New Paper: "Reconciling divergent trends and millennial variations in Holocene temperatures"

Guest post by David Middleton

This appears to be a fairly high resolution regional Holocene climate reconstruction of North America and Europe…

Reconciling divergent trends and millennial variations in Holocene temperatures

Jeremiah Marsicek, Bryan N. Shuman, Patrick J. Bartlein, Sarah L. Shafer & Simon Brewer

Nature volume 554, pages 92–96 (01 February 2018)

doi:10.1038/nature25464

Abstract

Cooling during most of the past two millennia has been widely recognized1,2 and has been inferred to be the dominant global temperature trend of the past 11,700 years (the Holocene epoch)3. However, long-term cooling has been difficult to reconcile with global forcing4, and climate models consistently simulate long-term warming4. The divergence between simulations and reconstructions emerges primarily for northern mid-latitudes, for which pronounced cooling has been inferred from marine and coastal records using multiple approaches3. Here we show that temperatures reconstructed from sub-fossil pollen from 642 sites across North America and Europe closely match simulations, and that long-term warming, not cooling, defined the Holocene until around 2,000 years ago. The reconstructions indicate that evidence of long-term cooling was limited to North Atlantic records. Early Holocene temperatures on the continents were more than two degrees Celsius below those of the past two millennia, consistent with the simulated effects of remnant ice sheets in the climate model Community Climate System Model 3 (CCSM3)5. CCSM3 simulates increases in ‘growing degree days’—a measure of the accumulated warmth above five degrees Celsius per year—of more than 300 kelvin days over the Holocene, consistent with inferences from the pollen data. It also simulates a decrease in mean summer temperatures of more than two degrees Celsius, which correlates with reconstructed marine trends and highlights the potential importance of the different subseasonal sensitivities of the records. Despite the differing trends, pollen- and marine-based reconstructions are correlated at millennial-to-centennial scales, probably in response to ice-sheet and meltwater dynamics, and to stochastic dynamics similar to the temperature variations produced by CCSM3. Although our results depend on a single source of palaeoclimatic data (pollen) and a single climate-model simulation, they reinforce the notion that climate models can adequately simulate climates for periods other than the present-day. They also demonstrate that amplified warming in recent decades increased temperatures above the mean of any century during the past 11,000 years.

Nature

I might just be willing to spend $20 to buy this paper… It’s behind the paywall, of course.

Naturally, the  University of Wyoming press release is alarmingly misleading:

University of Wyoming researchers led a climate study that determined recent temperatures across Europe and North America appear to have few, if any, precedent in the past 11,000 years.

What the paper says:

Although our results depend on a single source of palaeoclimatic data (pollen) and a single climate-model simulation, they reinforce the notion that climate models can adequately simulate climates for periods other than the present-day. They also demonstrate that amplified warming in recent decades increased temperatures above the mean of any century during the past 11,000 years.

“Amplified warming in recent decades” relative to centennial means doesn’t make the current climate unprecedented.

Furthermore, climate models can’t adequately simulate the present-day climate.

And they also appear to be using Marcott et al., 2013 as a benchmark.

Figure 1

Otherwise it looks like an interesting paper.  If I have time, I might dig into the extended data and supplemental information.

Feature image from NOAA.

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Richard M

So in other words we have many conflicting proxies. More unsettled settled science.

Javier

Don’t waste your money, David. It is pure and unadulterated BS.
Since models are unable to reproduce the cooling since the Holocene Climatic Optimum, here comes this happy group that based on a single pollen record (the most unreliable proxy) and a single model, claim that the Holocene was characterized by warming until 2000 years ago. Since this is not what most proxy records are saying, they claim that only the North Atlantic displayed cooling for 6000 years, while the rest of the world warmed. Of course they never mention why glaciers were growing all over the world for the past 5000 years, peaking at the LIA.
It is a real shame what they are doing at paleoclimatology with these on demand works that get the pre-decided answer and get published in Nature, that appears bent on following into Scientific American footsteps into irrelevancy. At least on climate issues.

Javier

And if you are interested in Holocene pollen reconstructions, I suggest you take a look at HOCLAT, the Holocene Climate Atlas.
http://www.oeschger.unibe.ch/research/projects_and_databases/web_based_holocene_climate_atlas_hoclat/index_eng.html
http://www.sritz.ch/resources/Research/HOCLAT.pdf
If you look at the figures in the pdf, you will see that using pollen records, you can essentially defend any narrative about Holocene climate. You just pick the records that support the narrative you want to push and ignore the others.
Marcott et al., did something similar with their proxy selection.
Two things speak clearly about what happened at the Holocene Climatic Optimum, glaciers, and treelines. None of them can lie as these shameful scientists do.

Marcott did something much worse to his paleoproxies in the Science paper, comprising clear academic misconduct. See second of two 2013 guest posts for Judith Curry, or essay A High Stick Foul in ebook Blowing Smoke, for the indisputable forensic evidence.

Greg

Oh , no! Not Make-up, Shake-un-Mix again. At least I give them full marks for humour with arranging the author list.

Bryan A

I’m thinking they start with their pre-determined answer they are looking for then mold their datasets to fit into their preconcieved idea while eliminating those that don’t fit. Other than perhaps laziness, it is the only real reason to have just a single proxy record and single model run. If they actually had 25 model runs and 24 diverged while 1 agreed, guess what…”We only have 1 model run.”

Javier

Well, it is understandable. Why do extra work if Nature has already told you it will publish it if you show the adequate result?

Renee

Any good “peer-reviewed” articles published recently? This one was interesting. http://www.mdpi.com/2225-1154/6/1/3/htm

Javier

Renèe, I was aware of that article and this other one:
Davis, W. J. (2017). The relationship between atmospheric carbon dioxide concentration and global temperature for the last 425 million years. Climate, 5(4), 76.
http://www.mdpi.com/2225-1154/5/4/76/htm
They are the creatures of Jackson Davis, whose story deserves to be told and known. He is a professor at UC Santa Cruz, and also the founder in 1981 of the Environmental Studies Institute (ESI). A well-respected environmentalist, he is also a scientist, and when the evidence became clear in not supporting the CO₂ hypothesis, he made a 180° turn that probably has costed him dearly.
“ESI continues its long-standing interest in climate change, although its focus has changed considerably. True to its dedication to evidence-based public policy, ESI analyzed the same paleoclimate records that formed the evidentiary basis of Vice President and Nobel Laureate Al Gore’s award-winning documentary “Inconvenient Truth” and discovered that the relation between carbon dioxide and global warming is more nuanced than previously thought. The results of this analysis are currently being peer-reviewed for publication and will be posted on this site following publication. If confirmed, ESI’s scientific findings will help point the way to a different, more adaptive, and more cost-efficient environmental policy response to climate change.”
http://www.environmentalstudiesinstitute.org/activities.html
Honesty in science and environmentalism. Both of his articles are interesting.

Ulric Lyons
Smart Rock

Their figure 1 seems to end at 500 years before present. Curious, and hard to reconcile with their statement about recent decades being warmer than anything in the Holocene. That statement sounds like the mandatory nod towards climate orthodoxy and may not be derived from their data.

Javier

They cut the figure because otherwise it would show Marcott’s hockey stick, that was so contentious than even its own authors disavowed it. It is in the Hall of Shame together with Mann’s hockey stick. So bad that instead of hiding the decline, they now have to hide the artificial spike.

tty

There is an even stronger reason. Continuing the pollen curve up to the present would be catastrophic. It takes decades to centuries for vegetation to react to climate, particularly trees, so a pollen curve would end on “Little Ice Age” temperatures.

Javier

I wrote a comment about HOCLAT that is m.i.a.
Take a look at the figures of the Holocene Climate Atlas based on pollen records. You will see why you can’t trust a reconstruction based solely on pollen records. You can essentially defend any Holocene climate narrative of your choice.
http://www.sritz.ch/resources/Research/HOCLAT.pdf

JimG1

The climate atlas you have provided would also seem to give credence to your previous point in the article regarding solar cycles that observation trumps mechanism, among other things.

observation trumps mechanism,
==≠======
except in climate science. co2 is the mechanism followed by billions of dollars to locate the observation to match.
over and over history has shown that nature. could care less about logic. just because it seems logical that heavier objects fall faster, nature routinely shows the whatever we believe is the mechanism, as we learn more we learn the mechanism is wrong.

tty

Whoever compiled that has no idea how inexact Holocene dating is. It is completely meaningless cutting the data up in 100-year slices. Very few of those proxies have that kind of time resolution (in practice only proxies with annual resolution, i e treerings and ice-cores, and even those are barely reliable at that level in the Early Holocene).

Yogi Bear

“… Although our results depend on a single source of palaeoclimatic data (pollen) and a single climate-model simulation …”
Isn’t this enough to disregard the whole thing?

Steve Keppel-Jones

That was my thought too. You were going to spend $20 on that?? It might not be quite at the level of Lew paper but I’d say pretty close!

Nah! It’s like just recycled Lew paper …

AGW is not Science

The Ministry of Truth lives!

A trend not consistent with sea level variation as well. Correlation on those time scales a must.

tty

The trouble with using pollen records for climate reconstruction is that plants migrate slowly and vegetation is therefore seldom in equilibrum with climate.
For example in the Early Holocene forests in Scandinavia were very largely birch and pine, suggesting a cold climate. However at the same time the treeline was several hundred meters higher than now, indicating a quite warm climate. The species indicating warmer climate (e. g. oak, beech, lime, elm etc) were still slowly expanding north from their ice-age refuges in southern Europe, so no warmth-indicating pollen.
Methinks it is not coincidental that this study uses a single very indirect and lagging proxy (=pollen) and avoids proxies that give more direct temperatures (Alkenone, Ice cores, TEX86, Treelines, Speleothems). These all show that temperatures were highest early in the Interglacial and have been sinking ever since.
By the way, it is well known and generally accepted that this is the pattern in every interglacial and if the climate models can’t match it, well then they are simply wrong.

michael hart

I was going to ask questions about the resolution and coverage of the details, and whether some idiot is going to extrapolate continental temperatures from oceanic proxies, but when I read “Marcott”, I just switched off.
At some point a person’s description has to switch from being a naive climate wannabe, to a climate crook. He should never be cited. From the point where he immediately published a paper, with the blessing of the unmentionables, the background for which was not included in his thesis shortly beforehand, he entered the world of politics. The science wasn’t there, and he knew it. And he knew his thesis committee wouldn’t like it.

Steve McIntyre

Promised data archive “The pollen reconstructions and simulation data that support
the findings of this study are available in the NOAA National Centers for Environmental Information Paleoclimatology Database https://www.ncdc.noaa.gov/paleo/study/22992“, needless to say, isn’t available as of now.

richard verney

It might be apt to post a picture, since pictures speak a 1000 words.
here is a photo of the Mendenhall Glacier retreat in Alaska revealing tree stubs from forests that grew one to two thousand years ago. Obviously it must have been very considerably warmer a couple of thousand years ago, because the ground is presently permafrost and there is presently no chance of a forest presently taking root.
http://www.drroyspencer.com/wp-content/uploads/Mendenhall-Glacier-tree-stumps.jpg

KTM

“amplified warming in recent decades increased temperatures above the mean of any century during the past 11,000 years.”
Their Figure 1 certainly doesn’t show that. I assume they’re pasting the thermometer record on the end of a pollen record, which is absurd on its’ face.
If pollen matches thermometers, then where is the modern spike? If pollen doesn’t capture the modern spike, then they can’t say anything about modern temperatures being extreme or unusual since they aren’t in the proxy.

ptolemy2

If data doesn’t match the models, change the data. Yawn.

Did a bit surfing after reading this and came across something in Wikipedia but only a reference to a Swedish book.
Apparently, before sudden cooling of the climate about 650BC, they grew grapes in the Nordic Bronze Age. The climate was supposedly as warm as central Germany and Northern France. Need a better reference but wondering how such a 97% consensus in archeology can get ignored by these anti-denialists.

Dave

I had thought that several recent Alps glacier paleo studies demonstrated that atleast one or more periods in the last 5000 years (certainly during the current Holocene), the extent of the glaciers were far less than today….in some areas completely gone. And remnants of alpine forests, etc have recently been uncovered as these glaciers have retreated since the LIA? I am a simple man so please excuse my attempts at sounding smarter than I am.

David S

If reality doesn’t match the models then reality must be wrong. /sarc