via Eurekalert today…
The study emphasises that this trend came to an end with the beginning of the Industrial Revolution and the resulting global warming caused by human activity.
From the UNIVERSITAT AUTONOMA DE BARCELONA
The Industrial Revolution put an end to 1,800 years of ocean cooling
The high frequency and magnitude of volcanic eruptions could have been the cause of the progressive cooling of ocean surfaces over a period of 1,800 years. This is made apparent in an international study published recently in the journal Nature Geoscience, involving researcher P. Graham Mortyn of the Institute for Environmental Science and Technology (ICTA-UAB) and the UAB Department of Geography.
The study emphasises that this trend came to an end with the beginning of the Industrial Revolution and the resulting global warming caused by human activity. It further shows that the lowest temperatures in the first 1,800 years of the Common Era were recorded between the 16th and the 18th centuries, a period known as the “Little Ice Age”.
Earlier research had already shown that volcanic explosions cause the atmosphere to cool. The present study demonstrates that the oceans can absorb and capture more heat than the atmosphere over longer periods of time, thus attenuating global temperature changes in the short term. These alterations in temperature can be prolonged when the volcanic eruptions are concentrated into a short space of time.
These findings bring a new perspective to the study of regional and global variations in ocean-surface temperature over the centuries, before the appearance of anthropogenic (human activity-induced) climate change.
The researchers combined, for the first time, 57 previous works on sea-surface temperature changes, which are calculated from fossil remains extracted from oceans all over the world, from the Poles to the Tropics. The results were compared with data from terrestrial indicators, such as tree rings or ice cores. These revealed a similar cooling trend.
To investigate the causes of this cooling – more robust between the years 800 and 1800 – they used climate models and they examined how the ocean surface reacted to factors like solar activity, changes in the Earth’s orbital patterns, land use, greenhouse gases and volcanic activity. The last of these proved to be of importance. In order to analyse long-term trends, the team grouped the data into periods of 200 years.
P. Graham Mortyn is a member of the Ocean2k group within PAGES (Past Global Changes), which has over 75 members connected to a network of close on 600 highly-experienced scientists. Mortyn lays emphasis on how this group worked with data from previous publications available to the public and archived databases that meet extremely strict criteria, and how they made regular use of Skype conferencing, shared Google documents and other innovative technological resources.
The researchers point out that understanding how these factors caused changes in ocean temperature in the past could give us an insight into future changes in climate.
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As is typical with shonky alarmist press releases in climate science these days, they don’t bother to name the study or present a DOI. So I looked it up. Laughably, there’s that favorite climate buzzword again, “robust”. It turns out this was published on August 17th, and P. Graham Mortyn is the 7th from the top named author. Given that and the lateness of the press release, this looks like a ploy for attention. And the press release reads quite a bit more alarmist than the abstract, which does not mention the industrial revolution.
Robust global ocean cooling trend for the pre-industrial Common Era
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, Kaustubh Thirumalai, Helena L. Filipsson & Vasile Ersek
Nature Geoscience 8, 671–677 (2015) doi:10.1038/ngeo2510 Received 24 October 2014 Accepted 17 July 2015 Published online 17 August 2015
Abstract
The oceans mediate the response of global climate to natural and anthropogenic forcings. Yet for the past 2,000 years — a key interval for understanding the present and future climate response to these forcings — global sea surface temperature changes and the underlying driving mechanisms are poorly constrained. Here we present a global synthesis of sea surface temperatures for the Common Era (CE) derived from 57 individual marine reconstructions that meet strict quality control criteria. We observe a cooling trend from 1 to 1800 CE that is robust against explicit tests for potential biases in the reconstructions. Between 801 and 1800 CE, the surface cooling trend is qualitatively consistent with an independent synthesis of terrestrial temperature reconstructions, and with a sea surface temperature composite derived from an ensemble of climate model simulations using best estimates of past external radiative forcings. Climate simulations using single and cumulative forcings suggest that the ocean surface cooling trend from 801 to 1800 CE is not primarily a response to orbital forcing but arises from a high frequency of explosive volcanism. Our results show that repeated clusters of volcanic eruptions can induce a net negative radiative forcing that results in a centennial and global scale cooling trend via a decline in mixed-layer oceanic heat content.
UPDATE: Steve McIntyre looks at the oceans2K data, and surmises it’s a bit hyped up. (h/t CTM)
The long-awaited (and long overdue) PAGES2K synthesis of 57 high-resolution ocean sediment series (OCEAN2K) was published a couple of weeks ago (see here here). Co-author Michael Evans’ announcement made the results sound like the latest and perhaps most dramatic Hockey Stick yet:
Today, the Earth is warming about 20 times faster than it cooled during the past 1,800 years,” said Michael Evans, second author of the study and an associate professor in the University of Maryland’s Department of Geology and Earth System Science Interdisciplinary Center (ESSIC). “This study truly highlights the profound effects we are having on our climate today.”
A couple of news outlets announced its release with headlines like “1,800 years of global ocean cooling halted by global warming”, but the the event passed unnoticed at realclimate and the newest “Hockey Stick” was somehow omitted from David Appell’s list of bladed objects.
The OCEAN2K Reconstruction
One of the reasons for the strange lack of interest in this newest proxy “Hockey Stick” was that the proxy data didn’t actually show “the climate was warming about 20 times faster than it cooled during the past 1,800 years”. The OCEAN2K reconstruction (see Figure 1 below) had a shape that even David Appell would be hard-pressed to describe as a “Hockey Stick”. It showed a small decrease over the past two millennia with the most recent value having a tiny uptick from its predecessor, but, whatever image one might choose to describe its shape, “Hockey Stick” is not one of them.
FAQ Figure 1: Results of the global sea surface temperature compilation from Ocean2k: A cooling over the past two millenium was reversed only in the most recent two centuries. Fifty-seven previously published and publicly available marine sea surface temperature reconstructions were combined and compiled into 200-year brackets, represented by the boxes. The thin horizontal lines dividing each box are the median of the values in that box. The thick blue line is the median of these values weighted for differences in the region of the global ocean in which they were found. (More in Figure 2a in the paper and Supplementary Table S13. ) Link
Read it all here: http://climateaudit.org/2015/09/04/the-ocean2k-hockey-stick/#more-21349
Better keep those guys well clear of calderas.
volcanic eruptions “could”- binned.
So what was the temperature before the volcanic cooling?
Any explanation at all is touted loudly except the actual one, which doesn’t support the ideological agenda.
Ha. They fart in our general direction.*
57 —. Heinze —>.Beans —> Gas
* Carefully** recycled from the original Monty Python.
** Well as careful as “climate scientists” are.
I made a point here some years ago that I felt that it was at least as likely that the rise in temperature actually caused the Industrial Revolution. Someone wrote an eloquent reply agreeing with me.
The cognitive dissonance is unveiling the ignorance.
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Does this mean we have to start worrying about the Next Ice Age again?
Reading between the lines of the actual abstract, a better way to restate their conclusions might be this:
Sadly, if the authors had actually read e.g.
http://ftp.pages-igbp.org/download/docs/books/Paleoclimate_global_change_and_the_future/d-chapter2.pdf
in particular the section near the end concerning atmospheric aerosols, they would have realized that we have direct evidence of aerosol concentrations due to e.g. vulcanism over the last 1000 years and they are flat.
Oops. Oh, and not only are they flat, they sharply go up starting in roughly 1900 from a baseline of roughly 50 ppm to peak well over 150 ppm. That is, they are somewhere between two and three times their value across the interval they claim was cooled by excess vulcanism. NO_2 is also nearly flat, although for technical reasons it is a spottier record and it starts going up almost parallel with CO_2 in roughly 1800.
Finally, they missed the recent paper that recomputed the probable climate sensitivity to aerosols that concluded that aerosols have almost no effect on climate. Climate models in general have overestimated the cooling effect of aerosols because they only have two knobs on any relevant time scale within the late Holocene. GHGs warm, aerosols cool. In order to make this so, they had to make aerosols a major cooling factor in order to reproduce the temperature decreasing-to-doldrums observed in the 1940 to 1975 stretch, because CO2 was steadily increasing across that interval but the temperature was not! Fortunately, pollution controls instituted in the 1970s started to decrease aerosols, which apparently kicked off superfast warming by the mid-80’s in this two-knob model of the climate. It wasn’t until the doldrums returned after only 15 years around 2000 that it became increasingly clear that high matched sensitivity to CO2 and aerosols (in opposite directions) just wouldn’t fly, because again CO2 marched up, faster than before, and temperature has peskily refused to cooperate in spite of a general and continuing reduction in aerosols, both man-made and volcanic. This is pretty direct evidence that there is a lot more going on than two-knob models are capable of resolving.
Current estimates of aerosol cooling indicate that it was overestimated by as much as a factor of three in the GCMs in CMIP5. In order to reproduce the temperature increase across the reference period (which happened to be the one stretch of strong warming visible in the last 75 years!) by means of cancellation of opposing terms, they had to overestimate climate sensitivity, by about the same amount. Again, there is no real question about this — we have very good data on aerosols over the last century, and we have the direct observations of the variation of atmospheric transparency at Mauna Loa as well, which show that even major (VEI 5 and up) volcanic events have almost no effect on top of troposphere insolation and what little they have is confined to 1 to 3 years after the cessation of eruption and is often hemispheric and not global. The temperature record is poorly correlated with volcanic activity, where again major eruptions can have a small effect (comparable to the rate of natural fluctuation and hence almost indistinguishable from it) for a couple or three years (which is also comparable to the timescale of natural fluctuation and hence is almost indistinguishable from it). The indistinguishability is easily proven by playing Willis’ game “Hunt the volcano” — trying to guess when major eruptions occurred by looking at the global temperature anomaly without any date scale and within panels of time that are deliberately scrambled. IMO it is impossible to beat random chance, but play for yourself if you doubt me.
So this would be a great paper if its primary conclusion were not already disproven by the copious data already available! Which makes it a less than great paper, and an even worse press release.
Accepting that the paper does demonstrate a general slow cooling of the oceans over 1000 years or so, it fails to explain either the MWP or the LIA, both (now) generally accepted as being true global events. The latter in particular cannot be explained by vulcanism, as a glance at sulphates as a function of time in Greenland ice cores would demostrate, if they bothered to look. It is also the case that land temperatures can countervary or move independently of SSTs, as SSTs have been remarkably flat outside of jumps associated with ENSO events while the global anomalies have more or less continuously increased.
What all of this suggests — to me — is that global climate models are pitifully inadequate to explain the past climate record. There are more than two knobs, and it isn’t clear that they even have the sign of the feedbacks and direct effects right in all cases. There are almost certainly missing knobs. Finally, some of those missing knobs are very likely to be linked to pure chaos and self-oscillation — the spontaneous appearance of dissipative oscillators in a nonlinear driven open system. Given a number of these oscillators operating at the same time, there are bound to be periods where they heterodyne and others when they cancel each other out, periods of multiple decades to centuries. Since there is little reason to think that the modes themselves are stable or even persistent on century to millennium time scales, the quasi-periods of these oscillations can abruptly shift. IMO this is by far the best explanation for e.g. D-O or Heinrich events, and even explains why they are not strictly periodic but subject to abrupt changes in period or phase or disappearing altogether for a few cycles.
Note well that this doesn’t rule out still other missing physics. One interesting feature of self-oscillation is that it is often “greedy” (or sensitive to signals on its input) and will tend to slave to and amplify even small fourier variations in their input if they are close to the natural frequencies they are prone to self-generate for physical reasons. If you like, they can be subject to selective “resonance” and amplify signals that are by themselves too small to take seriously into comparatively large variation in state. Transistors and tubes and photodiodes are good examples of this being set up deliberately (and are easy to turn into oscillators and with even a little feedback, often do). The Earth has a huge energy budget flowing through it on a daily basis, on average taking almost all of a TOA insolation that varies from 1325 or so watts/m^2 up to 1415 watts/m^2 as the Earth orbits the sun and reflecting, absorbing, and reradiating it away to outer space. It has obvious strong fourier signals superimposed on this forcing, and has a complex surface structure of sinks and sources. The energy transport that results is rich with self-oscillation, from winds that blow, then pause, then blow, then pause, to waves peak every seventh wave as they march towards the shore, to spectrum of slow and fast gyrations in thermohaline oceanic transport, to the named atmospheric multidecadal oscillations.
Climate models can accurately capture almost none of this. What they never seem to show, in these papers that assert that “climate models prove this or that” is that the actual output of most climate models is a wide bundle of completely disparate “future possible climates” produced from a tiny spread in initial conditions or parameter values, which in any event are not precisely knowable, let alone known. These future climates are then averaged, and it is this average that is supposedly a valid predictor or hindcaster of our actual climate. But it isn’t! There is no mathematical or empirical support for this implicit assertion. The average of many chaotic trajectories produced by a chaotic system is not a chaotic trajectory and will in all probability not correctly represent self-oscillation modes that dominate actual true trajectories.
That is, a given GCM might — with luck — spontaneously produce one or more multidecadal oscillations. They probably will not correspond in frequency or amplitude or location to the actual PDO, ENSO, AMO, AO, NAO, monsoon, etc, but there will be something. Any realistic climate will have features like these. But the average of many climates with features like these will not have these required features! And the features matter, because they are directly related to the nonlinear efficiency of energy transport and hence to the non-stationary “equilibrium” temperatures maintained in the open system. As is often noted, even a small shift in oceanic or atmospheric circulation patterns can dramatically affect energy dissipation or retention in the system and result in warming or cooling much greater than the supposed and miscomputed effect of GHG/aerosol forcing within the system. By averaging this away, one arrives at a “climate trajectory” that is truly meaningless, doubly so given the many other absurdities in the GCMs associated with the mismatched spatiotemporal scales of the dynamics, the non-uniformity of the grid usually used, and the lack of knowledge of the physics and forcings that is made up of many assumptions that frankly cannot be proven or even meaningfully tested.
The final conclusion can only be that politics once again has intruded on science. The paper could have left off all of its assertions of cause based on GCMs and presented only the data, and it would have been good observational science. To present at the same time a study that contradicts the actual data on vulcanism and hence is probably wrong before it is even in print, and then to throw in some good old alarmism right before a major meeting intended to spend a substantial fraction of the world’s income, disposible or not, for the indefinite future and to the definite enrichment of many of the most “interested” parties, including conclusions absent even from the paper itself but safely insulated from scientic criticism, in the public arena, is one more example of Science, Done Wrong.
It is just sad.
rgb
Excellent.
Also the location of volcanoes affects their effect on the atmosphere. In general however, even when there is cooling, it’s usually short term, ie years at most. The longer term effect is generally warming.
There is so much wrong with this paper that it’s hard to know where to start.
Nice. The paper now reminds me of the scientists that have been predicting increasing trends in extreme weather due to climate change, evidently without realizing that NOAA keeps very good records of those hurricanes and tornadoes they keep on predicting, and they don’t show an increasing trend.
I am late in replying, but thanks for this nuanced analysis.
For those wondering if your “two knob” take is correct… I’ve been looking at, and thinking about, models and simulations for a while. I had already noticed that Hansen seemed to think the only significant influences on global temperature are stratospheric aerosols and atmospheric trace gases, that is GHGs, as far back as 1988 (or as recently as 1988, depending on one’s frame of reference).
http://pubs.giss.nasa.gov/abs/ha02700w.html
If he added any other knobs in his follow-up 1998 paper, I can’t tell. ISTM that he was mostly interested in exercising his confirmation bias here.
http://pubs.giss.nasa.gov/abs/ha01100t.html
Sorry, I meant “they are flat over the interval from 1000 to 1900 CE” relevant to the assertion that they caused the cooling from 800 to 1800 asserted in the paper.
rgb
Looking at the graph the rate of warming looks pretty regular and steady since 1700 to 1900 to me.
A few points.
1 How was there enough extra man released Co2 in the atmosphere to have any effect back then.
2, Why is the warming rate pretty much the same since 1700
3 Could this just be a small natural rebound from the little ice age cooling?
4 If this is CO2 driven ocean warming, would it not kick in later when the increase from 280 ppm was greater. Was it even enough in 1900 to have much influence at all?
Looks more like an argument for natural variation in temperature to me.
No article you are wrong and what I have wrote below is correct and applies to the last 7000 years or so and the last 1800 years.
If one goes back to the Holocene Optimum the question is how fast is the earth cooling?
Since the Holocene Optimum 8000 years ago the earth has been in a gradual overall cooling trend which has continued up to today punctuated by spikes of warmth such as the Roman ,Medieval and Modern warm periods.
The main drives of this are Milankovitch Cycles which were more favorable for warmer conditions 8000 years ago in contrast to today , with prolonged periods of active and minimum solar activity superimposed upon this slow gradual cooling trend giving the spikes of warmth I referred to in the above and also periods of cold such as the Little Ice Age.
Further refinement to the climate coming from ENSO, volcanic activity , the phase of the PDO/AMO but these are temporary earth intrinsic climatic factors superimposed upon the general broader climatic trend.
All the warming the article refers to which has happened since the end of the Little Ice Age, is just a spike of relative warmth within the still overall cooling trend due to the big pick up in solar activity from the period 1840-2005 versus the period 1275-1840.
Post 2005 solar activity has returned to minimum conditions and I suspect the overall cooling global temperature trend which as been in progress for the past 8000 years ago will exert itself once again.
We will be finding this out in the near future due to the prolonged minimum solar activity that is now in progress post 2005
Something I mentioned over at Climate Audit, which was promptly and appropriately squelched by Steve, is that we had better hope that the uptick of ocean temperature is predominantly caused by nature, for if man is responsible, we have chosen a feeble and inadequate method to sustain the trend. Only if nature has bounced us off the dire coldth do we have much hope of longer avoiding the chilling cliff at the end of the Holocene. The Little Ice Age was the coldest depths of the Holocene, and we are at half precession.
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But I’ll take any little effort which wisps the Coldisch Moth away from its Great Glacial Attractor.
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Great. It was warmer 2000 years ago and mankind did not die. History tells that Roman age was quite prosperous.
Pity that it is difficult to refer figure 1 on the original source without showing the political speculation. Just the picture is quite pale. I would like to use original source in local discussion forums.
The rapid 3~5 year warming recovery following large volcanic events conclusively shows that atmospheric temps are very insensitive, which blows the CAGW hypothesis to pieces as it assumes hypersensitivity involving runaway feedback loops from very tiny changes in IR flux.
The CAGW alarmists are desperately hoping for a large volcanic event, which they can blame for almost 20 years of flat global temperature trends; i.e. “Our models worked perfectly but those cursed volcanos screwed everything up.”….
Not so much..
The paper is a waste of money.
Those have to be the widest error bars I’ve ever seen in a published paper.
Well, still it’s important to publish papers that fail the Null Hypothesis test. There’s too much bias in favor of high confidence papers in general. Note the trouble the medical world and psychology world got into with this.
Peter.
Even if their climate models are correct shouldn’t we be grateful? Today we are living longer, healthier with more food than ever before. Cold is not necessarily better……these folks have warm phobia.
I wish they’d stop playing the ridiculous “volcano card”. They’re a bunch of Jokers.
http://climate.envsci.rutgers.edu/pdf/ROG2000.pdf
This study has it about right as far as the volcano/climate connection.
The oceans mediate the response of global climate to natural and anthropogenic forcings.
The usual atmosphere-centric BS. Oceans do not “mediate”, they drive climate fluctuations which are always happening naturally. The 97 percent value that folks are so fond of actually applies to the climate heat budget – 97% in the ocean, 3% in the atmosphere. All that ocean heat is not passive and static but agitated in chaotic-nonlinear mixing processes. Thus the circulating global oceans serve up continuous climate change.
It is wrong to imagine that climate is driven by the 3% and not the 97%, i.e. by the atmosphere by processes like volcanoes and anthropogenic emissions. Volcanoes are a fart in a thunderstorm – posts by Willis and others have shown how grossly exaggerated the supposed climate effect of volcanoes are. Stories about a “year without a summer” don’t stand up to scrutiny. Their effects are minor and short-lived unless they reach the scale of supervolcanoes or a flood basalt.
The ocean does not “mediate” climate, it drives it, the atmosphere mediates ocean oscillations.
And finally, please stop using that “F” word in regard to climate. It is not forced from outside, it forces itself by its own internal dynamic (although there can be weak periodic forcing from astrophysical cycles.)
Looks like the folks in Barcelona didn’t get Mike Mann’s memo saying there was no Little Ice Age.