News Brief by Kip Hansen — 30 November 2019
A recent study in Oceanography, the Official Magazine of The Oceanography Society, titled “Atlantic warming since the Little Ice Age” [.pdf here], is interesting in its entirety, with an Abstract as follows:
“Radiocarbon observations suggest that the deep Atlantic Ocean takes up to several centuries to fully respond to changes at the sea surface. Thus, the ocean’s memory is longer than the modern instrumental period of oceanography, and the determination of modern warming of the subsurface Atlantic requires information from paleoceanographic data sets. In particular, paleoceanographic proxy data compiled by the Ocean2k project indicate that there was a global cooling from the Medieval Warm Period to the Little Ice Age over the years 900−1800, followed by modern warming that began around 1850. An ocean simulation that is forced by a combined instrumental-proxy reconstruction of surface temperatures over the last 2,000 years shows that the deep Atlantic continues to cool even after the surface starts warming. As a consequence of the multicentury surface climate history, the ocean simulation suggests that the deep Atlantic doesn’t take up as much heat during the modern warming era as the case where the ocean was in equilibrium at 1750. Both historical hydrographic observations and proxy records of the subsurface Atlantic are needed to determine whether the effects of the Little Ice Age did indeed persist well after the surface climate had already shifted to warmer conditions.”
Those interested in the relationships between deep Atlantic Ocean water temperature, surface Atlantic water temperature, and possible effect on climate — and, of course, effects of atmospheric climate on deep Atlantic Ocean temperature and the ocean’s heat uptake and release — should read the whole paper.
Of particular interest for today’s Climate Debate are these three graphs — the first two of which are simply copied from the paper itself, including their captions:
This first graph shows the Ocean2K reconstruction of global surface temperatures (anomaly with baseline 15 CE — broad black trace) and on the right-hand side, various modern regional Atlantic Ocean surface water temperatures.
The second graph:
This is the view we are accustomed to seeing in the Climate Debate — the global surface temperature anomaly (some baseline — in this case 15 CE) with a starting point around 1850 (some start a bit later, 1890). Note that it is “Identical to Figure 1, but restricted to the years 1850−2015.” The starting point is picked to represent “the start of the Modern Industrial Era”.
Now an annotated version of the second graph:
Here we have the second graph 1850-2015, with the global Average Surface Temperature anomaly (again — baseline 15 CE) but I have dropped in a smaller window, on the left, bringing forward the Roman Warm Period and the Medieval Warm Period (MWP) — the years 100-800 CE (same scale) — to illustrate the difference between the peak Global Average Surface Temperature (GAST) of the Medieval Warm Period to the most current GAST on the graph (2015).
This exposes the ubiquitous trick of the Climate Debate, in which Global Temperatures are [almost] always shown only from the depths of the Little Ice Age (clearly marked on the first graph by Gebbie), resulting in images similar to Gebbie’s Figure 2 — despite the fact that most 2 millennia reconstructions clearly show the Roman and Medieval Warm Periods as generally in the same range as the Modern Warm Period. Given the acknowledged range of error in any temperature reconstruction and in modern estimates of global surface temperatures (today, in absolute temperatrures, around +/- 0.5ºC or a range of 1ºC) — there may be little, if any, significant-to-the-global-environment difference between the two periods.
The Medieval Warm period did not result in a “Climate Catastrophe” and the [iffy] little additional 0.2°C seen today is very unlikely to spark a modern Climate Catastrophe either.
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Author’s Comment:
A great deal of the polarization in the Climate Debate is based on this little trick of data presentation — using a starting date known to represent a low point in some data set of a measurement which the author wishes to show has increased to a present high. Failure to show the full context of the data is a type of data falsification.
Kudos to Geoffrey Gebbie for including both graphs in his paper.
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What I find a little disconcerting is the complete exclusion of submarine tectonic activity when ocean temperatures are discussed. It is assumed that all rising water temperatures have a solar origin. For example the Atlantic rift has been recorded pumping out cubic miles of methane gas, what else is it discharging? The latest information in geology circles is that tectonic activity occurring between New Guinea and the Solomon Islands initiates the El Nino cycle. The oceans make up 71% of the Earth’s surface and average depth is 4000 meters. We only have 3000 buoys covering millions of square kilometres and effectively know stuff all. I know all the money is in the study of atmospheric science and the “renewable industries”, but if there was a little bit of honesty in”climate science” then serious studies would be also looking at volcanic activity in the oceans and maybe the ‘renewables’ wouldn’t cost us the Earth.
Christine ==> Sorry for the delayed response — I started to do some research for papers on the topic — but was interrupted by real life.
There are studies on sub-oceanic volcanic activity. Such activity, as well as hot water vents, etc, do, of course, warm the ocean locally — they must — heat always always (almost) travels from warmer to colder.
AGW activist sites publish blog posts poop-pooping the idea that there is any measurable effect. Also see here.
We really know very little about ocean temperatures at the present time — in 20 or 30 years, we may have enough data to make some educated guesses about it.
I suppose this point is not new:
That the early data for the global temp readings will not have been an average of the recent 7 sources.
Would the readings from the period prior to 1870 be representative of just one or two of the 7 regions – rather than being a fair representation of the whole area?
If they aren’t comparable then the graph doesn’t show anything.
McBryde ==> The authors present the two as sort-of separate graphs – in Fig 1 — a double vertical line indicates both a change in time scale and a change from reconstruction of temps to “measured” temperatures.
One has to read the whole study to understand what they are getting at.
Atlantic warming since the Little Ice Age:
https://tos.org/oceanography/article/atlantic-warming-since-the-little-ice-age
Radiocarbon observations suggest that the deep Atlantic Ocean takes up to several centuries to fully respond to changes at the sea surface.
You would expect the deep ocean circulation with a cycle time of several millennia, to indeed respond slowly at depth to any changes at the surface. Not surprising that the data confirm this.
This does not stop alarmist scientists claiming that “missing” warming heat is somehow hiding in the deep ocean. That – miraculously – less than a century of surface warming is suffusing the abyssal ocean depths with disastrous warming.
This is like a cosmologist proposing that a part of the universe outside of our “light cone” is influencing earth. This is impossible – outside of our light cone, light cannot travel to earth during the history of the universe. As the R.E.M. song put it, “you can’t get there from here”.
The deep ocean is not in causal contact with the surface in real time. It takes centuries and millennia for changes of temperature and insolation at the surface to reach the deep ocean via changes in downwelling patterns.
Water in the deep ocean can be defined in n terms of “age” in years since its “formation” by downwelling from the surface. This age can reach 3-4000 years in places like the North Pacific.
The atmospheric nuclear bomb tests in the 1950’s and 1960’s have provided a valuable opportunity for a tracer study, using tritium (^3H, half life ) to directly map in 4D the Thermohaline circulation starting from the most important site of downwelling in the Northern Hemisphere, the Norwegian Sea.
If eddys from surface wind were mixing seawater down the the bottom, then deep water would not have this old “age” of thousands of years. In general the thermocline is a barrier to vertical mixing.
Alarmists snatching at the deep ocean as a place to domicile their missing warming, only shows that they are ignorant and contemptuous of oceanography.
The climate according to The Climate.
https://tinyurl.com/rktb35n
Epilogue:
This essay is just to highlight the paper of interest and point out this paper shows it was as warm in the past in the Common Era as it is now.
Some readers have pointed out that the paper’s reconstruction shows the Roman and medieval Warm Periods either conflated or with the MWP a bit early. While it is not my reconstruction — thus not mine to defend — I have supplied a link in Comments above (twice) that indicates that “reconstructions” are not measurements and that the generally disagree with one another — sometimes to a great degree.
Fussing about differing guesses as to past GAST, when we cannot adequately measure and calculate the present GAST, is a fools errand — nonetheless, it is interesting to see what different groups of researchers come up with.
Thanks for reading!
It’s not as bad as you suggest. Have a look at https://www.youtube.com/watch?v=v7OyfdWErfA and also the referred YouTube clips.
David ==> Steven Mosher sums up our ability to measure Global Average Surface Temperature:
“The global temperature exists. It has a precise physical meaning. It’s this meaning that allows us to say…The LIA was cooler than today…it’s the meaning that allows us to say the day side of the planet is warmer than the nightside…The same meaning that allows us to say Pluto is cooler than earth and mercury is warmer.”