Again, this isn't meant to prove anything; but just to show what is going on in the field.
Sorry some of the math/chemistry symbols didn't copy well....googled: "ice core data" reliability
Reconstruction of atmospheric CO from ice-core data and the deep ...records to ice-core data, by multiple regression, for the. purpose of backward extrapolation. ..... providing a sense of the reliability of sea-level recon- ...
www.springerlink.com/index/BNWHVW81PQKD5DXL.pdf http://herkules.oulu.fi/isbn9514281853/isbn9514281853.pdfKekonen, Teija, Environmental information from the Svalbard ice core for the past
800 years
Faculty of Science, Department of Chemistry, University of Oulu, P.O.Box 3000, FI-90014
University of Oulu, Finland
Acta Univ. Oul. A 469, 2006
Oulu, Finland
Abstract
Major water soluble ions (Cl-, NO3-, SO4 2-, CH3SO3-, Na+, K+, NH4+, Mg2+, Ca2+) were determined and the results interpreted from a 121 m long ice core drilled at the summit of the Lomonosovfonna dome, Svalbard. The core covers about the past 800 years. The reliability of anion chemistry for paleoenvironmental studies, and various insoluble particles were also investigated. The ice core studied in this Thesis is the first relatively deep ice core from the central Svalbard that has been analyzed and the results interpreted and published at high resolution for all major ions.
One of the clearest features of the ion profiles is anthropogenic impact. SO4 2- and NO3- concentrations show significant increases by the mid-20th century with slight increases already at the end of the 19th century. In addition excess Cl- and NH4+ from anthropogenic sources are detected arriving after the mid-20th century. Anthropogenically derived SO4 2- and NO3- have different sources on Lomonosovfonna. NO3- is correlated with NH4+ and requires interpretation in terms of both natural and anthropogenic NH4/NO3 sources.
The ice core ionic load consists mostly of sea salt ions (Na+, Cl-, K+ and Mg2+). Water soluble Ca2+ are mostly terrestrial in origin. Ion balance together with the Na+/Cl- ratio shows considerable change about 1730 that is most probably due to Na2CO3 input to the ice cap before 1730. Marine biogenic CH3SO3- concentrations are high and stable during the Little Ice Age. CH3SO3- concentrations show a clear change in concentrations in 1920, that is the end of the Little Ice Age in Svalbard. Regardless of anthropogenic impact, marine biogenic SO4 2- is appreciable in total SO4 2- budget even in the 20th century.
The Laki volcanic eruption in Iceland in 1783 is identified in the ice core as a volcanic tephra layer and high SO4 2- concentration and acidity peaks. These show that SO4 2- arrived to the Lomonosovfonna ice cap 6–12 months later than insoluble tephra and the SO4 2- aerosol caused a drop in temperature.
The reliability of ice core ion chemistry analyses was estimated – for the first time in an ice core using two different analytical procedures on 500 adjacent samples from the same depth. Small-scale inhomogeneity in ion concentrations shows that information from ice core layers is representative of the regional environmental and suitable for paleoclimate studies.
Keywords: anions, Arctic, cations, ions, Laki, paleoclimate, particles, volcanic eruption
1.2 Ice core analyses
Ice core samples for chemical analyses are small and concentrations of chemical
components determined are generally rather low (Jauhiainen et al. 1999, Curran &
Palmer 2001). These facts require sophisticated chemical instruments that enable analyses
of low concentrations from small sample volumes. Numerous components (e.g. ions,
metals, gases, isotopes, organic compounds) can be analyzed and determined from ice
cores (e.g. Boutron et al. 1991, Anklin et al. 1995, Legrand & DeAngelis 1996, Barbante
et al. 1997, Townsend & Edwards 1998, Masclet et al. 2000, Burton et al. 2002, Lee et
al. 2002, Schuster et al. 2002).
Research on the insoluble parts of melted ice core samples has mainly
been focused on volcanic particles because of their importance for dating purposes
(Fiacco et al. 1994, Zielinski et al. 1997a). Other marine and terrestrial particles can also
provide a lot of knowledge about past climate and atmospheric composition (Zdanowicz
et al. 2000, Kohfelt & Harrison 2001).
2 Objectives of the Thesis
The main objectives of this Thesis were to determine water soluble ion concentrations
and analyze insoluble particles from the ice core, to investigate the reliability of ion
results, and to evaluate the significance of data from a climatic and environmental point
of view. The research site of this Thesis was Lomonosovfonna ice cap on Svalbard (Fig.
1), and this Thesis was based on a 121 m long ice core drilled from the highest ice field at
the summit of the Lomonosovfonna dome (78° 51' 53"N, 17° 25' 30"E, 1255 m a.s.l.) in
1997. The ice core covers approximately the past 800 years. More specifically, the main
aims were:
1) to prove that ice core ion concentrations are comparable using different ion
chromatographic methods and adjacent samples, and therefore are appropriate for
paleoclimate and environmental studies. This is the first time that duplicate chemical
analyses have done for such large number of samples. Adjacent samples from an ice core
at the same depth are generally assumed to give the same information even though the
concentrations of ions are extremely low, and the effects of snow accumulation, snow
drifting and partial melting are known to vary of over lengths comparable to the diameter
of an ice core (~10 cm).
2) to examine the origin of the ions and to assess the distribution of sources. To
interpret the past, the composition and origin of chemical impurities deposited in Arctic
snow must be known. Sources are generally marine, terrestrial, anthropogenic, biogenic
and volcanic.
3) to evaluate climatic, environmental and post-depositional changes from ice core ion
results. Different climatic periods and anthropogenic effects are sometimes possible to
detect using long term ion profiles because ions provide information on past atmospheric
composition. The LIA and the end of the LIA (in Svalbard 1920) and industrialization
should be observed in this ice core because it covers about the past 800 years.
4) to characterize the insoluble fraction of ice core samples. Svalbard ice cores have
not been subject to particle analysis before. Analyses give valuable information for
interpretation of ion results and have intrinsic value in themselves.
5.3 SO4 2- (Papers II and III)
In the Lomonosovfonna ice core SO4 2- was the next abundant ion after Na+ and Cl- and represented about 14% of total ions (Fig. 5). Sea salt and non-sea salt fractions are shown in Fig. 7 and clearly nss-SO4 2- was the dominant fraction. 74% of total SO4 2- was nss-SO4 2- and since 1950 over 88%. Only one volcanic eruption, the Laki, was easily detected (Section 5.3.1) and terrestrial SO4 2- usually was present together with Ca2+ (Section 5.6) and/or Mg2+. Therefore in the pre-anthropogenic period, most of the SO4 2- was from marine biogenic production (Section 5.4). In the 20th century CH3SO3H and SO4 2- concentrations had correlations over decadal periods (Fig. 7), such obvious co-variation indicated that biogenic SO4 2- is a major SO4 2- source even though anthropogenic inputs were already present. Models of the SO4 2- record also suggest that even in the 20th century marine biogenic sources were dominant accounting 30-55% of total SO4 2- budget.
5.7 Ion sources at different time periods (Paper VIII)
The ice core ion data can be naturally split into four groups: pre-industrial period that
was in the middle of the LIA, period immediately before the end of the LIA (before
1920), period immediately after the end of the LIA (after 1920), and period after 1950
dominated by anthropogenic input. Performing Principal Component Analysis (PCA) on
each group brought out the impact of bubbly and clear ice facies (caused by changes in
seasonal melting) and the nature of relationships between ions. PCA indicated that
climate variability is more dominant in the ice core as source of ionic variations than melt
water percolation. PCA showed that Na+ and Cl- were clearly from the same source in the
pre-industrial period. In the anthropogenic period Na+ and Cl- indicated excess Cl- from
anthropogenic sources. SO4 2- and NO3- were closer associated in the anthropogenic
period than pre-industrial period and this suggested anthropogenic pollution even though
ions were not from identical sources (Section 5.5). Before and after the end of the LIA
periods clear changes concerning CH3SO3- and SO4 2- can be seen. Change was also
noticed in concentration ratios (Section 5.4).
6 Conclusions
...
Ion concentrations in ice cores are so small that, from a chemistry point of view, there
is always doubt how accurate concentrations are. Therefore the reliability of anions
concentrations is an important part of the Thesis. It was shown that there are statistically
significant differences in mean concentrations for Cl- and SO4 2- , which are however,
explainable if only 2% of the samples have large differences in concentrations over a
distance of about 10 cm. This comparison also shows that glaciological noise level is not
remarkable, and it is less than the typical accuracy of IC measurements. Despite some
differences in concentrations, long term anion profiles are almost equal and therefore
adjacent samples measured by using two different procedures are repeatable and ice core
ion results are sound for paleoclimate and environmental studies.
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http://www.nsf.gov/pubs/1997/nsf97167/glacials.htmNear-surface processes affecting gas exchange: West antarctic ice sheet. Mary Albert, Cold Regions Research and Engineering Laboratory. This project will examine the physical processes that affect the manner in which heat, vapor, and chemical species in air are incorporated into snow and polar firn. The processes include advection, diffusion, and the effects of solar radiation penetration into the snow. An understanding of these processes is important because they control the rate at which reactive and nonreactive chemical species in the atmosphere become incorporated into the snow, firn, and polar ice and, thus, will affect interpretation of polar ice-core data. Currently, the interpretation of polar ice-core data assumes that diffusion controls the rate at which chemical species are incorporated into firn. This project will determine whether ventilation, or advection of the species by air movement in the firn, and radiation penetration processes have a significant effect. Field studies at the two west antarctic ice sheet deep-drilling sites will be conducted to determine the spatial and temporal extent for key parameters and boundary conditions needed to model the advection, conduction, and radiation transmission/absorption processes. An existing multidimensional numerical model is being expanded to simulate the processes and to serve as the basis for ongoing and future work in transport and distribution of reactive chemical species. (S-155)
... & much more....
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Review Signals of atmospheric pollution in polar snow and iceThe ice core data thus show that an increase of 25% has .... the reliability of ice core H202 data for atmospheric studies ...
journals.cambridge.org/article_S095410209000027X
.
.
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=222897Signals of atmospheric pollution in polar snow and ice
Abstract
In their upper layers, the polar ice sheets contain a detailed record of changes in the atmosphere over the industrial period. Measurements from air bubbles in ice have shown that the CO2 content of the atmosphere has increased by 25% in the last 200 years, and that of CH4 has more than doubled. Ice core records have demonstrated a close correspondence between greenhouse gases and temperature during the last glacial cycle. Profiles of radioactive species in snow clearly document nuclear bomb tests in the atmosphere, and the recent Chernobyl accident has also left a signal in Northern Hemisphere ice. Nitrate has more than doubled in Greenland snow over the industrial period, while sulphate has more than trebled. No significant trend is seen in Antarctic snow for these anions. Pb increased 100-fold until the 1970s in Greenland snow, but concentrations appear now to be declining. A small increase is also recorded in Antarctic snow. Organochlorine compounds offer great potential for pollution studies in snow. The ability to study global scale pollution in polar ice could be hampered if there is significant local pollution. In Antarctica, impact on the atmosphere from local human activities is still mainly confined to small areas near stations.
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U.S. National Ice Core LaboratoryHome site for the US National Ice Core Laboratory at the US Geological Survey in Denver, Colorado, USA.
nicl.usgs.gov/
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http://epic.awi.de/Publications/Det2001a.pdfRecent Greenland Accumulation Estimated from Regional Climate Model Simulations
and Ice Core Analysis*
ABSTRACT
The accumulation defined as ‘‘precipitation minus evaporation’’ over Greenland has been simulated with the high-resolution limited-area regional climate model HIRHAM4 applied over an Arctic integration domain. This simulation is compared with a revised estimate of annual accumulation rate distribution over Greenland taking
into account information from a new set of ice core analyses, based on surface sample collections from the North Greenland Traverse. The region with accumulation rates below 150 mm yr21 in central-northwest Greenland is much larger than previously assumed and extends about 500 km farther to the south. It is demonstrated that good agreement between modeled and observed regional precipitation and accumulation patterns exists, particularly concerning the location and the values of very low accumulation in the middle of Greenland. The accumulation rates in the northern part of Greenland are reduced in comparison to previous estimates. These minima are connected with a prevailing blocking high over the Greenland ice sheet and katabatic wind systems preventing humidity transports to central Greenland. The model reasonably represents the synoptic situations that lead to precipitation. Maxima of precipitation and accumulation occur at the southwestern and southeastern coasts of Greenland and are connected with cyclonic activity and the main storm tracks around Greenland. The central region of the Greenland ice sheet acts as a blocking barrier on moving weather systems and prohibits cyclones moving from west to east across this region and, thus prevents moisture transports.
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http://nicl-smo.unh.edu/icwg/ICWG1988.pdfOrganization of Specialty Groups (e.g., stable isotopes in ice, gases and isotopes of gases, cosmogenic isotopes, trace metals, major anions and cations, organic compounds and other trace constituents, physical and mechanical properties, borehole studies, atmospheric studies, modeling and GISP H Site Selection Panel Meeting). Speciality Group meetings will be assigned to rooms in Science and Engineering Research Building.
...
A deep core to bedrock at/near Summit in Greenland to obtain a long paleoenvironmental record. This would be the first detailed terrestrial record covering several glacial-interglacial cycles and allow study of the three Milankovitch cycles of ~ 2 x 10^4, 4 x 10^4, and 10^5 years. To assure bedrock was reached one needs to penetrate bedrock and recover some bedrock core. It is highly desirable that the results from such a core can be compared with those from a core nearby, analyzed independently, to safeguard against analysis problems and ice flow related artifacts in the deep core record. Comparison of the two deep cores with each other and with existing intermediate and deep Greenland ice cores will indicate whether additional intermediate cores and/or cores penetrating the last glacial are needed. An array of shallow cores and snow pit studies is needed to determine spatial variability.
...
SPECIALTY GROUP REPORT: TRAPPED GAS COMPOSITION
Justification:
Analyses of air bubbles embedded in polar ice reveal the composition of the preindustrial and ancient atmospheres. So far, extensive measurements of carbon dioxide, methane, nitrous oxide and some chlorocarbons have been made on ice cores from both polar regions. The results provide a remarkable record of the magnitude and timing of
human influences on the global cycles of these gases. Except for the chlorocarbons, for which there is no evidence of any substantial pre-industrial concentrations, the other gases (CO2, CH4 and N20) started increasing only during the last 200 years with the growing population and increasing needs for energy and food. The increase of N20 probably started only a few decades ago. The record shows that C02 concentrations were about 280 ppmv 200 years ago while methane and nitrous oxide concentrations were about 700 ppbv and 285 ppbv respectively. Today there is 25% more C02, 8% more N20, and 100% more CH4 in the atmosphere.
Measurements on existing ice cores provide longer records for C02 and CH4 which show large natural variations during glacial and interglacial periods. The Bern and Grenoble groups have published data that provides a convincing case that the C02 content of the atmosphere during glacial time (~ 200 ppmv) was substantially lower than that for the interglacial time (~ 280 ppmv).
Recent experiments by the Bern and Grenoble ice core groups show that the concentration of CH4 dipped to a low of about 350 ppbv during the last ice age. Khalil and Rasmussen's (in press) data spanning the Little Ice Age between 1450 and 1750 show a proportionate decrease in methane (about 40 ± 30 ppbv/°K) and also a decrease of N20 (about 5 ± 3 ppbv/°K). These decreases are believed to be a measure of the response of emissions from the Earth's soils, oceans, and high northern wetlands to global climatic change. The character and details of the transition of the atmospheric concentrations of C02, CH4 and N20 during the last deglaciation have yet to be well documented.
Nevertheless, it is clear that concentrations of the radiatively active gases in air influence climate and are in turn influenced by climate. The large role which varying levels of radiatively active gases play in climate change emphasizes the importance of understanding the global-scale interactions between climate and the biosphere. Studies of the d13C of C02,d13C and dD of CH4, d15N of N20, d180 Of 02, and the 02:N2:Ar ratio in the trapped gas can help in achieving this understanding. The importance of studying these variables lies not in their environmental influence, but in their role as tracers of selected geochemical processes that influence global climate. d13C of C02 serves as a tracer for studying the roles of the ocean and terrestrial biosphere in changing atmospheric pCO2. d13C and dD of CH4 reflect the relative production rates by the different sources. The same is true for the d15N of N20. d180 of 02 is governed by isotope fractionation during photosynthesis, respiration, and hydrologic Processes. Hence it reflects global scale interactions between the hydrosphere, biosphere and atmosphere. The atmospheric 02 concentration (expressed as the 02/N2 or 02/Ar ratio) indicates changes in the magnitude of the reduced carbon reservoirs, as well as the metabolic C02 content of the deep sea. N2/Ar, the d15N of N2, and 3He/4He must have been constant in the ice age atmosphere, and serve as indicators of the integrity of
trapped gas samples.
In summary, studies of the composition of trapped gases in ice cores inform us directly about changes in the atmospheric concentrations of the radiatively active gases. They also reveal the composition of various tracers, which can help us unravel the nature and causes of Pleistocene climate change.
...
d13C of C02
Atmospheric C02 exchanges with the biosphere and the oceans. The size of the biosphere may vary as climatic changes, and the uptake or release of C02 by the oceans is governed by pCO2 of the ocean surface waters, which depends on a number of factors. d13C and the 14C/12C ratio of C02 can be used to learn whether atmospheric C02 concentration changes are due to biospheric or oceanic exchange. Atmospheric d13CO2 (~ -7°/oo PDB) is closer to that of the oceans (+2 °/oo) than to the more depleted biosphere (~ - 25°/oo); the radiocarbon in the biosphere and atmosphere are about equal, while the surface waters of the ocean are somewhat lower (~95%). Thus if, for example, an atmospheric increase in C02 were caused by a net flux from the biosphere, the 13C/12C
ratio would decrease, with almost no change in 14C/12C. On the other hand, if a C02 increase is the result of a predominant influx from the oceans, the 13C/12C ratio would be minimally affected and the 14C/12C ratio would decrease. The expected variations in d13C are small and thus extreme care is required in the experimental techniques.
At the proposed drilling site in Central Greenland one expects to encounter the ice conditions most favorable for obtaining a detailed C02 concentration record during glacial and interglacial times. High depth resolution measurements can be performed and compared to d180 of H20 (and particulate content, chemical species, and the
concentrations of cosmogenic radio-nuclides), in order to determine the relative timing of C02 and climate variations, and therefore the causal relationship. Ultimately the achievable resolution is determined by the inherent age difference of enclosed air and surrounding ice, which can vary with time.
The atmospheric 02 concentration, expressed as the 02/Ar ratio, is affected by the carbon cycle via photosynthesis and respiration. The processes thought to be responsible for changing atmospheric C02 levels leave different imprints on the atmosphere C02 content. The burial of organic carbon or production of terrestrial biomass raises the 02 concentration in air, erosion or destruction of biomass decreases 02. Changes in the transport of organic carbon to the deep sea have the same effect. Reactions between C02, CaC03 and oceanic HC03- can change atmospheric C02 but have no effect on the 02/Ar ratio. The measurement of the variable thus provides an important constraint for unravelling the behavior of the carbon system and understanding the causes of variations
in the atmospheric C02 content.
C. Post-Deposition Processes
A number of investigators have shown that contaminant concentrations in snow
may change with time as the snow ages, even in the absence of dry deposition. Examples
of process affecting these concentrations include snow sublimation, meltwater
percolation, and diffusion of contaminants through the snowpack. Possible research
methods to explore post-deposition changes in the Arctic include the following:
1. Measurement of contaminant concentrations in surface snow during dry periods
of varying length between storms is needed to assess sublimation. Comparing timevarying
concentrations for species with and without appreciable dry deposition may help
separate the effects of sublimation.
2. Measurement of contaminant concentrations in shallow snowpits are needed for
comparison with previous measurements of concentrations in fresh snow corresponding
to the same set of storms. This will provide an indication of changes in concentration
between the original fresh snow and the older snow in the pits.
3. Statistical analysis of concentrations in intermediate depth cores is needed for
species whose airborne concentrations and deposition rates are believed to have been
constant over the period of the cores. This may identify longer term post-deposition
changes in concentration.
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http://www.nap.edu/openbook.php?record_id=10136&page=25A review of available Greenland ice-core data is given by Alley (2000). The data were collected by two international teams of investigators from multiple laboratories. The duplication shows the high reliability of the
data from the cores over the most recent 110,000 years, and the multiparameter analyses give an exceptionally clear view of the climate system.
...and see the graph at:
http://www.nap.edu/openbook.php?record_id=10136&page=260-0
http://www.globalchange.umich.edu/globalchange1/current/lectures/samson/climate_patterns/Both methane and carbon dioxide correlate with temperature - i.e., an increase in temperature is associated with an increase in the abundance of both these two gases. It is unclear whether the gas abundance changes are a consequence of the temperature changes or vice versa.
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AAPG Studies in Geology 47: Geological Perspectives of Global ...... judge the reliability of forecasts made by global climate change models. ... Although numerous statistical analyses have been made of the ice-core data, ...
search.datapages.com/data/specpubs/study47/CH11/ch11.htm - 51k -
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Atmospheric CO fluctuations during the last millennium ...evolution than suggested by ice-core data. Coupled to centennial-scale cooling .... correspondence corroborates the reliability of the older reconstructed ...
geology.geoscienceworld.org/cgi/reprint/33/1/33.pdf
http://geology.geoscienceworld.org/cgi/content/abstract/33/1/33Geology; January 2005; v. 33; no. 1; p. 33-36; DOI: 10.1130/G20941.1
"Atmospheric CO2 fluctuations during the last millennium reconstructed by stomatal frequency analysis of Tsuga heterophylla needles"
A stomatal frequency record based on buried Tsuga heterophylla needles reveals significant centennial-scale atmospheric CO2 fluctuations during the last millennium. The record includes four CO2 minima of 260–275 ppmv (ca. A.D. 860 and A.D. 1150, and less prominently, ca. A.D. 1600 and 1800). Alternating CO2 maxima of 300–320 ppmv are present at A.D. 1000, A.D. 1300, and ca. A.D. 1700. These CO2 fluctuations parallel global terrestrial air temperature changes, as well as oceanic surface temperature fluctuations in the North Atlantic. The results obtained in this study corroborate the notion of a continuous coupling of the preindustrial atmospheric CO2 regime and climate.
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http://www.antarctica.ac.uk/mdms/cgi-bin/view.pl?pd_pkey=93419639663811BAS MDMS Details... what processes can occur, and of testing the reliability of models, is to look into the past. ... Parent (up), Ice Core data - BAS - high level 'parent' ...
www.antarctica.ac.uk/mdms/cgi-bin/view.pl?pd_pkey=93419639663811 - 10k -
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http://www.agu.org/pubs/sample_articles/sp/2001GL013781/2001GL013781.pdf"Our model can explain the observed lag of several thousand years of atmospheric CO2 behind temperature upon entering a stadial, given reasonable assumptions about the precipitation-weighted temperature record at Vostok."
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http://www.env.gov.bc.ca/soerpt/files_to_link/2000tecdocs/06-climate-techdoc.pdfMethodology and Reliability: Atmospheric carbon dioxide levels from 1744 to 1973 were
derived from air bubbles trapped in the ice at the Siple Station, West Antarctica (75º55'S,
83º55'W). The date of air isolation can be determined by considering the age of the ice
and the process by which the air bubbles are trapped. At shallow depths, atmospheric air
still circulates through the open pores, resulting in enclosed air that is much younger than
the surrounding ice. The isolation of air in bubbles from the atmosphere occurs between
the depths of 64 and 76 metres. On the basis of porosity measurements, researchers
determined that the time lag between the mean age of the trapped gas and the surrounding
ice was 95 years and that the isolation process occurred over 22 years. Neftel et al. (1985)
concluded that the atmospheric carbon dioxide concentration circa 1750 (pre-industrial)
was 280 +/- 5 parts per million by volume (ppmv); it had risen to 345 ppmv in 1984 (a
22.5% increase), essentially as a result of human influences. For a detailed account of the
methodology used for deriving the ice core data, see Neftel et al. (1985).
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http://www.cup.cam.ac.uk/uk/catalogue/catalogue.asp?isbn=9780521824095&ss=excClimate Change in Prehistory
The End of the Reign of Chaos
The dramatic advance with ice cores came with the publication in the early 1990s of the first results of two major international projects: the Greenland Ice Sheet Project Two (GISP2) (Grootes et al., 1993) which successfully completed drilling a 3053-m-long ice core down to the bedrock in the Summit region of central Greenland in July 1993; and its European companion project, the Greenland Ice Core Project (GRIP) (Greenland Ice Core Project Members, 1993), which one year earlier penetrated the ice sheet to a depth of 3029m, 30km to the east of GISP2. These cores provided a completely new picture of the chaotic climate throughout the last ice age, the turbulent changes that occurred at the end of this glacial period and the stability of the climate during the last 10kyr (a period known as the Holocene).
These chaotic changes were evident in many of the ice-core parameters, including rapid fluctuations in the snowfall from year to year and sudden changes in the amount of dust swept up from lower latitudes. The most spectacular results were obtained, however, by measuring the ratio of oxygen isotopes (oxygen-16 and -18), which provided an accurate record of regional temperature over the entire length of the ice core. The amount of the heavy kind of oxygen atoms, oxygen-18 (18O), compared with the lighter far more common isotope oxygen-16 (16O), is a measure of the temperature involved in the precipitation processes. But this is not a simple process.
...
These cores presented an entirely different picture of the climate during and following the last ice age. Added to the glacial slowness of changes that led to the building and decline of the huge ice sheets was a whole new array of dramatic changes (Fig. 1.2). While these long-term consequences remained, two exciting features emerged from the detailed record of the ice cores. First, they provided much improved evidence of the frequent fluctuations in the climate on the timescales of millennia that ranged from periods of intense cold to times of relative warmth. Second, and even more interesting, these longer-term variations were overlain with evidence of dramatic short-term fluctuations: over Greenland, annual average temperatures rose and fell by up to 10 °C in just a few years, while annual snowfall trebled or declined by a third. As the research team memorably described the patterns (Taylor et al., 1993), the climate across the North Atlantic behaved like a ‘flickering switch’.
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http://www.nature.com/nature/journal/v440/n7087/full/nature04679.htmlThe magnitude and impact of future global warming depends on the sensitivity of the climate system to changes in greenhouse gas concentrations. The commonly accepted range for the equilibrium global mean temperature change in response to a doubling of the atmospheric carbon dioxide concentration1, termed climate sensitivity, is 1.5–4.5 K (ref. 2). A number of observational studies3, 4, 5, 6, 7, 8, 9, 10, however, find a substantial probability of significantly higher sensitivities, yielding upper limits on climate sensitivity of 7.7 K to above 9 K (refs 3–8). Here we demonstrate that such observational estimates of climate sensitivity can be tightened if reconstructions of Northern Hemisphere temperature over the past several centuries are considered. We use large-ensemble energy balance modelling and simulate the temperature response to past solar, volcanic and greenhouse gas forcing to determine which climate sensitivities yield simulations that are in agreement with proxy reconstructions. After accounting for the uncertainty in reconstructions and estimates of past external forcing, we find an independent estimate of climate sensitivity that is very similar to those from instrumental data. If the latter are combined with the result from all proxy reconstructions, then the 5–95 per cent range shrinks to 1.5–6.2 K, thus substantially reducing the probability of very high climate sensitivity.
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http://www.lyellcollection.org/0-0
http://www3.interscience.wiley.com/journal/112731066/abstractJournal of Quaternary Science; Volume 10 Issue 1, Pages 77 - 82; Published Online: 26 Jul 2006
DOI: 10.1002/jqs.3390100108
Abstract
Data from the Greenland ice sheet and continental records from Europe have indicated climatic fluctuations during the last interglacial (Eemian: Oxygen Isotope Substage 5e). Similar fluctuations have not, however, been documented previously from marine environments. Here, we show the existence of two cold events during substage 5e in two marine, benthic foraminiferal, shelf records from northwest Europe and suggest that these cooling events are a result of fluctuations in the strength of the North Atlantic surface-water circulation.
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http://www.nzic.org.nz/CiNZ/articles/Mackie_71_3.pdfChemistry in New Zealand October 2007
"Climate Change Mythconceptions: Some Incorrect, Irrelevant
and Misleading Arguments Made by Climate Change Denialists"
Several good ice core records have been obtained from Antarctica. Two of the best long ice core records are those of the European Project for Ice Coring in Antarctica (EPICA) and a core taken at Vostok Station. The EPICA core goes back about 740,000 years and covers 8 ice ages (or glacial cycles) and the Vostok core goes back about 420,000 years, covering 4 glacial cycles. The Vostok core was drilled in 1996 and the EPICA core in 2004, and not all EPICA analysis is complete yet. However, there is complete temperature (from isotopes) and CO2 data (from
bubbles) available for Vostok so the discussion here uses only the Vostok measurements.
...tomorrow... Part II
...maybe....
