused the observed cooling. He wrote a headline: "The new poster child for ‘correlation is not causation’: industrial revolution ended 1800 years of volcanic induced cooling".

In that one headline he rejected both greenhouse and volcanic forcing. Naturally, he didn't say what he thinks caused the earth to cool over time, or what is causing the current warming. More of the WUWT magic?


Anthony's protest was weak. It consisted mainly of his headline, and a complaint that there was another press release about it recently. He didn't notice or know about the press release when the paper was first published. He later added an update that denier blogger Steve McIntyre was writing about it, though Anthony didn't understand what Steve was writing. (And I doubt that Steve McIntyre understood what he was writing either going by his past performance.) Anthony can't even get denier articles right. Compare what Anthony said: "Steve McIntyre looks at the oceans2K data, and surmises it’s a bit hyped up." with what Steve McIntyre wrote, which was the opposite: "One of the reasons for the strange lack of interest..."

At WUWT today it's the turn of Willis Eschenbach (archived here).  It's fairly obvious that Willis didn't read the paper, or if he did he didn't understand it. He didn't seem to understand much at all about it. He posted part of Figure 2 from the paper and wrote:

It shows the data in 200-year bins, centered in the middle of each bin, so the first bin is from 0-200 AD and the last bin is from 1800-2000 AD. I saw that graph and I said “Huh?” The change from 1700 to 1900 is not anywhere near 20 times as steep as the drop from the start of the study to the present, as Michael Evans claims. That is simply not true.

Yet Willis didn't provide any evidence to show whether it was true or not.

Two thousand years of sea surface cooling

Below is the top part of Figure 2 from the paper. I've added the caption from the paper. The bin on the left is from 1 CE to 200 CE. The bin on the right is from 1801 to 2000. Click the image to enlarge it.

Figure 2 | Ocean2k global SST composite and sensitivity analyses. a, Standardized Ocean2k SST synthesis. Lines are the N = 57 reconstructions, coloured by ocean basin (see b). Box plots show 25th to 75th percentile range (black box), median (black horizontal lines) and outliers (red crosses) to approximately 99.3% of the data range (black dashed lines and caps (‘whiskers’)) assuming normally distributed bin contents (Methods). Thick black line is the median of the ocean basin area-weighted composite (Supplement section 5). 

You can see from the above the distinct cooling trend from around 801 CE onwards, and particularly from around 1200 CE till recently. Some further explanation of the work is important.

The paper is the report of an effort by 15 researchers to analyse 57 different sea surface temperature reconstructions so as to develop a global reconstruction of sea surface temperature anomalies going back 2000 years. They put the data from these 57 separate reconstructions into 200 year bins, which allowed them to see long term trends by basin and overall. (This wasn't a simple task. The researchers had to make sure they were comparing like with like. The paper and supplementary information describes how they did this.) They also compared the result to land-based reconstructions, and found similar patterns.

What they found is shown in Figure 2 above. That there was a distinct cooling from around a thousand years ago to around 1800.

The researchers didn't leave it at that though. They went further to investigate what caused the observed cooling trend. It turned out to be what has been suggested in other papers - volcanic eruptions. From the press release at ScienceDaily.com:

To investigate the cause of the cooling trend, the researchers turned to climate models. They examined how sea-surface temperatures reacted to various "forcing" factors, such as changes in solar output, Earth's orbit, land use, volcanic activity and greenhouse gases. Only volcanic events resulted in a cooling trend that matched the team's real-world observations.

What about recent warming?

The paper itself was focused on paleo records from proxy indicators of sea surface temperature for the pre-industrial era. What has happened in the instrumental era? Well, there are modern reconstructions based on instrumental records. Here is what's happened to sea surface temperature since 1850, from the UK Met Office HadSST record.

Data source: UK Met Office Hadley Centre

I've plotted it as an anomaly from the 1851 to 1880 period. Does Willis Eschenbach not know that sea surface temperatures have been going through the roof? I've noticed that Willis doesn't talk about or plot surface temperatures on land or sea very often. He can't face the fact that he's wrong when he claims that temperatures only fluctuated "±0.3°C over the 20th century". They didn't. Temperatures have been going up and up, not up and down.

Putting it together with recent warming

This paper was presented as a progress report so I take that to mean this is a work in progress. It contains all sorts of caveats as well as some clear messages. If you compare the current sea surface warming with that of the past 2,000 years, it's pretty obvious that things have turned around. Particularly the cooling of the Little Ice Age years. From the press release, one of the authors says how they attributed the cooling to volcanic forcing (my emphasis):

"No matter how we divided the data set, the cooling trend stands out as a robust signal," McGregor said.

To investigate the cause of the cooling trend, the researchers turned to climate models. They examined how sea-surface temperatures reacted to various "forcing" factors, such as changes in solar output, Earth's orbit, land use, volcanic activity and greenhouse gases. Only volcanic events resulted in a cooling trend that matched the team's real-world observations.

Sea surface temperatures have risen by around 1°C in a little more than one hundred years. That's a very fast increase - as expected with the rise in greenhouse gases. In the press release, one of the authors, Michael Evans is quoted as saying:

Today, the Earth is warming about 20 times faster than it cooled during the past 1,800 years.

Willis Eschenbach's ineptitude

Willis doesn't believe him that it's warming so much faster today. But he doesn't provide any evidence to the contrary. He might think he has, but he's wrong. Willis put up a bunch of charts claiming they were "individual records". Unlike the researchers, Willis didn't bother to try to analyse any of the records he showed. He certainly made no effort to align them with one another so they could be compared. He didn't bother commenting on where the records were, or whether they were in upwelling regions (as the researchers did). Willis didn't discuss what the researchers did. I doubt he knew. He did get all hoity toity and seemed to be operating under a fantasy that any serious scientist would take notice of a science denier, and wrote:

I cannot object in strong enough terms to professionals passing this nonsense off as science. They’ve included several short segments that show the Pacific warming very rapidly, along with another short segment showing it warming and then cooling, and a final short segment that shows it not changing at all since the year 1300… how can anyone mistake this foolishness for actual scientific findings?

All that shows is that Willis doesn't know how to interpret data. Remember, this is the same Willis who can't tell the difference between a feedback and a forcing, and who thinks he was the first to discover tropical thunderstorms!

Challenges of a global sea surface temperature reconstruction

If Willis had made some time to read the paper he might have taken notice of this caution:

The temporal diversity and spatial distribution of the 57 reconstructions present methodological challenges for generating a global synthesis product.

Then the authors proceeded to describe how they met those challenges. Hint for Willis: You can't assume that any individual reconstruction can be used as a stand-alone representation of temperature of the surface of any entire ocean basin.  To illustrate this point, the paper includes a map showing the location of the different reconstructions (white dots), with a number where there is more than one reconstruction. (Click to enlarge.)

Figure 1 | Correlation map and locations of the 57 reconstructions in the Ocean2k SST synthesis. Map is based on six climate model simulations for the interval 801–1800 ce (Supplementary Table S4). For each simulation, SST data were composited into 200-yr bins, and the correlation between grid point SST and model global average SST was calculated (Supplementary Section 5). The map shows the six-model median correlation coefficient (colours). Numbers indicate where multiple SST reconstructions are from nearby locations. The correlation map qualitatively suggests that mean SST at the 57 locations is representative of global mean SST on centennial timescales.

As the caption states, the above map is based on climate model simulations. The locations of the 57 reconstructions are shown as white dots. The list of 57 reconstructions is provided in Table S1 in the supplementary information (pp 6-10). It's only when the data are analysed and combined in the manner that the Ocean2k team did that you can get an indication of global changes over time. Willis Eschenbach is blowing smoke - and as usual, doesn't know what he's doing.

Steve McIntyre's conspiracy theory

Steve McIntyre wrote about the paper too.  Steve has apparently taken time off from inflating footballs to read a bit of science. Along the way he indulged in some conspiracy ideation, writing:

Had the results been more HS-like, it’s hard to believe that the OCEAN2K authors would not have found a way of publishing them in time for AR5.  It seems to me that, since the results were “bad”, the authors seem to have felt little urgency.

His "HS" stands for hockey stick. And he thinks the results were bad? He doesn't explain why he thinks that, except that he couldn't find his hockey stick. That's because he was looking in the wrong place. Apparently Steve isn't aware of the fact that there is a modern instrumental record. He didn't read how the paper was about proxy reconstructions, focusing on pre-industrial times. Which is odd, since it was in the title.

The youngest bin aggregates data from 1801 to 2000. Thus it arguably goes from the coldest period of the past 2000 years to the hottest period, with the coldest years being around 100 years ago, and the last three decades or so of last century showing dramatic warming (see chart above).  And it doesn't include data from this century. In other words, that most recent bin is dominated by colder temperatures, not the recent hottest temperatures. If deniers were to tack the modern sea surface temperature record (as shown in the chart above) onto the paleo data, then they'd find their hockey stick. (Steve has as big a blind spot as Willis and other deniers when it comes to observations taken by modern instruments. He ignores them.)

From the WUWT comments

This is a mixed bag. As usual, I've linked to each comment. A lot of deniers seem to confuse the science around the medieval climate anomaly and the Little Ice Age. That's what comes of reading pseudo-science instead of science.

Rob Morrow thinks there was no Little Ice Age and wrote:

September 9, 2015 at 11:37 am
Clearly Mann’s graph didn’t go far enough, temperature wasn’t flat it was cooling! If the paper wasn’t paywalled it would be worth reading for a laugh.

Bryan A also thinks that there wasn't a Little Ice Age:

September 9, 2015 at 12:45 pm
But the more they cool the past to “Prove” there isn’t really a Hiatus in warming the further the likelihood that the LIA will need to exist as more than a regional effect Or will they then Re-warm everywhere 

Poor whiten has got all befuddled with all the different conflicting denier memes. That's what comes from sticking to climate conspiracy blogs. He or she doesn't know what to think and is definitely missing more than something.

September 9, 2015 at 11:54 am
Maybe I am missing something here, gone too quickly through this one,,,,,,but is basically the claim in this one that the industrial revolution started before LIA ended?!
Did actually the industrial revolution started by 1660?!
Are this guys claiming that their models are better than GCMs, when GCMs actually somehow show that there is no any global warming due to CO2 emissions either natural or human prior to 1960?
Can some one be kind enough to explain the actual point of this study, if I have got it wrong in principle?!
thanks in advance.
cheers

Bryan A almost has a breakthrough. The light switch is there within his reach but he can't quite make himself flip it.

September 9, 2015 at 12:57 pm
What I read in it was that the “Cooling” (into the LIA) was presumably caused by Volcanism over an 1800 year period while the Warming (assumed from Industrial CO2) of the last 200 years is a driving factor of industry CO2 production.
The Problem I see is that the level of Industrial CO2 production back in 1700 is so miniscule when compared with today that it shouldn’t have a greater effect on temperature than the current levels of CO2 production has

Keep going Bryan A. You're almost there. What happened at the end of the Little Ice Age? The volcanic forcing abated. What happened during last century? A huge increase in atmospheric greenhouse gases. And they are still increasing. That's why the sea surface has been getting so hot lately.


Nick Stokes makes a valiant effort to inject some reason at WUWT.

September 9, 2015 at 12:24 pm
As they say, the data are binned, in 200 yr lots. “1900” means anything from 1800-2000, and so does include some modern warming.
But the resolution is far too low to look for anything reliable about the last few decades. This is a proxy based paper about the cooling stage. Information about the modern warming stage should be instrument based.

References and further reading 

Helen V. McGregor, Michael N. Evans, Hugues Goosse, Guillaume Leduc, Belen Martrat, Jason A. Addison, P. Graham Mortyn, Delia W. Oppo, Marit-Solveig Seidenkrantz, Marie-Alexandrine Sicre, Steven J. Phipps, Kandasamy Selvaraj, Kandasamy Thirumalai, Helena L. Filipsson, Vasile Ersek. "Robust global ocean cooling trend for the pre-industrial Common Era." Nature Geoscience, 2015; DOI: 10.1038/ngeo2510 (pdf here)

• FAQ here on the PAGES 2K website (h/t Ceist in the comments)
• 1,800 years of global ocean cooling halted by global warming - press release from ScienceDaily.com
• The Industrial Revolution put an end to 1,800 years of ocean cooling - press release from EurekAlert

Crowley, Thomas J., G. Zielinski, B. Vinther, R. Udisti, K. Kreutz, J. Cole-Dai, and E. Castellano. "Volcanism and the little ice age." PAGES news 16, no. 2 (2008): 22-23. (pdf here)

Gifford H Miller, John R. Southon, Chance Anderson, Helgi Björnsson, Thorvaldur Thordarson, Aslaug Geirsdottir, Yafang Zhong, Darren J Larsen, Bette L Otto-Bliesner, Marika M Holland, David Anthony Bailey, Kurt A. Refsnider, Scott J. Lehman. "Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks." Geophysical Research Letters, 2012; DOI: 10.1029/2011GL050168 (pdf here)


From the HotWhopper archives

• Willis Eschenbach makes false claims about surface temperature (again) - August 2015
• On forcing and feedback with Willis Eschenbach - August 2015
• Steve McIntyre's big blooper - mistaking water mass movement for water temperature! - April 2015
• Wondering Willis Eschenbach's Thunderstorm at WUWT - October 2013