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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The fluctuations in the reconstructed temperatures are smaller than the uncertainty in the reconstruction estimated by the root mean squared error of prediction. The reconstruction should therefore should be interpreted with caution.
REPLY:McIntyre and McKittrick and later McShane and Wyner pointed out similar caveats with the Mann hockey stick, yet for some people it is cautionless gospel.
Also, note the last sentence in their conclusion:
“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.”
Mann could have saved us all a lot of trouble if he’d been as cautious.
– Anthony
Clarify for me BP. I thought that some of the BP were just people trying to get away from BC and BP and BC zero were the same. This graph BP zero is 1990-2000.
If some one sees this graph 500 years from now how will they understanding the time perspective? Or did I misinterpret?
Methane outgasing is not too much of a problem for climate but the breakdown of methane requires oxygen. Previous anoxic events, that caused species extinction, have been thought to be caused by the oxidation of excess methane in the atmosphere.
I neve thought those pesky midges could ever serve any useful purpose. It just goes to show, we can all make false assumptions.
I wonder how the “Team” will discredit this one.
Please stop this cherry picking!
[please stop impersonating Paul Nurse, since I assume you are not really him. it is noted you use other names with this email address ~jove, mod]
Wow. If these results are confirmed it is dynamite. Just as many have been arguing the warmth is not unprecedented and the rate of warming is not unprecedented. In fact the current period could not look much more ordinary. So the climate scientists say there is no possible explanation for the current warming without CO2. I think they had better think again.
The correlation with the skeptics view of the real historical picture is amazing. If such a neat picture had come from the AGW camp I would have dismissed it as being too good to be true. I hope it is not in this case!
I would have liked to know the error bars on the temperature and also the temporal resolution but the sensitivity of 0.5C and the fact that successive summers can presumeably be counted suggests that both of these will be easily accurate enough for the purpose. Looks like great research.
“a midge-to-temperature transfer function that yielded mean July temperatures”
——————————————————————-
The only midge-to-temperature transfer function I am aware of is when the buggers bite you and your temperature goes up trying to swat them.
Even the cheesiest science fiction doesn’t strain credibility this much.
Telford is right. We should look with caution on any proxy reconstruction until it has been [truly] independently verified.
REPLY: Note the last sentence of the conclusion, the authors ask for independent verification – Anthony
@ur momisugly johanna:
Funny how insects in sediments are credible when they imply 20th century warming is unique. Stop the presses 😉
http://www.colorado.edu/news/r/fa189a8186a324d8f62b5d55ba4b8969.html
An analysis of sediment cores indicates that biological and chemical changes occurring at a remote Arctic lake are unprecedented over the past 200,000 years and likely are the result of human-caused climate change, according to a new study led by the University of Colorado at Boulder.
The research team reconstructed past climate and environmental changes at the lake on Baffin Island using indicators that included algae, fossil insects and geochemistry preserved in sediment cores that extend back 200,000 years.
Anthony writes,
“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.”
I don’t see anything resembling this claim in their paper. For one thing, their chronology ends in 1968-72, a relatively cool period in Alaska, so it misses the signature run-up of modern global warming (since 1975). For another thing, the authors are cautious about possible affects of 20th-century human disturbances, notably dam building, on their Moose Lake site. Here’s what they actually say:
“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 [citations].”
REPLY: OK let’s say the 1930’s dust bowl warm spike (that it does catch) doesn’t matter either. That still leaves the question of how does the previous episodes of warmth happen without all our “modern” CO2. BTW where were your complaints about Mann and Briffa ending their series in the 1960’s?
Note the green line.
– Anthony
did you miss this bit?
REPLY: Did you miss this?
We covered it here earlier.
Funny how the high latitude midges can be usefull to prove human caused warming in one study and they can’t possibly in another. – Anthony
REPLY:McIntyre and McKittrick and later McShane and Wyner pointed out similar caveats with the Mann hockey stick, yet for some people it is cautionless gospel. – Anthony
I seem to be confused. Isn’t this saying that the very report you are praising has the very problem you are highlighting?
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
Jarmo says:
January 29, 2011 at 7:36 am
@ur momisugly johanna:
Funny how insects in sediments are credible when they imply 20th century warming is unique. Stop the presses 😉
========================================================
lol, beat me too it! While I’m as skeptical about bugometers as I am treeometers, I am a firm believer in “what’s good for the goose is good for the gander.” Anthony’s first post on this reveals this typical mindset. Its only proof if it shows warming, else error bars, cherry picking, and incredulity are invoked.
Well.. this blows more holes in the pro-AGW crowd’s claim that the RWP and MWP were “local phenomenons” for Europe or simply didn’t exist (the Yamal siberian tree study).
Has there been any significant research to show that the two warm periods also affected the Southern hemisphere as well?
This seems like an excellent study, and the authors are correct to point out similarities between their midge record and other records using other proxies.
One such study that they may mention in the body of their paper, but I didn’t see in the Abstract, is the record WUWT highlighted several months ago, showing that Greenland was considerably warmer about 6 to 8 thousand years ago, and has gotten cooler since, with peaks and valleys of temperatures at roughly the same time periods (LIA, MWP RWP) as in this record. The Greenland record used different proxies for temperatures, so now we have two roughly equivalent temperature records from two different parts of the Arctic using two different proxy indicators for temperatures. Thank goodness the proxies weren’t tree rings, or we would be back in the Mannian swamps….
One other thing to think about: if the gradual reduction in temperatures in the last 6 thousand years in the Arctic really is related less to the centuries-scale differences in the strength of the sun, but rather to a longer time period relationship of the earth’s orbit around and tilt in regard to the sun, then this may provide evidence for how the earth goes from interglacials such as we are in (the Holocene) into the next ice age.
And if that is the case, and this study and others provide some evidence that we are on the way to another ice age, then maybe we should consider the wacky argument that CO2 is keeping us out of the next ice age with a little more thought? I’m not yet on that bandwagon, but I’d like to see more paleoclimatologies think about it seriously.
On the other hand there is this new Science paper by Spielhagen et al. also linked from RC
http://climateprogress.org/2011/01/27/science-temperatures-atlantic-water-arctic-unprecedented-2000-years-linked-to-arctic-amplification-of-global-warming/
Basically the hockey stick is revived for the North Atlantic.
Anthony writes,
“McIntyre and McKittrick and later McShane and Wyner pointed out similar caveats with the Mann hockey stick, yet for some people it is cautionless gospel.”
McIntyre and McKittrick and later McShane and Wyner are cautionless gospel on many blogs. But they have not held up at all to scrutiny by scientists or statisticians who tried to replicate their results.
Mann’s hockey stick, on the other hand, has held up to replication very well. Similar blades of steep recent warming have been seen now in scores of studies done by other research teams using many different kinds of data and methods. For the most recent example see Spielhagen et al. in Science Jan 28 2011:
“The Arctic is responding more rapidly to global warming than most other areas on our planet. Northward-flowing Atlantic Water is the major means of heat advection toward the Arctic and strongly affects the sea ice distribution. Records of its natural variability are critical for the understanding of feedback mechanisms and the future of the Arctic climate system, but continuous historical records reach back only ~150 years. Here, we present a multidecadal-scale record of ocean temperature variations during the past 2000 years, derived from marine sediments off Western Svalbard (79°N). We find that early–21st-century temperatures of Atlantic Water entering the Arctic Ocean are unprecedented over the past 2000 years and are presumably linked to the Arctic amplification of global warming. ”
When graphed, that looks much like a hockey stick — Fig. 3.
REPLY: The 64,000 dollar question: How does Mann/Briffa’s 12 trees from Yamal hold up when compared to the entire Schweingruber sample of 34?
The answer here and here.
– Anthony
I assume that more midges mean warmer temps and less midges mean cooler? Is that the train of thought? Over thousands of years midges don’t adapt/change? I thought some bugs mutated pretty rapidly. I think this part of the “research” is pretty skinny, but then I don’t know much about bugs. The midges we have here in WY seem to disappear when its windy and bother you when its calm. Not many around in the winter. Only see them near the water. Never see any in the dry flat lands or high in the mountains. Perhaps if they have been adapting then it has become even cooler over the period observed? Or maybe there were more birds and fish to eat them lately. Or how about changes in their environment other than temperature that caused less to hatch out/survive.
Probably a few too many variables involved here to make too much out of this. We are starting to sound like the AGW crowd, but then perhaps we need to fight fire with fire.
Paul Nurse:
Please stop this cherry picking!
Sir Paul Nurse – President of the Royal Society. I assume you are one and the same.
If so, I think your comment is a little pot and kettleish to say the very least. Your BBC2 Horizon effort this week was an utter disgrace to your profession. You should be ashamed of yourself for politicising science in the way you did. You referred to this blog as “denialist site”. You compared AGW skeptics to HIV deniers. You cherry picked 3 hours of discussion with James Dellingpole to create the editorial skew you required.
It was clear to me the only person in denial was you. Your efforts will embarrass the Royal Society in the coming years. You are a disgrace to you profession and your post.
There is evidence in the sunspot drawings & images that each Grand Minimum is capable of displaying different behavior.
Therefore, it is imperitive to current civilization to have a sober assessment of how closely the present Grand Minimum is driving the climate.
Is it a Lion or a Lamb?
Jim G says:
January 29, 2011 at 8:35 am
I assume that more midges mean warmer temps and less midges mean cooler?
——————-
The reconstruction isn’t based on abundance on midges, but on the relative proportions of different species. More midge remains from cold demanding species indicate cooler conditions, more remains from warm demanding species indicates warm conditions. The method is good when there are large temperature shifts (eg at the Younger Dryas-Holocene transition), it is less reliable when the temperature changes are relatively small.
I would so be going into caves and studying bat guano layers. And I know the damned stuff layers. It layered up in my attic. Midge population variation will affect bat population variation. Are there seasonal bats in our attic?
Anthony writes,
“OK let’s say the 193′s dust bowl warm spike (that it does catch) doesn’t matter either. That still leaves the question of how does the previous episodes of warmth happen without all our “modern” CO2.”
Wait, your “OK” there jumps past the fact that your lead paragraph for this post is simply false. The Clegg et al. paper does not demonstrate “that modern global warming is significantly less than the global warming experienced in the higher latitudes,” and the authors are clear as can be in explaining why not. Can you admit that mistake, before we change the subject?
REPLY: Refresh, I think you caught the comment in mid edit. I await your reply about Mann and 1960’s too, which suffers from the same problem you point out. – A
To Jim D (8:24 am), who says:
“On the other hand there is this new Science paper by Spielhagen et al. also linked from RC
http://climateprogress.org/2011/01/27/science-temperatures-atlantic-water-arctic-unprecedented-2000-years-linked-to-arctic-amplification-of-global-warming/
Basically the hockey stick is revived for the North Atlantic.”
Jim, I don’t have any reason to doubt the findings of the study showing that the Fram Strait has warmer waters than any time in the last 2,000 years. As with all new studies, including the one that is the subject of this particular post, it will need verification, but it may well end up being correct. We would also need to know if this is mostly a local effect, should it be verified.
A broader point remains, though: if we really are heading toward another ice ago, as this study and the Greenland ice core studies suggest (the Greenland ice cores showed that Greenland was substantially warmer around 6 to 8 thousand years ago than today, and follows the downward temperature trend with peaks around the RWP and MWP, as also found in this midge study), then is it harmful to have a warming trend to counter the downward temperature trend in the last 6,000 years or so?
We know from another journal article posted in WUWT a couple of months ago that the Arctic was substantially ice free in the summers, from about 6 to 8 thousand years ago — because researchers found deposition patterns on the coast that suggested large waves were regularly pounding the pebbles on the coast, leaving distinctive patterns that could only be made by waves. So the Arctic was substantially ice free in the warmest part of these summers, indicating a much warmer Arctic, in line with this midge study (and polar bears survived as well).
Again, I’m not on that bandwagon that says, we need to warm the earth to keep us out of another ice age. But we need paleoclimatologists to take this question seriously. When I look at these records which show so much more warmth about 6 yo 8 thousand years ago in the Arctic, it gives me pause about worrying too much about warming we see today. And if the Arctic was substantially ice free in parts of the summer for up to 2,000 years (6 to 8 thousand years ago), is it really a problem to have warm water from the Fram Strait be the specific mechanism for less Arctic sea ice?
Anthony will get on my case for suggesting that the Arctic sea ice might really be in a decline. Maybe things will reverse this coming decade, but to me the question isn’t whether there will be less Arctic sea ice going forward, it is whether such an eventuality is a disaster that needs costly and drastic action.