Skip to comments.New paleo reconstruction shows warmer periods in Alaska over the past 3000 years
Posted on 01/29/2011 6:52:36 AM PST by Ernest_at_the_Beach
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 demonstrate 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
Heres 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
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, 18001300, 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.
Heres 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 Soons website at Harvard here (PDF)
Hey, Sarah, come here willya'~ did you see what these guys did?
We who believe the Scriptures know that the earth was warm before the Noahidic flood worldwide and how the Lord God of Israel changed the post flood world into the four seasons we have now. Note verse 22 “While the earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease”
1 And God remembered Noah, and every living thing, and all the cattle that was with him in the ark: and God made a wind to pass over the earth, and the waters asswaged ; 2 The fountains also of the deep and the windows of heaven were stopped , and the rain from heaven was restrained ; 3 And the waters returned from off the earth continually : and after the end of the hundred and fifty days the waters were abated . 4 And the ark rested in the seventh month, on the seventeenth day of the month, upon the mountains of Ararat. 5 And the waters decreased continually until the tenth month: in the tenth month, on the first day of the month, were the tops of the mountains seen . 6 And it came to pass at the end of forty days, that Noah opened the window of the ark which he had made : 7 And he sent forth a raven, which went forth to and fro , until the waters were dried up from off the earth. 8 Also he sent forth a dove from him, to see if the waters were abated from off the face of the ground; 9 But the dove found no rest for the sole of her foot, and she returned unto him into the ark, for the waters were on the face of the whole earth: then he put forth his hand, and took her , and pulled her in unto him into the ark. 10 And he stayed yet other seven days; and again he sent forth the dove out of the ark; 11 And the dove came in to him in the evening ; and, lo, in her mouth was an olive leaf pluckt off: so Noah knew that the waters were abated from off the earth. 12 And he stayed yet other seven days; and sent forth the dove; which returned not again unto him any more. 13 And it came to pass in the six hundredth and first year, in the first month, the first day of the month, the waters were dried up from off the earth: and Noah removed the covering of the ark, and looked , and, behold, the face of the ground was dry . 14 And in the second month, on the seven and twentieth day of the month, was the earth dried . 15 And God spake unto Noah, saying , 16 Go forth of the ark, thou, and thy wife, and thy sons, and thy sons’ wives with thee. 17 Bring forth with thee every living thing that is with thee, of all flesh, both of fowl, and of cattle, and of every creeping thing that creepeth upon the earth; that they may breed abundantly in the earth, and be fruitful , and multiply upon the earth. 18 And Noah went forth , and his sons, and his wife, and his sons’ wives with him: 19 Every beast, every creeping thing, and every fowl, and whatsoever creepeth upon the earth, after their kinds, went forth out of the ark. 20 And Noah builded an altar unto the LORD; and took of every clean beast, and of every clean fowl, and offered burnt offerings on the altar. 21 And the LORD smelled a sweet savour; and the LORD said in his heart, I will not again curse the ground any more for man’s sake; for the imagination of man’s heart is evil from his youth; neither will I again smite any more every thing living, as I have done . 22 While the earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease
A solar clock and thermostat
It has seemed to me that there must have been dramatic warming in tundra areas all over the northern hemisphere followed by an abrupt chill. Otherwise how could it be that mammoths that are found complete with all soft tissue and stomach contents preserved sunken into the tundra?
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It’s not cars at all, it’a animals, 2 legged and 4 legged that are farting that caused globla warming!
This is a good thing. We actually need freezing if we’re going to drill up there. Rigs don’t set real well on mush!
Malawi is determined to mould responsible and disciplined citizens with a law banning the breaking of wind.
The Local Courts Bill of 2010 is set to be presented before a forthcoming parliamentary session by Justice Minister George Chaponda.
The legislation also targets ne'er-do-wells "disturbing religious assemblies", "trespassing on burial places", "insulting the modesty of a woman" or "challenging to fight a duel", as well as those who pass the time by pretending to be a fortune teller...
This study illustrates what often appears in scientific journals. It is a serious study of limited scope that presents data and findings in a unbiased fashion. The study shows that during the recent Quaternary period, temperatures at Moose Lake have risen and fallen in general correlation with recognized climate changes.
Once the popular science press (read: global warming cultists) gets their hands on this paper, they will report it to represent clear and undeniable evidence of anthropogenic global warming. Evil mankind is causing the temperatures at Moose Lake to skyrocket. All nonsense, of course, but these people are on a political crusade to destroy free market based capitalism and replace it with big government socialism. Deception and hyperbole in support of their one world vision is not only permitted, but encouraged.
Definitely, Bush/Cheney’s and Free Republic’s fault.
Someone ought to show NASA’s Hansen this article in counter to his “global warming BS”
Yet another interesting research article that provides evidence of natural warming/cooling cycles. The congress has so many good pieces of information they can go after the EPA with to stop the carbon trading tax schemes.
Good suggestion, but Hansen is a fanatic. Nothing will change his mind.
Careful what you ask for. I have a feeling that one, two and three mile thick ice sheets might complicate drilling for gas and oil.
That may very well be true, but right now, they can’t leave tracks in the tundra. That might upset the polar bears.
Crime in progress!
(1) With respect to the value of the Moose Lake record for assessing global warming:
As the name implies, global warming refers to an increase in the heat budget of the entire planet; the global heat budget is affected primarily by radiative controls, including (but not limited to) solar activity and orbital variations that alter how much energy Earth receives, and albedo and greenhouse gas concentration changes that alter rates of energy loss to space. Changes to the global heat budget can only be assessed by hemispheric or ideally global composites of temperature time series. The original Mann et al. publication was a pioneering example of this; additional global composite records have since become available.
Local atmospheric conditions are by far the most important controls on temperature trends at an individual site. Recent mean annual temperature rises in Alaska for instance have been attributed to changes in an atmospheric mode known as the North Pacific Index (NPI), for example. Better-known examples in other regions of the globe are the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). However, changes to the globes heat budget can significantly alter the frequency or amplitude of these atmospheric circulation patterns.
Recent warming in Alaska, while occurring throughout all months, is dominated by warming in the winter months. Winter is also the season with the strongest atmospheric patterns in each hemisphere due to the intense heat gradient between the tropics and the polar winter. Summer temperatures in Alaska are predominantly governed by cloud radiative forcing today. Comparing modern warming estimates of mean annual temperature (especially when referring to global trends) with the midge data which only capture mid-summer conditions is a bit like comparing apples and oranges.
As a side-note: The fact that warming predominately occurs in winter in Alaska is not trivial at these high latitudes, as winter conditions play a large role in influencing permafrost temperatures in summer, and hence can play a role in the development of a thermokarst landscape with potential positive greenhouse gas feedbacks.
(2) A comment on paleotemperature inferences:
Measuring prehistoric temperatures is crucial to gain a context for recent changes, and also to identify natural variations and perhaps even drivers of natural climate variations that play a role on longer timescales. However, it is a bit like measuring with a noisy thermometer. In this case, midge species differ in their temperature preferences, and multivariate analyses show that summer temperature is one of the dominant factors that explains the geographic distribution of different species of midge larvae. These relationships can be used to get an estimate of the average summer temperature at the time a sediment interval was deposited by identifying its larval midge remains. As might be expected, the precision of that estimate is far lower than reading a temperature value from a thermometer. Additionally, midges are biological organisms that respond to other environmental controls. Water depth, pH, cation concentrations, and nutrient status of lakes are a few examples. A good comparison with instrumental data is an encouraging sign that midges at a particular site are reliable indicators of temperature; other, multivariate techniques can also be used to try to identify periods during which the midge assemblages may have been affected by environmental factors other than summer temperature. However, it is important to keep this caveat in mind it is one of the principle reasons why replication of such studies is crucial. The second paragraph of the papers section 4.4 deals with such a possible caveat. The shift to on average higher temperatures between 4000 and 5000 years ago could have been influenced by low lake levels that were indicated by other lines of evidence. Other factors may have contributed during other periods but left no sign in the sediment. The more records that become available in the same region that point to shared temporal trends, the higher the confidence that the patterns represent regional controls including temperature, rather than lake or watershed-limited controls, such as changes to the pH or cation composition of the lakes water.
Guess I need to go back and read thru the article...might have some comments tomorrow.
Shutting down for the night here.