For those worried about tundra melt and methane outgassing, this study might dampen those worries a bit. A new peer-reviewed study by Clegg et al. demonstrates that modern global warming is significantly less than the global warming experienced in the higher latitudes, specifically Alaska, during the summers of the last 3,000 years. It demonstrates that the Current Warm Period (CWP) is not unprecedented, at least for Alaska. The authors suggest a tie in to solar variability.
From CO2 science:
What was done
The authors conducted a high-resolution analysis of midge assemblages found in the sediments of Moose Lake (61°22.45’N, 143°35.93’W) in the Wrangell-St. Elias National Park and Preserve of south-central Alaska (USA), based on data obtained from cores removed from the lake bottom in the summer of AD 2000 and a midge-to-temperature transfer function that yielded mean July temperatures (TJuly) for the past six thousand years.
What was learned
The results of the study are portrayed in the accompanying figure, where it can be seen, in the words of Clegg et al., that “a piecewise linear regression analysis identifies a significant change point at ca 4000 years before present (cal BP),” with “a decreasing trend after this point.” And from 2500 cal BP to the present, there is a clear multi-centennial oscillation about the declining trend line, with its peaks and valleys defining the temporal locations of the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period, the Little Ice Age — during which the coldest temperatures of the entire interglacial or Holocene were reached — and, finally, the start of the Current Warm Period, which is still not expressed to any significant degree compared to the Medieval and Roman Warm Periods.
C3 Headlines provided an annotated and reversed graph which you can see below:
The paper title is published in Quaternary Science Reviews
Here’s the abstract:
Six millennia of summer temperature variation based on midge analysis of lake sediments from Alaska
Benjamin F. Clegg, Gina H. Clarke, Melissa L. Chipman, Michael Chou, Ian R. Walker, Willy Tinnere and Feng Sheng Hu
Abstract
Despite their importance for evaluating anthropogenic climatic change, quantitative temperature reconstructions of the Holocene remain scarce from northern high-latitude regions. We conducted high-resolution midge analysis on the sediments of the past 6000 years from a lake in south-central Alaska. Results were used to estimate mean July air temperature (TJuly) variations on the basis of a midge temperature transfer function. The TJuly estimates from the near-surface samples are broadly consistent with instrumental and treering-based temperature data. Together with previous studies, these results suggest that midge assemblages are more sensitive to small shifts in summer temperature (
0.5 °C) than indicated by the typical error range of midge temperature transfer functions (1.5 °C). A piecewise linear regression analysis identifies a significant change point at ca 4000 years before present (cal BP) in our TJuly record, with a decreasing trend after this point. Episodic TJuly peaks (14.5 °C) between 5500 and 4200 cal BP and the subsequent climatic cooling may have resulted from decreasing summer insolation associated with the precessional cycle. Centennial-scale climatic cooling of up to 1 °C occurred around 4000, 3300, 1800–1300, 600, and 250 cal BP. These cooling events were more pronounced and lasted longer during the last two millennia than between 2000 and 4000 cal BP. Some of these events have counterparts in climatic records from elsewhere in Alaska and other regions of the Northern Hemisphere, including several roughly synchronous with known grand minima in solar irradiance. Over the past 2000 years, our TJuly record displays patterns similar to those inferred from a wide variety of temperature proxy indicators at other sites in Alaska, including fluctuations coeval with the Little Ice Age, the Medieval Climate Anomaly, and the First Millennial Cooling (centered around 1400 cal BP). To our knowledge, this study offers the first high-resolution, quantitative record of summer temperature variation that spans longer than the past 2000 years from the high-latitude regions around the North Pacific.
Here’s an excerpt from the conclusion:
Within the limit of chronological uncertainties, some (but not all) of these cooling events at Moose Lake coincide with periods of reduced solar irradiance, such as the solar minima centered on the middle and late LIA (250 and 100 cal BP), 1400 cal BP, and 3400 cal BP (Steinhilber et al., 2009).
Although the co-occurrence of solar minima with cooling during the LIA is well appreciated, the role of solar output in modulating surface temperature remains controversial, partially because the effect of solar activity changes on the surface energy budget is orders of magnitude lower than those of the drivers operating over shorter timescales (e.g., clouds or volcanism) (Damon and Peristykh, 2005). Nonetheless, a number of recent paleoclimate
studies have attributed decadal- to millennial-scale variation to fluctuating solar irradiance in Alaska (Hu et al., 2003; Wiles et al., 2004; Tinner et al., 2008) and elsewhere (Hegerl et al., 2003; Damon and Peristykh, 2005; Eichler et al., 2009). Thus the potential role of solar irradiance in high-latitude climate change remains an issue that warrants further research (MacDonald, 2010). Analysis of midge assemblages in lake-sediment cores
from other sites is necessary to verify our results from Moose Lake and assess the potential linkages of summer temperature variation to fluctuating solar output.
The full paper is available at the Willie Soon’s website at Harvard here (PDF)
Addendum:
Some commenters point out that I did not include this caveat from the paper:
The Moose Lake TJuly record is of limited value for assessing anthropogenic warming in the context of the long-term natural variability because of the relatively coarse temporal resolution and potential impacts of human activity on the lake chemistry. The youngest sample of the record spans the period of AD 1968-1972, falling within the cooler interval of the 20th-century in Alaska (Chapin et al., 2005).
And they have a point, I should have included this. So I’m rectifying that now. They also say:
The inferred TJuly from this sample (13.76 +/- 1.43 °C) compares favorably with the mean of instrumental
July temperatures of the same period (13.77 +/- 1.13 °C,
corrected for a dry adiabatic lapse rate of 9.80 °C per km) as
recorded at a nearby weather station (Gulkana Airport). The relatively coarse resolution of the Moose Lake midge record, along with the brevity of weather-station records from our study region (w50 years), precludes a further assessment of our midge-based TJuly estimates through comparison with instrumental climate data.
However, the midge TJuly estimates of the past 350 years (Fig. 4A) can be compared with treering temperature estimates of the same period from tree line sites in the Wrangell Mountains (Davi et al., 2003; Fig. 4B). In general, the midge temperature inferences parallel the treering temperature patterns. For example, the two records exhibit similar magnitudes of climatic warming after the Little Ice Age (LIA) and both capture low temperatures corresponding to the middle and late phases of the LIA, which also coincide with local advances in valley glaciers within the Wrangell Mountains (Wiles et al., 2004). However, the specific peaks and troughs do not always match between the two records, which is expected given the chronological uncertainties associated with our 210Pb ages and with the age-depth model for samples older than 64 cal BP.
These results contribute to a growing body of evidence
demonstrating the utility of midge assemblages for reconstruction of relatively small TJuly variation on both historic and Holocene timescales (e.g., Heiri et al., 2003; Larocque and Hall, 2003). Together, these studies indicate greater sensitivity of midge assemblages to TJuly variation than implied by reported error envelopes of midge temperature transfer functions.
Clegg et al thinks that the TJuly agrees with a local instrument record, some tree-ring study, and suggest TJuly signal is greater than the error bands. However, this brings up an interesting point.
In a similar midge-paleo study covered on WUWT (Yarrow et al 2009, PNAS, full PDF here, CU-Boulder press release here) the authors of that study say in the press release that:
…changes seen in the sediment cores since about 1950 indicate expected climate cooling is being overridden by human activity like greenhouse gas emissions.
So we have one study, Clegg et al saying that this midge-paleo is too coarse to use for AGW signal determinations, and another similar study Yarrow et al saying midge-paleo (with others) does have enough resolution and it shows a modern impact of humans emitted GHG. Quite the contradiction.
In the Yarrow et al Baffin Island study, they do in fact look at more recent core data than the Clegg et al Alaska lake study. In reading the Clegg et al study, they say:
The youngest sample of the Moose Lake midge record (from 3.0 to 3.5 cm core depth; we did not have adequate amount of sediment from 0 to 3 cm for midge analysis) encompasses sediment deposition of AD 1968-1972.
Yet, in the Yarrow study they apparently did have enough sediment to make a determination and then claim that it shows unprecedented warming and human influence. Interestingly though, they cite a “statistical uncertainty of 2.2 °C”
As with any transfer function, chironomid-inferred temperatures contain some statistical uncertainty (14, 34). Although absolute temperature values have a statistical uncertainty of 2.2 °C, reconstructed trends in past temperature at this site are likely robust because the amplitude of these trends exceeds the statistical uncertainty of the model; furthermore, these trends are supported by many other proxies from the region (36).
So they also compared to other proxies. I find it odd though that Yarrow says this in the CU-Boulder press release here, emphasis mine:
But the cold-adapted midge species abruptly began declining in about 1950, matching their lowest abundances of the last 200,000 years. Two of the midge species adapted to the coldest temperatures have completely disappeared from the lake region, said Axford.
This seems to point to a sample problem for recent layers such as Clegg et al lament. I wonder what chironomid data Clegg et al had from 1972 forward and why they deemed it insufficient.
Apparently though, the lack of certain species wasn’t a problem for Yarrow et al, and they used that to bolster the claim that human caused warming was reflected by that species loss. I pointed to the fact that in Alaska and Canada, post World War II DDT use for mosquito control was the norm, so perhaps the lack of modern midges was a consequence of that DDT use in both cases. It is an uncertainty.
I’m reminded though of the Mann-Briffa Yamal tree ring debacle, where if that data didn’t fit near the present, you throw it out post 1960 and splice on the instrumental temperature record. Yarrow’s insistence that the cold species midge disappearance implies human caused warming is on par with the leap of “Mikes’ Nature trick”. Both ignore other potential influences.
While some commenters complain about the lack of Clegg et al data since 1972, the same posters IIRC did not complain about the proxy data truncation at 1960 and substitution of post 1960 instrumental data in Mann-Briffa’s studies.
While the lack of a useful sample post 1972 may simply be the lake biology, I think I’ll ask Clegg why they decided the post 1972 sample was insufficient and why Yarrow et al 2009 wasn’t referenced in the context of the modern midge data sample, and if they reply, and post a follow up note here.
I’ll close by pointing out Clegg et al’s closing sentence:
Analysis of midge assemblages in lake-sediment cores from other sites is necessary to verify our results from Moose Lake and assess the potential linkages of summer temperature variation to fluctuating solar output.
Replication is the basis of science, it is good to see them calling for that.
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I’ve been reading a couple of archeology subscriptions for 35+ years. This study is in line with decades of similar findings. tonyb‘s links are perfect examples.
Gneiss says:
“”Me, I’ve been doing a whole bunch of other things while just occasionally dropping by to post a reality-check note at WUWT.””
Wow. Could this guy be any more condescending?
Gneiss is avoiding the fact that guys like Trenberth, Mann, Hansen, and the rest of the climate alarmist tax eaters refuse to have any kind of a public conversation with skeptics. That means they don’t have confidence in their claims, which are constantly shown to be based on faulty computer models and an adjusted temperature record.
The final straw for me was Trenberth’s plan to replace the null hypothesis with his own. But trenberth doesn’t own the climate null hypothesis, it’s been used by climatologists and meteorologists for longer than Trenberth has been around. Whenever someone says “It’s the warmest it’s been since 1880” (or whatever year) they are making use of the null hypothesis. It shows that the temperature was higher in the past.
Really, there’s nothing to show that the climate now is any different at all than it’s been in the past. How about that, Gneiss?
KD, the fact is that newer methods are more accurate than midges, and a reason for leaving them off a graph of historical temperature is often just to hide the incline, which I mentioned earlier is quite substantial in Alaska and is relevant to this discussion thread, even if not the original paper.
re post: bubbagyro says: January 29, 2011 at 10:14 am
Bubbagyro, meta-analysis, done properly, can be powerful as you note. The devil is in the details however, and meta-analysis are generally far less reliable than individual well done studies. With meta-analysis, it is far too easy for inappropriate selection or groupings of studies to occur, or for researcher bias to be introduced, cherry-picking of which studies to include or exclude, etc. Every possible error for an individual’s work can be introduced into a meta-analysis, plus errors associated with the selection and groupings. As a result, it behooves one to always look at meta-analysis with a very very skeptical eye. It used to be that meta-analysis results and studies were automatically somewhat looked down on because it is far easier to research and massage other researcher’s data and work than it is to actually get into the field or the lab and do one’s own original work – even when perhaps that work is validating another researcher’s work.
Then you throw on top of all these problems that exist even with relatively simple meta-analyses looking at the identical type of research at least, with all the problems associated with trying to do something of this nature using research of different types of proxies, from different regions of the world, which may have had climate changes at slightly different time periods, along with the issues of possible timing lags or errors associated with each type of proxy, etc., etc.
It’s entirely possible that even a reasonably well done meta-analysis of this sort would wind up giving utterly incorrect results.
To all of Gneiss’s comments:
Gneiss, saying that something is so doesn’t make it so. Readers of this website, and of Climate Audit, know all the tricks and denials that Michael Mann and company have used to try to keep their sinking ship afloat all these years. I don’t know if you have followed what Steve McIntyre has found over the last 6 years or so of pursuing the data Mann would not share, and of analyzing it when he found it.
If you really believe that Mann and the Hockey Team’s efforts have:
* used appropriate statistical tests, and have passed them; and
* that there was nothing wrong with their using the upside down Tiljander series to show warming when they had been warned that (1) they was using it upside down, and (2) the series was contaminated by 20th C activities, but they used it anyway;
* that the use of a very small subset of the sample of trees from Yamal was appropriate when the use of the entire series would have shown opposite results contra to the hockey stick;
* that it was appropriate for members of the “team” to try to keep McIntyre’s accurate reviews out of print even if they had to “change the meaning of peer review” (a quote from Phil Jones in the Climategate emails);
* that it is OK to use hockey sticks so non-robust that they depend on just two of many tens of tree ring series (western US bristlecones and a select series from Yamal) are acceptable temperature records when exclusion of these two series makes the hockey stick disappear;
* that it is OK to truncate the tree ring record when it shows declines in temperatures after 1960 and to then “hide the decline”, but it is then also OK to use tree ring records after 1960 when they show an increase (the Yamal trees, but only the small part of the series that does show an increase, when the larger series does not)….
If you believe these things, then you need to go to Climate Audit and do some searches and understand these issues better than it seems you do.
But you may be doing something different here. You may just be trying to blow smoke. Politicians have a phrase that describes some of what they do: “Perception is reality.” Keep repeating something, and eventually it becomes perceived truth. That is what the global warming machine had been doing, successfully, before Climategate. It is a little harder now, but I sense that the climate change perdition community is still trying to create a perception that everything is going to hell in a handbasket unless we do what the IPCC says we should do.
I’m wondering which of these you are — someone who hasn’t actually explored all the work that McIntyre and company have done to show how bogus the hockey stick record is? In other words, a victim of not reading both sides? Or someone who is just being political, not scientific, and is blowing smoke at us?
Ummm……
As Anthony appears to be too humble to mention it, he has added an addendum (very well written) to his original post.
Well worth the read.
John writes,
“But you may be doing something different here.”
You give me too much credit, I’m not nefarious or tricky. I was trying to get Anthony and others to actually read, and honestly describe, the article that his post was about . Initially he had not done so, but I see that he subsequently rewrote his original post. So in that sense my work here was successful.
As for persuading any of the regulars here of what most scientists believe, that AGW is real, I have no illusions about the prospects for that.
This is a good article.
I am glad we are getting past the “proxies are evil” idea.
@ur momisugly Gneiss
Talks about the signature run-up of modern global warming. Hug? What has he been smoking? That implies there’s something unique here and there clearly isn’t.
@Kirly
I also eyeball a trend over the last 4000 years or so that warm intervals are geting shorter and cold intervals longer.
@ur momisugly R. Gates
You say, “Indeed, since the bulk of the 20th century warming occurred after that date…” (late 60’s). Are you daft, or deliberately disingenuous? Actually, only the bulk of the second half of the 20th century’s warming occurred after that date. You completely ignore the warming that occurred in the first half of the 20th century, of nearly equal magnitude, followed by cooling.
Note the similarities of this graph to that constructed almost a century ago by Elsworth Huntington from red wood tree rings and the levels of Owen Lake:
http://enthusiasmscepticismscience.wordpress.com/global-temperature-graphs/1924_huntington_civilizationandclimate_p321/
MWP and Roman peaking are vaguely aligned, as are the dark ages troughs. At that time global climatology was mostly looking to measure warm-dry to cool-wet variations and it saw rainfall as the key factor. In his work in the 1960s & 70s Hubert Lamb developed on earlier research (including by Huntington) concerning marked variations in the 14th and 15th centuries (Black death and early Renaissance). Most notable was that there seem to be some very wet (& cool??) periods that impacted negatively on civilisation in northern climes. While Huntington, Lamb and Clegg all note wide variation in this pre-LIA period, Huntington’s climatic optimum/min graph here runs in reverse of what Lamb and Clegg find for temp variation in Central Eng and Alaska respectively. Generally, I have found data on this period most varied and contradictory.
I like tree-rings, bugs bite.
Rob Wilson et al 2006: Cycles and shifts: 1,300 years of multi-decadal temperature variability in the Gulf of Alaska. PDF
Lot of trolls stopping by.
The hoped for purge, by the new congress, of the thousands of scientists wasting taxpayer dollars studying settled science can’t already be filling the troll rolls, can it?
Gneiss
Go out in the streets of New York or Dublin and tell people global warming is happening. You’ll find a reality check.
Mike’s Nature trick—something this study didn’t use. 🙂
Gneiss says:
“As for persuading any of the regulars here of what most scientists believe, that AGW is real, I have no illusions about the prospects for that.”
The “regulars” here come in all sizes. There is no censorship of views here, as there most certainly is at realclimate, climate progress, etc. I have yet to get a single comment past moderation at those blogs.
And FYI, neither I nor most here have ever taken the position that AGW is non-existent. The problem is that alarmists want to make AGW significant, when there is zero evidence that CO2 has ever caused any global harm. Evidence shows that the AGW effect is too minor to bother with.
I will stand corrected if you can produce testable, empirical evidence showing that CO2 — specifically — has caused global damage. Having asked this question of alarmists numerous times, they have come up with exactly *zero* evidence that CO2 causes global harm.
Conclusion: More CO2 is harmless, and it is beneficial to the biosphere. The sooner you understand that, the sooner the scales will fall from your eyes. CO2 is life – and the biosphere is starved of it. More is better; there is no downside.
Speaking of the poor science found in Mann’s Hockey Stick:
Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium”….
National Academy of Science report on the Mann Hockey Stick, page 4
http://www.nap.edu/openbook.php?record_id=11676&page=4
“There is no censorship of views here”
Of course there is, Smokey, do you honestly not know that?
Anthony Watts says:
REPLY: No you aren’t confused. Neither am I. Dr. Mann et al is a different matter altogether. I’m glad you have come to the conclusion that Mann’s work suffers from the same sort of uncertainty problems. There may be hope for you yet.
As the authors point out, more lake studies are needed to confirm, and as more studies are done, the confidence may increase, or the study may be disproven. It would behoove Mann et al to take the same path, rejecting those 12 trees in Yamal as an insufficient and perhaps cherry picked sample (YAD061) and run the full Schweingruber set and see what they get. – Anthony
More lake studies have already been done, and analysis of 6 of them shows a different relationship between modern temperatures and the MWP in the Arctic, including some lakes in Alaska. This doesn’t agree with the conclusions from the above study involving midges.
http://www.pages-igbp.org/products/newsletters/2009-1/special%20section/science%20highlights/Kaufman_2009-1%2810-11%29.pdf
High-resolution records
Of the new proxy records, six are resolved at sub-decadal to annual scale, including four based on varve thicknesses and two on biogenic-silica content (Fig. 2). They were calibrated using instrumental climate records to develop regression models to infer numerical values of past summer temperature downcore. The temperature variation for these records averages ± 0.73°C (1σ). Stacking the records by binning the data into 50-year intervals, normalizing each to a mean of zero and a variance of 1σ, then averaging the values for each bin reveals a coherent structure to the time series. Most striking is the most recent half-century, which exhibits the single highest average normalized temperature values and a shift to higher temperatures that is twice as large as any other consecutive interval during the last 2 kyr
Gneiss says:
January 29, 2011 at 4:02 pm
..”As for persuading any of the regulars here of what most scientists believe, that AGW is real, I have no illusions about the prospects for that.”
=======
Persuasion and beliefs, have no place in science.
A proof of your term “real”, is requested.
Otherwise, I usually enjoy reading your comments.
Amino, let’s add back in some of the rest of that quote.
Why did the National Academy of Sciences have low confidence in Mann’s 1999 conclusion that the 1990s were the warmest decade, and 1998 the warmest year, in a millennium?
because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales.
So, other scientists thought Mann overconfident about that decade and year. But what did they think regarding longer timescales?
The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on icecaps and the retreat of glaciers around the world, which in many cases appear to be unprecedented during at least the last 2,000 years. Not all individual proxy records indicate that the recent warmth is unprecedented, although a larger fraction of geographically diverse sites experienced exceptional warmth during the late 20th century than during any other extended period from A.D. 900 onward.
Gneiss says:
January 29, 2011 at 1:37 pm
“Hah, Fred and I are the only ones here who actually looked at this study to find out what it said. You’ve got reality backwards. Looks like a fine study to me. Have you read it?”
Son, this forum is for discussion of issues. If you have an argument to make, make it. State it in your own words. If you do not state it in your own words, I conclude that you do not have the ability to do so. I stop reading you.
If you need to send us to an article, you are presuming to assign homework. In that case, I conclude that you are a third-grade school teacher whose disguise is not yet perfected.
Gneiss,
Whose views are censored here? Name names.
And the NAS statement has been debunked here so many times I’ve lost count. Prof Richard Lindzen lays out chapter and verse about how these organizations have been co-opted by radical CAGW advocates. And he, I think, knows more about it than you do.
Anyone who buys into the ridiculous Mann Hokey Stick’s flat handle [no MWP or LIA] has drunk the True Believer Kool Aid. In addition to ice core proxies — accepted as being the best proxies for the geological record, there are numerous proxies all over the world that verify the MWP.
The fact of the MWP sticks in your craw, doesn’t it? Because with a warmer MWP, current temperatures are nothing unusual, and your cAGW fantasy goes down in flames.
“The fact of the MWP sticks in your craw, doesn’t it? ”
Not at all, Smokey, you’re imagining that. The MWP appears prominently in some data that I work with, and some articles I have written.
[ why not share one of your articles with us then? ~mod]