The oldest Antarctic ice core – finding a 1.5 million-year record of Earth’s climate

from environmentalresearchweb, November 6, 2013

How far into the past can ice-core records go? Scientists have now identified regions in Antarctica they say could store information about Earth’s climate and greenhouse gases extending as far back as 1.5 million years, almost twice as old as the oldest ice core drilled to date. The results are published today in Climate of the Past, an open access journal of the European Geosciences Union (EGU).

By studying the past climate, scientists can understand better how temperature responds to changes in greenhouse-gas concentrations in the atmosphere. This, in turn, allows them to make better predictions about how climate will change in the future.

“Ice cores contain little air bubbles and, thus, represent the only direct archive of the composition of the past atmosphere,” says Hubertus Fischer, an experimental climate physics professor at the University of Bern in Switzerland and lead author of the study. A 3.2-km-long ice core drilled almost a decade ago at Dome Concordia (Dome C) in Antarctica revealed 800,000 years of climate history, showing that greenhouse gases and temperature have mostly moved in lockstep. Now, an international team of scientists wants to know what happened before that.

At the root of their quest is a climate transition that marine-sediment studies reveal happened some 1.2 million years to 900,000 years ago. “The Mid Pleistocene Transition is a most important and enigmatic time interval in the more recent climate history of our planet,” says Fischer. The Earth’s climate naturally varies between times of warming and periods of extreme cooling (ice ages) over thousands of years. Before the transition, the period of variation was about 41 thousand years while afterwards it became 100 thousand years. “The reason for this change is not known.”

Climate scientists suspect greenhouse gases played a role in forcing this transition, but they need to drill into the ice to confirm their suspicions. “The information on greenhouse-gas concentrations at that time can only be gained from an Antarctic ice core covering the last 1.5 million years. Such an ice core does not exist yet, but ice of that age should be in principle hidden in the Antarctic ice sheet.”

As snow falls and settles on the surface of an ice sheet, it is compacted by the weight of new snow falling on top of it and is transformed into solid glacier ice over thousands of years. The weight of the upper layers of the ice sheet causes the deep ice to spread, causing the annual ice layers to become thinner and thinner with depth. This produces very old ice at depths close to the bedrock.

However, drilling deeper to collect a longer ice core does not necessarily mean finding a core that extends further into the past. “If the ice thickness is too high the old ice at the bottom is getting so warm by geothermal heating that it is melted away,” Fischer explains. “This is what happens at Dome C and limits its age to 800,000 years.”

To complicate matters further, horizontal movements of the ice above the bedrock can disturb the bottommost ice, causing its annual layers to mix up.

“To constrain the possible locations where such 1.5 million-year old – and in terms of its layering undisturbed – ice could be found in Antarctica, we compiled the available data on climate and ice conditions in the Antarctic and used a simple ice and heat flow model to locate larger areas where such old ice may exist,” explains co-author Eric Wolff of the British Antarctic Survey, now at the University of Cambridge.

The team concluded that 1.5 million-year old ice should still exist at the bottom of East Antarctica in regions close to the major Domes, the highest points on the ice sheet, and near the South Pole, as described in the new Climate of the Past study. These results confirm those of another study, also recently published in Climate of the Past.

Crucially, they also found that an ice core extending that far into the past should be between 2.4 and 3 km long, shorter than the 800,000-year-old core drilled in the previous expedition.

The next step is to survey the identified drill sites to measure the ice thickness and temperature at the bottom of the ice sheet before selecting a final drill location.

“A deep drilling project in Antarctica could commence within the next 3–5 years,” Fischer states. “This time would also be needed to plan the drilling logistically and create the funding for such an exciting large-scale international research project, which would cost around 50 million euros.”

Source: European Geosciences Union

http://environmentalresearchweb.org/cws/article/yournews/55225

"History of sea ice in the Arctic" by Leonid Polyak et al., Quartn. Sci. Rev., 29 (2010) doi:10.1016/j.quascirev.2010.02.010

Quarternary Science Reviews, 29 (2010) 1757–1778; doi:10.1016/j.quascirev.2010.02.010

History of sea ice in the Arctic


Leonid Polyak*, Richard B. Alley, John T. Andrews, Julie Brigham-Grette, Thomas M. Cronin, Dennis A. Darby, Arthur S. Dyke, Joan J. Fitzpatrick, Svend Funder, Marika Holland, Anne E. Jennings, Gifford H. Miller, Matt O’Regan, James Savelle, Mark Serreze, Kristen St. John, James W. C. White and Eric Wolff

Abstract

Arctic sea-ice extent and volume are declining rapidly. Several studies project that the Arctic Ocean may  become seasonally ice-free by the year 2040 or even earlier. Putting this into perspective requires information on the history of Arctic sea-ice conditions through the geologic past. This information can be provided by proxy records from the Arctic Ocean floor and from the surrounding coasts. Although existing records are far from complete, they indicate that sea ice became a feature of the Arctic by 47 Ma, following a pronounced decline in atmospheric pCO2 after the Paleocene–Eocene Thermal Optimum, and consistently covered at least part of the Arctic Ocean for no less than the last 13–14 million years. Ice was apparently most wide-spread during the last 2–3 million years, in accordance with Earth’s overall cooler climate. Nevertheless, episodes of considerably reduced sea ice or even seasonally ice-free conditions occurred during warmer  periods linked to orbital variations. The last low-ice event related to orbital forcing (high insolation) was in the early Holocene, after which the northern high latitudes cooled overall, with some superimposed shorter-term (multidecadal to millennial-scale) and lower-magnitude variability. The current reduction in Arctic ice cover started in the late 19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities.

Readers, for a discussion of the proxy records and the limitations of the various sediment cores from the Arctic Ocean and its margins, go to the link below and page 4.

Full, open-access paper at this link:  http://bprc.osu.edu/geo/publications/polyak_etal_seaice_QSR_10.pdf

Greenland ice may exaggerate magnitude of 13,000-year-old deep freeze (Younger Dryas)

Greenland ice may exaggerate magnitude of 13,000-year-old deep freeze

Ice samples pulled from nearly a mile below the surface of Greenland glaciers have long served as a historical thermometer, adding temperature data to studies of the local conditions up to the Northern Hemisphere's climate.

But the method – comparing the ratio of oxygen isotopes buried as snow fell over millennia – may not be such a straightforward indicator of air temperature.

"We don't believe the ice cores can be interpreted purely as a signal of temperature," says Anders Carlson, a University of Wisconsin–Madison geosciences professor. "You have to consider where the precipitation that formed the ice came from."

According to a study published today by the Proceedings of the National Academy of Sciences, the Greenland ice core drifts notably from other records of Northern Hemisphere temperatures during the Younger Dryas, a period beginning nearly 13,000 years ago of cooling so abrupt it's believed to be unmatched since.

Such periods of speedy cooling and warming are of special interest to climate scientists, who are teasing out the mechanisms of high-speed change to better understand and predict the changes occurring in our own time.

In the case of the Younger Dryas, average temperatures – based on the Greenland ice – plummeted as much as 15 degrees Celsius in a few centuries, and then shot back up nearly as much (over just decades) about 1,000 years later.

"In terms of temperature during the Younger Dryas, the only thing that looks like Greenland ice cores are Greenland ice cores," Carlson says. "They are supposed to be iconic for the Northern Hemisphere, but we have four other records that do not agree with the Greenland ice cores for that time. That abrupt cooling is there, just not to the same degree."

Working with UW–Madison climatologist Zhengyu Liu, collaborators at the National Center for Atmospheric Research and others, Carlson found their computer climate model breaking down on the Younger Dryas.

While it could reliably recreate temperatures in the Oldest Dryas – a similar cooling period about 18,000 years ago – they just couldn't find a lever in the model that would simulate a Younger Dryas that matched the Greenland ice cores.

"You can totally turn off ocean circulation, have Arctic sea ice advance all the way across the North Atlantic, and you still will have a warmer climate during the Younger Dryas than the Oldest Dryas because of the carbon dioxide," Carlson says.

By the time the Younger Dryas rolled around, there was more carbon dioxide in the air – about 50 parts per million more. The warming effects of that much CO₂ overwhelmed the rest of the conditions that make the Oldest and Younger Dryas so alike, and demonstrates a heightened sensitivity for Arctic temperatures to rising greenhouse gases in the atmosphere.

The researchers zeroed in on the Northern Hemisphere's temperature outlier, Greenland ice cores, and found that the conversion of oxygen isotope ratio to temperature typically used on the ice cores did not account for the sort of crash climate change occurring during the Younger Dryas. It assumes prevailing winds and jet streams and storm tracks are providing the moisture for Greenland precipitation from the Atlantic Ocean.

"The Laurentide ice sheet, which covered much of North America down into the northern United States, is getting smaller as the Younger Dryas approaches," Carlson says. "That's like taking out a mountain of ice three kilometers high. As that melts, it allows more Pacific Ocean moisture to cross the continent and hit the Greenland ice sheet."

The two oceans have distinctly different ratios of oxygen isotopes, allowing for a different isotope ratio where the water falls as snow.

"We ran an oxygen isotope-enabled atmosphere model, so we could simulate what these ice cores are actually recording, and it can match the actual oxygen isotopes in the ice core even though the temperature doesn't cool as much," Carlson says. "That, to us, means the source of precipitation has changed in Greenland across the last deglatiation. And therefore that the strict interpretation of this iconic record as purely temperature of snowfall above this ice sheet is wrong."

By the study's findings, Greenland temperatures may not have cooled as significantly as climate headed into the Younger Dryas relative to the Oldest Dryas, because of the rise in atmospheric carbon dioxide that had occurred since the Oldest Dryas.

"You can say at the end of the Younger Dryas it warmed 10, plus or minus five, degrees Celsius. But what happened on this pathway into the event, you can't see," Carlson says.

It's a fresh reminder from an ancient ice core that climate science is full of nuance, according to Carlson.

"Abrupt climate changes have happened, but they come with complex shifts in the way climate inputs like moisture moved around," he says. "You can't take one difference and interpret it solely as changes in temperature, and that's what we're seeing here in the Greenland ice cores."

The National Science Foundation and Department of Energy funded the research.

http://environmentalresearchweb.org/cws/article/yournews/50095

Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation, Nature 484, Jeremy D. Shakun et al.

Nature 484, 49-54 (5 April 2012); doi:10.1038/nature10915

Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation

• Jeremy D. Shakun,
• Peter U. Clark,
• Feng He,
• Shaun A. Marcott,
• Alan C. Mix,
• Zhengyu Liu,
• Bette Otto-Bliesner,
• Andreas Schmittner and
•  Edouard Bard

Abstract

The covariation of carbon dioxide (CO₂) concentration and temperature in Antarctic ice-core records suggests a close link between CO₂ and climate during the Pleistocene ice ages. The role and relative importance of CO₂ in producing these climate changes remains unclear, however, in part because the ice-core deuterium record reflects local rather than global temperature. Here we construct a record of global surface temperature from 80 proxy records and show that temperature is correlated with and generally lags CO₂ during the last (that is, the most recent) deglaciation. Differences between the respective temperature changes of the Northern Hemisphere and Southern Hemisphere parallel variations in the strength of the Atlantic meridional overturning circulation recorded in marine sediments. These observations, together with transient global climate model simulations, support the conclusion that an antiphased hemispheric temperature response to ocean circulation changes superimposed on globally in-phase warming driven by increasing CO₂ concentrations is an explanation for much of the temperature change at the end of the most recent ice age.

http://www.nature.com/nature/journal/v484/n7392/full/nature10915.html

V. Masson-Delmotte et al., Clim. Past (2011), A comparison of the present and last interglacial periods in six Antarctic ice cores

Climate of the Past, 7 (2011) 397-423; doi:10.5194/cp-7-397-2011. www.clim-past.net/7/397/2011/

A comparison of the present and last interglacial periods in six Antarctic ice cores

V. Masson-Delmotte¹, D. Buiron², A. Ekaykin³, M. Frezzotti⁴, H. Gallée², J. Jouzel¹, G. Krinner², A. Landais¹, H. Motoyama⁵, H. Oerter⁶, K. Pol¹, D. Pollard⁷, C. Ritz², E. Schlosser⁸, L. C. Sime⁹, H. Sodemann¹⁰, B. Stenni¹¹, R. Uemura^1,12, and F. Vimeux^1,13
1Laboratoire des Sciences du Climat et de l'Environnemen, IPSL-CEA-CNRS-UVSQ, UMR 8212, Gif-sur-Yvette, France
²CNRS and UJF, Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE, UMR 5183), Grenoble, France
³Arctic and Antarctic Research Institute, 38 Beringa St., 199397 St. Petersburg, Russia
⁴ENEA, Rome, Italy
⁵Research Organization of Information and Systems, National Institute of Polar Research, 10-3, Midoricho, Tachikawa, Tokyo, 190-8518, Japan
⁶Alfred Wegener Institute for Polar and Marine Research, Helmholtz Association, Bremerhaven, Germany
⁷Earth and Environmental System Institute, Pennsylvania State University, University Park, USA
⁸Institute of Meteorology and Geophysics, University of Innsbruck, Innsbruck, Austria
⁹British Antarctic Survey, Cambridge, UK
¹⁰Norwegian Institute for Air Research, NILU, Kjeller, Norway
¹¹Department of Geosciences, University of Trieste, Trieste, Italy
¹²Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan
¹³Institut de Recherche pour le Développement, IRD, Laboratoire HydroSciences Montpellier, HSM, UMR 5569, CNRS-IRD-UM1-UM2, Montpellier, France
Abstract

We compare the present and last interglacial periods as recorded in Antarctic water stable isotope records now available at various temporal resolutions from six East Antarctic ice cores: Vostok, Taylor Dome, EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML), Dome Fuji and the recent TALDICE ice core from Talos Dome. We first review the different modern site characteristics in terms of ice flow, meteorological conditions, precipitation intermittency and moisture origin, as depicted by meteorological data, atmospheric reanalyses and Lagrangian moisture source diagnostics. These different factors can indeed alter the relationships between temperature and water stable isotopes. Using five records with sufficient resolution on the EDC3 age scale, common features are quantified through principal component analyses. Consistent with instrumental records and atmospheric model results, the ice core data depict rather coherent and homogenous patterns in East Antarctica during the last two interglacials. Across the East Antarctic plateau, regional differences, with respect to the common East Antarctic signal, appear to have similar patterns during the current and last interglacials. We identify two abrupt shifts in isotopic records during the glacial inception at TALDICE and EDML, likely caused by regional sea ice expansion. These regional differences are discussed in terms of moisture origin and in terms of past changes in local elevation histories, which are compared to ice sheet model results. Our results suggest that elevation changes may contribute significantly to inter-site differences. These elevation changes may be underestimated by current ice sheet models.

© Author(s) 2011. This work is distributed under the Creative Commons Attribution 3.0 License.
Final Revised Paper (PDF, 4492 KB)   Discussion Paper (CPD)   

Citation: Masson-Delmotte, V., Buiron, D., Ekaykin, A., Frezzotti, M., Gallée, H., Jouzel, J., Krinner, G., Landais, A., Motoyama, H., Oerter, H., Pol, K., Pollard, D., Ritz, C., Schlosser, E., Sime, L. C., Sodemann, H., Stenni, B., Uemura, R., and Vimeux, F.: A comparison of the present and last interglacial periods in six Antarctic ice cores, Clim. Past, 7, 397-423, doi:10.5194/cp-7-397-2011, 2011.


http://www.clim-past.net/7/397/2011/cp-7-397-2011.html

Rob Honeycutt, Skeptical Science: "The name is Bond...Gerard Bond" -- A Pervasive Millennial-Scale Cycle in North Atlantic Holocene and Glacial Climates

The name is Bond...Gerard Bond

by Rob Honeycutt, Skeptical Science, March 12, 2011

One of the main climate skeptic claims when presenting the Greenland Ice Sheet Project 2 (GISP2) record is that climate change during the Holocene is normal, that there is nothing new about the warming we see today. This is not a claim that is substantiated by the full body of research. We're going to take out a "license to kill" this particular skeptic meme.

The name is Bond...Gerard Bond.  

Specifically, the Bond et al. (1997) article entitled, A Pervasive Millennial-Scale Cycle in North Atlantic Holocene and Glacial Climates. Okay, this Bond doesn't quite have Ian Fleming's knack for a catchy titles, but we'll work with it. 

Many of you may be familiar with Dansgaard-Oeschger (D-O) events. These are the rapid climate change events we see in the ice core data during glacial periods. They are easily recognizable in the GISP2 core by rapid warming followed by slower cooling, following an aproximately 1,470-year cycle. D-O events are also notable in the climate record as being a redistribution within the climate system because they are also found in Antarctic cores with a corresponding but reverse signal called an "antiphase," i.e., offsetting warming and cooling between the Arctic and Antarctic. This is not the planet heating up suddenly and then cooling off. It is the planet rearranging how heat is distributed within the overall climate system. This is often referred to as a "bipolar seesaw."

Shaken, not stirred.... Ice-Rafted Debris

Bond et al. take a look at the Holocene and identify a similar, but lesser, bipolar seesaw effect at work. The work is primarily done by looking at ice-rafted debris (IRD) in sea bottom cores around the North Atlantic. During warming events, more ice calves off glaciers, and with that ice comes debris that is distributed on the sea floor as the ice melts. Bond et al. looked at the distance of flow patterns of this debris as it is distributed on the sea floor. These are referred to as "pulse" events in sea bottom cores, and the timing of these deposits are then correlated with warming events in the GISP2 ice core record.

Figure 1.  Core locations and NA currents from Bond et al. (1997).

There are 8 primary Bond events at 1,400, 2,800, 4,200, 5,900, 8,100, 9,400, 10,300, and 11,100 years ago. Here we are going to stick with just the 6 events that fall within the Holocene.

Figure 2.  Six Bond events identified through ice-rafted debris (click for larger image).

The most dramatic of these is the "8.2 kyr" event, or Bond event 5. There is a reverse event which is quite dramatic in the Vostok ice core. If we further compare the GISP2 and Vostok temperature records, we can see a very large number of antiphased events, though these are not specifically identified as Bond events.

Figure 3.  Numerous other antiphased events in the ice core records (click for larger image).

There is still much that is not well understood about what drives both D-O and Bond events. There is still a great deal of debate on whether they are actually cyclical or coincidental, and what forcing might be driving them. Recent research, such as that of Maslin (2009), is beginning to better clarify the bipolar nature of the Holocene.

Why yes, Miss Moneypenny...

Those of you who are observant will note several important events these two records point out. It is notable to see that the Medieval Warm Period around 800–1,000 years BP is quite dramatic in the Greenland record but is not evident in the Antarctic record. There is also the so-called Roman Warm Period around 2,000 years BP that clearly has a reverse response in the Vostok core. 

When we start reconciling these records we find, yes, there are dramatic and rapid climate change events in the Holocene. Larger changes tend to occur in the high latitudes of the Northern Hemisphere, while the Southern Hemisphere remains more stable, with occasional redistributions of temperature from the north. We often see dramatic changes in temperature in a single location, but this doesn't represent change in the global climate as much as it represents a redistribution of temperature. 

Proxy Galore

What we learn from Bond events is that global climate was still dynamic during the Holocene, though profoundly less so than during glacial periods. Looking at any single proxy record of temperature (e.g., the GISP2 ice core) will only tell us about the climate of that particular location. Scientific understanding of global temperature in the past requires looking at a wide range of proxies.

What differs today is that we see nearly all records and indicators of temperature rising, whether they are glaciers melting, ice mass loss, patterns of animal migrations, ocean acidification, intensification of precipitation events, or many other lines of evidence. Today these are nearly all collectively pointing in only one direction. They are telling us unequivocally (per the language of the IPCC) that we are warming the entire planet... potentially with a "view to a kill."

http://www.skepticalscience.com/Bond-Gerard-Bond.html

Peter Sinclair: What the Ice Cores Tell Us, and How Deniers Like WUWT Distort it

Peter Sinclair: What the Ice Cores Tell Us, and How Deniers Like WUWT Distort It

Link:  http://www.youtube.com/watch?v=c90nab5i-TQ

Peter Sinclair: What the ice cores tell us

New Crock Video: What the Ice Cores Tell Us

February 2, 2011

Judging from comments I get on the YouTube site, many deniers apparently believe that not too long ago, Greenland was green.
Like, really green.


In fact, Wisconsin Senator Ron Johnson gave voice toTea Party science when he told an interviewer, “There’s a reason Greenland was called Greenland,” he said. “It was actually green at one point in time. And it’s been, since, it’s a whole lot whiter now.”

But to  find a greenland without glaciers and an ice sheet, you have to go back a little further in time.

65 million years ago, when reptiles swam and hunted there.

The more recent past was less idyllic.

Ice core data indicates the the greenland ice sheet is at least 400,000 years old.




While Greenland ice cores tell us much about the past, they are not the only ice cores available
For some 30 years, ice from tropical glaciers has also been examined by Scientists from the Byrd Polar research Center, at Ohio State university, who have packed heavy equipment up some of the highest mountains in the world to preserve a vanishing record.

Ellen Mosley Thompson, and her husband Lonnie Thompson, have been among theleading  pioneers in this heroic scientific effort - organizing and leading the transport, often by pack animals, of cutting edge scientific teams to some of the world’s most remote regions.

In December 2010, Ellen Mosley Thompson explained some of their key findings to the  American Geophysical Union. So, hard evidence from tropical ice cores and other records is  showing us empirically that the medieval period that climate deniers like to talk about  was indeed regionally warm, but not a global phenomenon, like today.

Climate deniers love to tell you that the science of global warming depends on abstractions and computer models, but the evidence for man caused warming in fact has been painstakingly built up by some of the hardest of of the hard sciences – the real, boots on the ground grunt work of courageous  and dedicated professionals – the spiritual heirs of bold viking explorers of the past.

The tiny colonies that survived in greenland during a brief, regional mild period must indeed have been tough and resourceful people, but not the thriving high culture of climate denier imagination.

More About Medieval Warming:

Link:  http://climatecrocks.com/2011/02/02/new-crock-video-what-the-ice-cores-tell-us/

TED.com: Lee Hotz reports on the WAIS Divide ice core drilling project

Antarctica from the Warmth of Your Own Home

from Climate Central, August 27, 2010

As you head into one of your last full weekends of the summer, we thought we would leave you with some Antarctic eye-candy.  Recently posted on TED.com is a presentation made by Wall Street Journal science journalist Lee Hotz. The video is less than 10 minutes long but is brimming with stunning visuals of an exploration site from Antarctica known as WAIS Divide, where researchers are drilling Antarctic ice cores to learn more about the history of earth’s climate.


The comments stream at the bottom of the video indicates that viewers were none too pleased that Hotz didn’t present more data. The truth of the matter is that – in addition to the fact that Hotz isn’t a scientist with the project – the data just doesn’t exist yet. As he emphasizes at the 1:48 min. mark, “what we don’t know is the exact, precise, immediate impact of these changes on natural climate patterns.” The entire focus of the project, which is still ongoing, is to find answers to how the climate has changed in the past, when such changes took place, and maybe even answers into the all important question of why?

Yes, it is unusual to tell people that scientists are seeking out information, rather than waiting to tell them once the scientists have figured it all out. But here Hotz so clearly explains why we need to study ice core data and how scientists actually conduct such work that the presentation is still meaningful.

"The ice of Antarctica is a calendar of climate change. It records the annual rise and fall of greenhouse gases and temperatures going back before the onset of the last ice ages" -- Lee Hotz

The project Hotz talks about in Antarctica also reminds us of the NEEM Project in Greenland that we’ve previously reported on in both blog and video formats. Though they are on opposite ends of the planet, the two ice core projects are expected to yield equally rich climate history data in the years to come.

Link:  http://climatecentral.org/breaking/blog/climate_in_context_august_27_2010

Dr Richard Alley puts paid to wmar's ridiculous industry-bought-and-paid-for pseudoscience on Dot Earth

Reality check on old ice, climate and CO2

by ANDREW C. REVKIN, February 8, 2010

Richard Alley’s name has been thrown around a bit by bloggers asserting that ice-core records from Greenland show  that carbon dioxide has scant, if any, influence on climate. Dr. Alley, a glaciologist and climate scientist at Penn State, is a longtime contributor to the Intergovernmental Panel on Climate Change, author of a nice history of ice and climate, “ The Two-Mile Time Machine,” and — as many Dot Earth readers are aware — a teacher with musical and terpsichorean talents (see the YouTube video below for his orbital dance explaining how ice-age cycles help show the amplifying power of greenhouse gases).

Apture™

There have been repeated references to his work here by skeptics of human-driven warming, most notably by “wmar.” Here’s an example (link to full comment is here):

The ice tells us about the past, and from Dr. Alley of the I.P.C.C., it is entirely clear that the carbon/temperature link is either a fallacy or negligible. Unlike the I.P.C.C. or any such pro AGW group, the ice cores have no emotions or agendas and simply are what they are … let’s have a look shall we?
WattsUpWithThat…

I sent a query to Dr. Alley about such interpretations of his work and the ice-core record and he sent a reply, the heart of which is pasted below. Where he refers to  GISP2, he’s describing a particular ice core extracted during what was called “Greenland Ice Sheet Project 2.”

First off, no single temperature record from anywhere can prove or disprove global warming, because the temperature is a local record, and one site is not the whole world. One of the lessons drawn from comparing Greenland to Antarctica and many other places is that some of the temperature changes (the ice-age cycling) are very widespread and shared among most records, but other of the temperature changes (sometimes called millennial, or abrupt, or Younger-Dryas-type) are antiphased between Greenland and the south, and still other temperature changes may be unrelated between different places (one anomalously cold year in Greenland does not tell you the temperature anomaly in Australia or Peru). After scientists have done the hard work of working out these relations, it is possible to use one ice-core record to represent broader regions IF you restrict consideration to the parts that are widely coherent, so it is O.K. to plot a smoothed version of an Antarctic temperature record against CO2 over long times and discuss the relation as if it is global, but a lot of background is required.

Second, although the central Greenland ice-core records may provide the best paleoclimatic temperature records available, multiple parameters confirm the strong temperature signal, and multiple cores confirm the widespread nature of the signal, the data still contain a lot of noise over short times (snowdrifts are real, among other things). An isotopic record from one site is not purely a temperature record at that site, so care is required to interpret the signal and not the noise. An extensive scientific literature exists on this topic, and I believe we are pretty good in the community at properly qualifying our statements to accord with the underlying scientific literature; the blogospheric misuses of the GISP2 isotopic data that I have seen are not doing so, and are making errors of interpretation as a result.

Thirdly, demonstration that there have been large climate changes in the past without humans in no way demonstrates that humans are not now responsible. Many people have died naturally but murder still exists; it is up to the police to learn whether a given mortality was natural or not, and up to climate science to learn what is causing ongoing changes (and we have good confidence that most of what is happening to climatic global average surface temperature is being caused by humanity now). Similarly, demonstration that life, and humans, survived warmer temperatures in the past in no way shows that warmer temperatures in the future are good for us. If you don’t care about humans and other things with us here, making a big change in climate might be an interesting experiment. Evolution does respond to climate change and produce novel results. I just happen to have a personal bias (shared, I believe, by the majority of the six-plus billion people on the planet) that we should ask what is best for humanity, and pursue that. An opinion, surely, and not purely scientific, but that’s my bias.

So, what do we get from GISP2? Alone, not an immense amount. With the other Greenland ice cores (which demonstrate that the GISP2 record is quite good and reproducible), and compared to additional records from elsewhere, an immense amount.

> More sunshine from orbital changes produces warming. The magnitude looks consistent with our understanding of the climate system.

> Some of the “wiggles” in temperature (such as the Little Ice Age signal) correlate with changes in solar output. The beryllium-10 record provides an imperfect but useful estimate of the past variations of solar output, after correction for effects of magnetic-field variation on beryllium-10 production. The resulting solar fluctuations have been small over the times of good climate records, with small climate response, as expected. Again, there is no solid evidence for any weirdness, special sensitivity of climate to the sun, or large solar variations, but instead a generally good match to expected behavior of the climate system. (I’m among those who have looked very hard to find weirdness, too.)

> Nothing else really weird appears in forcings of climate change. No major changes are found in space dust, which remains rare enough that it cannot have been very important. Large changes in cosmic rays are documented in response to magnetic-field variations (the Laschamp event of about 40,000 years ago is especially prominent) with no corresponding change in climate, so any cosmic-ray influence on the climate must be very small (a weak correlation can be obscured by noise; a strong control is almost always visible “by eye,” and clearly is absent). Volcanic eruptions and local climate response are recorded, and again appear consistent with expectations of climate science. There may be small but interesting time-variations in eruptions, but the record is almost entirely one of “noise”–if volcanoes could get organized they could be very important agents of climate change, but they aren’t organized. (The recent work of Huybers and Langmuir suggests that on ice-age time scales, the loading and unloading of the planet by ice growth/shrinkage and sea-level fall/rise may weakly organize the volcanoes, but not a lot, and with nothing interesting for our time.)

Climate is surely a lot of things. The data show that the sun’s variations have been small over the times we care about, the climate responds to variations in sunshine caused by orbital changes, but these are slow. CO2 matters a lot. Volcanoes make “noise.” With those in your pocket, you’re a long way to understanding changes in Earth’s climate—not done, but well on your way.

The abrupt-climate-change story remains interesting, though. Today, the salty north Atlantic waters sink before they freeze in the winter. The data indicate that at times in the past, the north Atlantic was fresher so the waters froze before they sank. The resulting wintertime cooling in the north Atlantic was rather severe, and the influences far from the north Atlantic included a general southward shift of the tropical circulations and drying of monsoonal and northern-tropical regions where billions now live. The IPCC gives >90% chance that the melting of Greenland’s ice and other changes in the future will not be fast enough to trigger such a discontinuity over the next century, but >90% is not necessarily 100%. The implications, that slowing down or stopping the melting may buy insurance against a rare but catastrophic outcome, are interesting.

So, using GISP2 data to argue against global warming is, well, stupid, or misguided, or misled, or something, but surely not scientifically sensible. And, using GISP2 data within the larger picture of climate science demonstrates that our scientific understanding is good, supports our expectation of global warming, but raises the small-chance-of-big-problem issue that in turn influences the discussion of optimal human response.

 Link:  http://dotearth.blogs.nytimes.com/2010/02/08/richard-alley-on-old-ice-climate-and-co2/

Valérie Masson-Delmotte, SCAR Lecture: “Climate Change: an Antarctic Perspective”

Dr Valérie Masson-Delmotte, from the Laboratoire de Modélisation du Climat et de l’Environnement, Gif-sur-Yvette, France gave the SCAR Lecture on “Climate Change: an Antarctic Perspective” 

The text of her talk and copies of the slides were provided as ATCM XXIX IP 76. [Readers, I believe this lecture was given in 2006, but the data is still true.]

The PowerPoint slides are available separately on the SCAR web site, at www.scar.org/communications/.

Dr Masson-Delmotte explained that ice cores provide unique climate archives containing information on past climate and environmental changes at local, regional and global scales. The isotopic composition of the water trapped as ice allows us to estimate the past temperature of the Antarctic region. The chemical composition of the ice also includes information on dust and aerosols transported by the atmosphere, which help us to understand the extent of droughts and volcanic activity on surrounding continents. Finally, air bubbles trapped in the ice enable us to determine the composition and abundance of greenhouse gases in the atmosphere through time. Comparing the data from the present with those from the past enables us to determine the impact of human activities on the composition of the atmosphere. Comparison with the past record, and knowledge of the way in which the Earth receives radiation over periods of thousands of years during its orbit around the sun, suggests that the Earth today is in a long “interglacial”, which should last a further 30,000 years before the descent into a new ice age. The data from air bubbles trapped in the ice show that the present levels of the greenhouse gases methane and CO2 are considerably higher than anything experienced in the atmosphere of the last 650,000 years. These increases are entirely due to human activities (intensive agriculture and massive use of fossil fuels). Temperature is also increasing. The rate of increase in temperature over the past 100 years has taken place 25 times faster than any natural changes over the past 650,000 years.

Link to page 7 of the pdf file (Annex H, page 497):  http://www.ats.aq/documents/atcm_fr_images/ATCM29_fr004_e.pdf

Greenland ice cores show us the Eemian Period

Drilling Back to the Future: Climate Clues from Ancient Ice on Greenland - Enhanced Transcript

• Published: November 13th, 2009, in Arctic & Greenland, Trends, Projections, Snow & Ice, Oceans & Coasts, Sea Level
• Originally broadcast on: October 19, 2009 on PBS's The NewsHour with with Jim Lehrer.

Ice cores show us the Eemian Period

1. 
   
   

   0:03

   Heidi Cullen: Far in the north of Greenland, a team of climate scientists from 14 nations, including the US, has just completed its first season of drilling a 1.6-mile core of solid ice.

   
   
   
   


2. 
   
   

   0:16

   JP Steffensen : What you see here is a piece of ice from the climate change between the last glacial and the present climate. It’s about 11,000 years old and it contains a lot of tiny little bubbles of the ancient atmosphere.

   
   
   
   


3. 
   
   

   0:28

   Heidi Cullen: JP Steffensen is the Field Operations Manager for the North Greenland Eemian Ice Drilling Project or NEEM. The project’s ultimate goal…to unlock the climate history trapped inside those tiny bubbles.

   
   
   
   


4. 
   
   

   0:42

   Jeff Severinghaus: The beautiful thing about an ice core is that it's got all of these different indicators: atmosphere composition, temperature, mean ocean temperature, dust. All these kinds of indicators on exactly the same time scale.

   
   
   
   


5. 
   
   

   0:56

   Heidi Cullen: Jeff Severinghaus, a scientist at the Scripps Institution of Oceanography, is working with NEEM scientists to reconstruct all those indicators in the hope of learning more about a period in climate history known as the Eemian.

   
   
   
   


6. 
   
   

   1:09

   Heidi Cullen: The Eemian Period started about 130,000 years ago, and we know it lasted about 15,000 years before the earth plunged back into an ice age.

   
   
   
   


7. 
   
   

   1:19

   Jeff Severinghaus: NEEM is really trying to get a record of the last time that the earth was warmer than today. So it’s an analog of what our future looks like under global warming.

   
   
   
   


8. 
   
   

   1:30

   Heidi Cullen: During the Eemian, temperatures were somewhere between 5 and 9 degrees Farenheit warmer than today…a scenario that climate models suggest could happen again by the end of the century if present trends continue.

   
   
   
   


9. 
   
   

   1:42

   Jeff Severinghaus: It’s a very realistic scenario for what we may experience in the next hundred to two hundred years.

   
   
   
   


10. 
    
    

    1:53

    Simon Shupbach: We are getting older and older with every meter that we melt; we are getting back to the future.

    
    
    
    


11. 
    
    

    1:58

    Heidi Cullen: Thirty feet below the surface in the huge trench carved from snow is where the ice ore research begins.

    
    
    
    


12. 
    
    

    2:05

    JP Steffensen : The newest thing that we have right now at NEEM that nobody else has tried is the very sophisticated analytical system. It’s called continuous flow analysis, where actually in the field you cut a slab of the ice core, a thin rod of ice following the length of the ice and you tilt that vertically and you melt it on the hot plate from one end and then as it melts you do the analysis, millimeter by millimeter.

    
    
    
    


13. 
    
    

    2:29

    Simon Shupbach: You can hear the bubbles coming out of the ice.

    
    
    
    


14. 
    
    

    2:34

    Heidi Cullen: The samples are also cut, bagged and boxed up, and then shipped to research centers around the world.

    
    
    
    


15. 
    
    

    2:44

    JP Steffensen : We call it the Post Office.

    
    
    
    


16. 
    
    

    2:47

    Heidi Cullen: The logistics of ice core drilling are far from simple.

    
    
    
    


17. 
    
    

    2:51

    JP Steffensen : It’s just complicated. And I hate complications. I like for things to run smoothly.

    
    
    
    

Life in Greenland

1. 
   
   

   2:56

   Heidi Cullen: The operation starts in the small town of Kangerlussuaq on Greenland’s west coast.

   
   
   
   


2. 
   
   

   3:01

   JP Steffensen : My first season was in 1980. So that’s 29 years ago. And that was a marriage for life.

   
   
   
   


3. 
   
   

   3:10

   Heidi Cullen: Keeping the operation running smoothly is his wife and fellow scientist, Dorthe Dahl-Jensen, NEEM’s project leader.

   
   
   
   


4. 
   
   

   3:18

   Dorthe Dahl-Jensen: I work mostly as coordinator of the project, and I need to get the drill teams, and the scientists, and the logistics people and the airplanes to come.

   
   
   
   


5. 
   
   

   3:25

   Heidi Cullen: The airplanes come courtesy of the 109th Airlift Wing of the New York Air Force National Guard…and pilots like George Alston.

   
   
   
   


6. 
   
   

   3:35

   George Alston: Well, we’re the only unit in the world that flies the specialized LC-130 aircraft, a C-130 on skis, which allows us to support the scientific efforts and take these large airplanes and land them on skis.

   
   
   
   


7. 
   
   

   3:47

   Heidi Cullen: But getting to the ice drilling camp is just part of the challenge.

   
   
   
   


8. 
   
   

   3:52

   Vasilii Petrenko: It's always light, so when you first get here it may be a little hard to sleep. It takes a couple of nights to get used to it, but then you get so tired from work and from not sleeping nights before, that it no longer becomes a problem.

   
   
   
   


9. 
   
   

   4:04

   Heidi Cullen: Vasilii Petrenko is a scientist at the University of Colorado.

   
   
   
   


10. 
    
    

    4:08

    Vasilii Petrenko: It’s a very simple life. It’s kind of like a frontier outpost. We sleep mostly in those red structures that you see behind me; they are called weather ports.

    
    
    
    


11. 
    
    

    4:19

    Heidi Cullen: While the NEEM field camp may look like a frontier outpost on the surface, Petrenko and others are engaged in very sophisticated scientific research underground.

    
    
    
    

What NEEM Is Teaching Us

1. 
   
   

   4:28

   Vasilii Petrenko: One of the things that we see in the ice cores is a strong correlation between carbon dioxide levels and temperatures. So at times of warm temperatures, carbon dioxide is high, at times of cold temperatures; carbon dioxide is low which reinforces what science has been showing recently, that carbon dioxide does cause warming.

   
   
   
   


2. 
   
   

   4:48

   Heidi Cullen: And that warming leads to melting. The Greenland ice sheet contains enough ice to raise global sea level by 23 feet - a worst-case scenario associated with global warming.

   
   
   
   


3. 
   
   

   5:00

   Heidi Cullen: Satellite data from the NASA Grace mission show that Greenland’s reservoir of ice has plummeted in recent years. About 340 billion tons of ice melt in 2007 alone – about the same as San Francisco Bay draining completely every week for a year.

   
   
   
   


4. 
   
   

   5:17

   Heidi Cullen: Scientists hope this new ice core will tell them how much of Greenland’s ice melted during the Eemian Period – when global sea level was 13 to 20 feet higher, a finding that could be crucial in determining how much and how quickly sea level could rise over the next several centuries.

   
   
   
   


5. 
   
   

   5:33

   Dorthe Dahl-Jensen: We know from all the other ice cores that we have drilled that we find ice from the Eemian period in the ice cores. Of course this immediately tells us that even though it was warmer in Greenland, it wasn’t warm enough for the whole Greenland ice sheet to disintegrate. And that’s something that is debated a lot; how much warming we would need in the future before the Greenland ice sheet would totally disappear, before we go beyond the tipping point.

   
   
   
   


6. 
   
   

   5:56

   Heidi Cullen: Now that this drilling season has come to an end, the scientists are heading home, working to unlock the climate history trapped inside those tiny, but telling, bubbles.

    Link:   http://www.climatecentral.org/science/transcript/drilling_back_to_the_future_climate_clues_from_ancient_ice_on_greenland

   
   
   
   

Ice core drilling at Neem, Greenland, back to 150,000 years ago

Please take careful note of what the scientist says about temperatures rising about 20 °F in just a couple of years -- she may be referring to the Younger Dryas -- at about minute 1:50.

Visit msnbc.com for breaking news, world news, and news about the economy

Link:  http://www.msnbc.msn.com/id/21134540/vp/34239910#34050658

J. P. Steffensen et al., Science 2008, High-resolution Greenland ice core data show abrupt climate change happens in few years

Science, published online June 19, 2008

High-resolution Greenland ice core data show abrupt climate change happens in few years

J. P. Steffensen et al.


Abstract

The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, are investigated in high temporal resolution from the Greenland NGRIP ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switches mode within 1 to 3 years over these transitions and initiates a more gradual change (50 years) of the Greenland air temperature as recorded by water stable isotopes. The onsets of both abrupt Greenland warmings are slightly preceded by decreasing Greenland dust deposition, reflecting wetting of Asian deserts. A northern shift of the ITCZ could be the trigger of these abrupt shifts of northern hemisphere atmospheric circulation resulting in 2 to 4K changes in Greenland moisture source temperature from one year to the next.

Link to abstract:  http://www.sciencemag.org/cgi/content/abstract/1157707v1

Greenland Ice Sheet’s elevation change in winter and atmospheric circulation

Nuuk Climate Days 2009 -- Changes of the Greenland Cryosphere Workshop & The Arctic Freshwater Budget International Symposium, Nuuk, Greenland, 25-27 August 2009

Primary author: CHEN, Linling (Nansen-Zhu International research center/Institute of Atmospheric Physics,
Chinese Academy of Sciences), lin-ling.chen@nersc.no ; Co-authors: JOHANNESSEN, Ola M. (Nansen Environmental and Remote Sensing Center); WANG, Huijun (Nansen-Zhu International research center/Institute of Atmospheric Physics, Chinese Academy of Sciences);  KHVOROSTOVSKY, Kirill (Nansen Environmental and Remote Sensing Center)

Abstract ID: F4
 
Greenland Ice Sheet’s elevation change in winter and atmospheric circulation

Data from ERS-1, ERS-2 and Envisat Satellites are analyzed to identify the relationship between winter elevation variations of Greenland ice sheet and sea level pressure during 1993-2007. It is found that the North Pacific oscillation and the North Atlantic oscillation, the two major teleconnection patterns of surface pressure fields in North Hemisphere, both have significant impacts on the Greenland ice sheet winter elevation change by influencing accumulation. In addition, we are evaluating modeled precipitation data over Greenland based on comparison with accumulation data from all available ice core records and meteorological station, in order to better understand how the atmospheric circulation impact the Greenland Ice Sheet’s Elevation.