Guest Post by David Middleton
The Gorebots are all atwitter about this new paper…
Science 8 March 2013:
Vol. 339 no. 6124 pp. 1198-1201
DOI: 10.1126/science.1228026
A Reconstruction of Regional and Global Temperature for the Past 11,300 Years
Shaun A. Marcott, Jeremy D. Shakun, Peter U. Clark, Alan C. Mix
Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time. Here we provide a broader perspective by reconstructing regional and global temperature anomalies for the past 11,300 years from 73 globally distributed records. Early Holocene (10,000 to 5000 years ago) warmth is followed by ~0.7°C cooling through the middle to late Holocene (<5000 years ago), culminating in the coolest temperatures of the Holocene during the Little Ice Age, about 200 years ago. This cooling is largely associated with ~2°C change in the North Atlantic. Current global temperatures of the past decade have not yet exceeded peak interglacial values but are warmer than during ~75% of the Holocene temperature history. Intergovernmental Panel on Climate Change model projections for 2100 exceed the full distribution of Holocene temperature under all plausible greenhouse gas emission scenarios.
Marcott et al., 2012 is behind a paywall; however the supplementary materials include a link to their proxy data.
This paper appears to be a text book example of creating a Hockey Stick by using a low resolution time series for the handle and a high resolution time series for the blade…
Let’s test one of the 73 proxies.
I picked ODP-1019D, a marine sediment core from just offshore of the California-Oregon border because it has a long time series, is a an annual reconstruction and has a nearby long time series instrumental record (Grants Pass OR).
ODP-1019D has a resolution of 140 years. Grants Pass is annually resolved…
Let’s filter Grants Pass down to the resolution of the Marcott et al. reconstruction…
Grants Pass sure looks very anomalous relative to the rest of the Holocene… Right?
Well, not so fast. ODP1019D only has a 140-yr resolution. The record length at Grants Pass is less than 140 years. So, the entire Grants Pass record would be a single data point in the ODP-1019D record…
While, the most recent ~140 years might be warmer than most of the rest of the Holocene in this particular area, does anyone else notice what I did?
The Grants Pass/ODP-1019D area has been warming at a fairly steady rate for 6,500 years…
I don’t know how many of these proxies I will have time to analyze… Probably not very many. Maybe this could become a WUWT crowd-sourcing project.
Title revised per notes below, 03-11-2013. Mod]
@- elmer
Excuse my ignorance but what annual event off the coast of Oregon creates layers of sediment that accurately measure temperature?
Summer.
It’s not annual an annual event, like a varved lake bed. It’s the continuous deposition of shells of forams, nanofossils and other critters. The stable isotope concentrations of several elements are effectively geochemical thermometers.
This particular core has a resolution of about 140 years. The average deposition rate was ~0.5 mm/yr. The core was sampled every 5-10 cm (50-100 mm). So each sample represented 100-200 years of deposition.
You have to ask if the science is has settled has claimed , and the situation as urgent has we are told, given ‘climate doom’, why the authors did no make this research freely and easily available rather than have it hide behind a pay-wall . That way the majority of the people could access it and given its ‘settled ‘ all they really could do is admire it anyway so its not has if they have to fear having errors found is it ?
But call me sceptical, but I cannot help but feel that if the situation was has they claim it to be , they would make a lot more effort to get the research , included the data out there to has many people has possible , for after all its about ‘saving the planet ‘
When I look at that Marcott graph of temperature over the last 11,000 years, I see a huge warming period when CO2 levels were very low. Wonder how that happened?…
izen says:
Summer.
Thanks that explains everything.
The money quote is in the supplement where it talks about the transfer function gain (relationiship) between the real signal and the sampled / estimated signal of the real signal.
“The gain function is near 1 above ~2000-year periods,
suggesting that multi-millennial variability in the Holocene stack may be
almost fully recorded. Below ~300-year periods, in contrast, the gain is
near-zero, implying proxy record uncertainties completely
Marcott et al., 2012 24 remove centennial variability in the stack. Between these two periods,
the gain function exhibits a steady ramp and crosses 0.5 at a period of ~1000 years.”
There you have You can not resolve . componets / events below 300 years in the output as they are swamped by the noise/uncertainty.
@- David Middleton
“This is why the people who reconstruct plant stomata CO2 chronologies control for sunlight, precipitation and other environmental factors.”
A key environmental factor that alters plant stomata is temperature.
So what temperature record do the people who reconstruct plant stomata CO2 chronologies use as the control data?
The Marcott-et-al-2013 reconstruction perhaps…..
@-“δ14C has also been highly variable throughout the Late Pleistocene and Holocene.”
Holocene C14 has highly varied by about 3% from cosmic ray variations.
There is no sign of the sort of variations that would indicate significant changes in total atmospheric carbon since that seen during the melt from the last glacial period.
Confirmation bias may be at work here.
http://www.sciencedirect.com/science/article/pii/S0277379113000553
Stomatal proxy record of CO2 concentrations from the last termination suggests an important role for CO2 at climate change transitions
Hank: “Studying the proxies, I discovered that only nine of the 73 proxies contained data that extended to 1950. Of those nine, only two contained data that extended to 2000.”
So, Marcot et al claim what they claim on the basis of two proxies!?! And even those two appear to be cooling in the later part of the 20th century!
There is no evidence that temperature variations affect stomatal densities under natural growth conditions and have rarely exhibited effects on stomatal densities in controlled experiments.
Temperature variations do not affect stomatal frequencies (stomatal index).
See Figure 1 of Marchal, 2003.
δ14C dropped from about 90‰ to about -25‰ from ca. 5500 BC (~7500 yrs. ago) to ca. 500 AD (~1500 yrs. ago), then climbed to about 15‰ by the 1800’s. The recent δ14C depletion is no more anomalous relative to the rest of the Holocene then the δ13C depletion is.
Hello Ivan, yes, that’s correct. All nine proxies extend to 1960, eight extend to 1980, seven to 1990, and two to 2000. There was a slight typo in the text of my article. It should have said nine proxies that extended past 1950. For statistical reasons, it was the ones that extended past 1950 that were the focus of my analysis.
I wonder if there’s an email out there saying, “We’ve got to get rid of the Holocene Warm period…”
Re izen says: March 12, 2013 at 9:24 am
David Middleton says: March 12, 2013 at 9:36 am
elmer says: March 12, 2013 at 11:00 am
Hope I haven’t left anyone out. Another complexity in interpreting sediment data is “bioturbation”, or the churning of the top layer of sediment by benthic creatures. If I recall correctly, that would be about the top 10 centimeters or so. The bioturbation induces an averaging over the number of years based on bioturbation depth divided by sedimentation rate.
I thought the 8.2kyr event was the fastest fall and rise in temperature through the Holocene?
There have been multiple fast rises and falls since the last ice age, documented in high resolution high quality spelethemes. And these events have been global as they have been found synchronized in various locations around the world. The recent rise is not exceptional, neither in its time frame nor in its extent.
“However, the spike of the last century does have special status, apart from being well observed.”
Hmmm… this pretty accurate. The portion of the squiggly line drawings that resemble a spike have indeed been well observed.
The evidence that the spike resembles any kind of reality in any way, has not.
Andrew