a 352 year record of summer temperature reconstruction in the western tianshan mountains china as deduced from tree ring density three robust tree ring density chronologies were developed for the western tianshan mountains of northwestern china the chronologies were significantly correlated and form a regional chronology gld the gld had significant and positive correlations with temperature of warm seasons based on this relationship the mean minimum temperatures of may to august were reconstructed using the gld chronology for the period ad 1657 to 2008 the temperature reconstruction exhibited temperature patterns on interannual to centennial timescales and showed that the end of the 20th century is the warmest period in the past 352 years the reconstructed temperature variation has a teleconnection with large scale atmospheric oceanic variability and captures long and broad scale regional climatic variations

minimum winter temperature reconstruction from average earlywood vessel area of european oak quercus robur in n poland abstract tree ring based temperature reconstructions form a substantial part of the international proxy data base used to examine and model global climate variations of the last millennium however most tree ring based reconstructions are derived from study sites in the high latitudes or high altitudes paying very little attention to low elevation sites thus a large gap in the geographical coverage of climate reconstructions from temperate low elevation sites in central europe still exists this motivated us to concentrate our efforts on the european oak quercus robur in n poland we developed a new robust tree ring width chronology trw as well as four wood anatomical chronologies e g average vessel area and number of vessels from q robur for the period 1810 to 2010 the chronologies were examined for their climatological responses while trw was found to have weak correlations with climate the earlywood vessel parameters evp especially average vessel area ava revealed significant positive correlations to minimum winter temperatures based on stable climate growth correlations a reconstruction of minimum winter temperatures 29th november to 20th january back to 1810 was performed for north poland the reconstruction indicates a promising potential to reveal low frequency climate information an additional extreme year analysis suggested that in cold winters a cold warm cold pattern in the minimum temperatures was responsible for the relatively small earlywood vessels spatial field correlations imply that our reconstruction is more related to temperature variations towards the east of europe the reconstructed temperature compared well with two existing temperature reconstructions especially during most of the 20th century even though the temperature reconstructions differ spatially and temporally based on these findings the relatively extensive resource of archeological oak material from this region may be useful to perform multicentennial climate reconstructions in the temperate climate zone

discovery of early holocene wood and peat on the forefield of the pasterze glacier eastern alps austria during recent years a number of fragments of pinus cembra and larix decidua as well as peat were found in front of the tongue of the pasterze glacier in the eastern alps these were washed out by the stream from under the present ice the wood originates from trees which reached ages of upto 400 years or more radiocarbon dating shows them to come from the early holocene they indicate that between cal bc 8100 and cal bc 6900 the pasterze glacier was smaller than at present the pasterze glacier advanced around cal bc 6900 a lump of peat shows that around cal bc 6300 at the latest the pasterze glacier was again smaller than today the radiocarbon age of the fulvic acid fraction of thepeat suggests that growth could have continued until cal bc 5430 5080 further wood samples dated to around cal bc 4800 and cal bc 3800 show that at these times the pasterze glacier was smaller than at present the pasterze glacier had a relatively limited extent over long periods inthe early holocene thus mostly favou

annual climate variability in the holocene interpreting the message of ancient trees abstract over vast areas of the world s landmasses where climate beats out a strong seasonal rhythm tree growth keeps unerring time in their rings trees record many climate melodies played in different places and different eras recent years have seen a consolidation and expansion of tree ring sample collections across the traditional research areas of north america and europe and the start of major developments in many new areas of eurasia south america and australasia from such collections are produced networks of precisely dated chronologies records of various aspects of tree growth registered continuously year by year across many centuries their sensitivities to different climate parameters are now translated into ever more detailed histories of temperature and moisture variability across expanding dimensions of time and space with their extensive coverage high temporal resolution and rigid dating control dendroclimatic reconstructions contribute significantly to our knowledge of late holocene climates most importantly on timescales ranging from 1 to 100 years in special areas of the world where trees live for thousands of years or where subfossil remnants of long dead specimens are preserved work building chronologies covering many millennia continues apace very recently trees have provided important new information about major modes of general circulation dynamics linked to the el nino southern oscillation and the north atlantic oscillation and about the effect of large volcanic eruptions as for assessing the significance of 20th century global warming the evidence from dendroclimatology in general supports the notion that the last 100 years have been unusually warm at least within a context of the last two millennia however this evidence should not be considered equivocal the activities of humans may well be impacting on the natural growth of trees in different ways making the task of isolating a clear climate message subtly difficult

synchronous climatic change inferred from diatom records in four western montana lakes in the u s rocky mountains late holocene environmental and climatic conditions were reconstructed from diatom assemblages in sediment cores from four western montana lakes crevice lake foy lake morrison lake and reservoir lake the lakes show synchroneity in timing of shifts in diatom community structure but the nature of these changes differs among the lakes two of the sites provide highly resolved records of hydrologic balance while the other two stratigraphic sequences primarily record temperature impact on lake thermal structure all four lakes show significant change in five discrete intervals 2200 2100 1700 1600 1350 1200 800 600 and 250 cal yr bp the similarities in the timing of change suggest overlying regional climatic influences on lake dynamics the 800 600 cal yr bp shift is evident in other paleorecords throughout the great plains and western us associated with the transition from the medieval climate anomaly to the little ice age large scale climatic mechanisms that influence these lake environments may result from atmospheric circulation patterns that are driven by interactions between pacific and atlantic sea surface temperatures which are then locally modified by topography

paleogene calcite compensation depth in the eastern subtropical pacific answers and questions 1 ocean drilling program leg 199 drilled a north south transect across the eocene paleoequator in the eastern pacific permitting reconstruction the calcite compensation depth ccd since earliest eocene time the ccd was relatively shallow near the early eocene pacific equator 3200 m and unlike modern latitudinal ccd gradients deepened to the north to 3600 m paleolatitude 10 n at 41 ma the ccd underwent a brief sharp transient deepening of 700 m then remained shallow until the eocene oligocene boundary at the e o boundary the ccd deepened by 1200 m in less than 300 kyr this rapid deepening served to more than double the area of seafloor subject to caco3 deposition sea level fall associated with ice volume buildup and ensuing shelf basin fractionation is unlikely to be the sole cause of the increased deep ocean caco3 burial rather a sudden rapid increase in the amount of ca entering the ocean appears necessary to explain the observations

neogene history of the calcite compensation depth and lysocline in the south pacific ocean the depth time pattern of calcite accumulation recorded at deep sea drilling project dsdp sites beneath the oligotrophic subtropical gyre in the south east pacific ocean allows us to define here both the calcite compensation depth ccd and the lysocline the neogene ccd history is one of shoaling before 15 or 20 myr and subsequent deepening to the present level of 4 100 m a broad zone of increased calcite dissolution 600 m thick formed during early to middle miocene time and has remained this zone the lysocline denotes an important change in ocean chemistry and may reflect either an increase in the volume of more corrosive deep water beginning about 18 myr and reaching steady state by 14 myr the time of rapid ice build up in antarctica or an increase in calcite rain rate caused by an increase in surface water productivity

variations in the fine scale composition of a central pacific ferromanganese crust paleoceanographic implications a 47 to 60 mm thick fe mn crust from horizon guyot water depth 1800 1780 m central pacific was used to evaluate the potential of crusts as recorders of neogene paleoceanographic and paleoclimatic conditions the chemical composition was determined by microprobe for 16 elements from a polished thin section three analyses were made per millimeter and averaged to give the composition of each millimeter the age of the crust was determined by measuring the strontium isotope composition of the crust and comparing it with the tertiary seawater curve the crust represents 18 5 m y of growth of fe and mn oxyhydroxides the crust is composed of alternating botryoidal and laminated layers the botryoidal layers formed during the same time intervals that widespread neogene deep sea hiatuses were forming in bottom sediments the botryoidal layers represent growth during times of intensified deepwater flow whereas the laminated intervals represent more quiescent conditions the correspondence between the botryoidal layers and the neogene hiatuses is so strong that we were able to choose a variable growth rate model over a constant growth rate model for the crust chemical changes in the crust take two forms the first is represented by broad changes in the composition defined chiefly by fourth order polynomial fits to the chemical profiles of each element with depth in the crust the second is high frequency changes in composition the broader changes occurred primarily at about 15 11 5 7 4 6 4 5 2 and 4 6 ma which may correlate with major changes in paleoceanographic circulation and development of ice caps at the poles the periods of the high frequency changes may reflect climatic changes that resulted from orbital forcing these high frequency changes may correspond to the high order eccentricity periods of 3 47 2 04 and 1 31 m y

can climate variations be inferred from tree ring parameters and stable isotopes from larix decidua juvenile effects budmoth outbreaks and divergence issue abstract larch wood has been used for centuries as a building material hence the study of the tree ring width the latewood maximal density and the oxygen and carbon isotope composition of the cellulose of this tree provides potential and valuable insights when reconstructing past climate variability we explore the qualities and limitations of these proxies focusing on a forest standing the nevache valley french alps the analysis of 15 trees demonstrates a small intra tree variability in comparison with the inter tree variability of 13c and 18o and shows that 6 trees at least must be pooled to make a population representative sample our results show no juvenile effect for 13c unlike tree ring width and density 13c and 18o are not altered by budmouth outbreaks these two parameters therefore appear well suited for climate reconstructions and depict a strong correlation with july august temperature and relative humidity the 18o of larch cellulose is also strongly linked with the previous winter december march oxygen isotopic composition of the precipitation this is consistent with a winter water recharge of soil and ground the past variations of july august maximum temperature and relative humidity were established using two different combinations of the isotopic ratios uncertainties on the reconstructions are estimated respectively at 1 4 c and 3 6 inter annual variations of temperature and relative humidity are well reproduced however the reconstructed july august temperature series diverges from the instrumental one being lower after ca 1990 the effects of the variation through time of the depth of source water and of the ecophysiological response of trees to rising co2 on the isotope composition are discussed as possible causes of divergence this divergence problem strongly questions the possibility of producing appropriate isotope based temperature calibration the relationships between isotopes and the july august relative humidity are more stationary than those with temperature this may reflect the first order control of the relative humidity on 13c via the stomatal conductance and its influence on the evaporative enrichment of the oxygen of the leaf water our study suggests that past variations of relative humidity in the french alps can be accurately estimated using the stable isotope composition of larch cellulose

climatic change and caco3 preservation an 800 000 year bathymetric reconstruction from the central equatorial pacific ocean sixteen deep sea cores from the central equatorial pacific are used to reconstruct a continuous 800 000 year 800 kyr record of bathymetric variations in carbonate preservation as measured by calcium carbonate caco3 content the depth of the sedimentary lysocline has fluctuated markedly in conjunction with late pleistocene climate cycles while the carbonate critical depth ccrd which is the water depth where the sediments contain 10 caco3 has remained relatively constant as a result the depth of the lysocline controls the bathymetric position and thickness of the caco3 transition zone defined as the depth from the lysocline to the ccrd modern and interglacial aged sediments show poor caco3 preservation and thick caco3 transition zones glacial aged sediments show good preservation and deep thin zones due to the deepening of the lysocline detailed comparison of the caco3 preservation and oxygen isotope records from the central equatorial pacific confirms the observation that preservation maxima and minima tend to occur during the latter half of glacial and interglacial stages and on climate transitions rather than during the middle of climatic stages during the nine major glacial stages of the last 800 kyr the lysocline deepened by at least 400 to 800 m this deepening indicates an increase in the abyssal carbonate ion concentration co3 and a depression of the calcite saturation horizon best explained by the deeper presence of a more carbonate saturated water mass the bottom of the transition zone has remained at a relatively constant depth during the brunhes chron indicating a balance between caco3 sedimentation and dissolution in the deepest waters of the central equatorial pacific

continuous marine radiocarbon reservoir calibration and the 13c suess effect in the irish sea results from the first multi centennial shell based marine master chronology abstract the identification in various proxy records of periods of rapid decadal scale climate change over recent millennia together with the possibility that feedback mechanisms may amplify climate system responses to increasing atmospheric co2 highlights the importance of a detailed understanding at high spatial and temporal resolutions of forcings and feedbacks within the system such an understanding has hitherto been limited because the temperate marine environment has lacked an absolute timescale of the kind provided by tree rings for the terrestrial environment and by corals for the tropical marine environment here we present the first annually resolved multi centennial 489 year absolutely dated shell based marine master chronology the chronology has been constructed by detrending and averaging annual growth increment widths in the shells of multiple specimens of the very long lived bivalve mollusc arctica islandica collected from sites to the south and west of the isle of man in the irish sea the strength of the common environmental signal expressed in the chronology is fully comparable with equivalent statistics for tree ring chronologies analysis of the 14c signal in the shells shows no trend in the marine radiocarbon reservoir correction r although it may be more variable before 1750 the 13c signal shows a very significant r2 0 456 p

neogene history of the south pacific tradewinds evidence for hemispherical asymmetry of atmospheric circulation rea d k and bloomstme m k 1986 neogene history of the south pacific tradewmds evidence for hemlsphermal asymmetry of atmospherm circulation palaeogeogr palaeochmatol palaeoecol 55 55 64 eohan dust grains extracted from southeast pacific pelagic sediments provide a neogene record of southern hemisphere atmospherm processes the mass accumulation rate of dust has been low and generally constant at 1 4 mg cm 2 103 y since the late ohgocene eohan grains ze data show an increase from 8 20 3 40 t m older sediments to 7 20 6 80 t m younger materml this shift occurred about 10 5 m y ago and reflects a s gmfmant increase in the intensity of atmospheric circulation then there s no obwous response to the onset of northern hemisphere glacmtmn 2 5 m y ago m these eohan records from the south pacific compamson with existing lnformatmn from the northern hemisphere suggests that the southern hemisphere has had more intense atmospheric circulation throughout the neogene and that this asymmetry reached its greatest extent between 10 5 and 2 5 ma

frequency dependent signals in multi centennial oak vessel data article i nfo article history this work evaluates whether vessel size data contain a coherent spring precipitation signal over different frequency domains and how this climatic information varies from the signal encoded in radial growth the study was conducted at a forest site dominated by old oak trees quercus petraea mattuschka liebl located in the southern part of the swiss alps measurements of earlywood vessel size of 27 cores from 12 oak trees were performed in order to build an unprecedented multi centennial vessel size chronology age independent long term growth changes and climatic responses in the high mid and low frequency domains of differently composed chronologies are explored to test the stability of the signals results are compared with analyses of tree ring width measurements from the same material to gain a deeper understanding of physiological processes we find that mean vessel size data in contrast to tree ring width carry a frequency dependent signal although the signal of both parameters is similar in the low frequency domain the climate response in the high frequency domain differs vessel size responds negatively to wet spring conditions whereas ring width mainly responds positively to water availability during the summer we hypothesize that the processes responsible for signal registration in the specific frequencies are different the differing high frequency signals appear to be directly linked to dissimilar responses to weather conditions driving ring and vessel formation in contrast the long term response is related to conditions that affect tree vigour and due to a positive feedback on growth is indirectly reflected in the vessels and ring width characteristics due to the change in the frequency related response observed in this pioneering study it appears that the mean earlywood vessel size of oak is not an adequate proxy for long term reconstruction of spring precipitation

dendro provenancing of arctic driftwood abstract arctic driftwood may represent a cross disciplinary proxy archive at the interface of marine and terrestrial environments which will likely gain in importance under future global climate change circumpolar network analyses that systematically consider species specific boreal origin areas transport routes and deposition characteristics of arctic driftwood are however missing here we present tree ring width trw measurements of 2412 pine larch and spruce driftwood samples from greenland iceland svalbard the faroe islands and the lena delta in northeastern siberia representing the largest arctic driftwood trw compilation these data are compared against 495 trw reference chronologies from the boreal forests of eurasia and north america the southern yenisei region is the main source for recent pine driftwood at all arctic sampling sites whereas spruce mainly originates in western russia and central siberia as well as in northern north america larch driftwood is for the first time dendro provenanced to central and eastern siberia a new larch driftwood chronology extends the middle lena river reference chronology back to 1203 ce annually resolved radiocarbon measurements further date six larch driftwood chronologies between 1294 and 2013 ce although being highly replicated our study emphasizes the importance of interdisciplinary research efforts including radiocarbon dating isotopic tracing and adna processing for improving arctic driftwood provenancing in space and time if successful arctic driftwood studies will contribute to the reconstruction of past boreal summer temperature variations and ocean current dynamics as well as changes in sea ice extent and relative sea level over the last centuries to millennia

a last millennium temperature reconstruction using chironomids preserved in sediments of anoxic seebergsee switzerland consensus at local regional and central european scales determining if temperatures of the last century exceed natural variability necessitates the use of high resolution paleo reconstructions extending beyond the instrumental data i e 150 years although syntheses using tree ring stalagmite and borehole based reconstructions are available biological proxies preserved in lake sediments have been neglected as a source of high resolution information on climate change here we present a decadal scale mean july air temperature reconstruction covering the past millennium from varved seebergsee switzerland this reconstruction is compared to instrumental data at local regional and european scales to another high resolution chironomid inferred temperature reconstruction from lake silvaplana switzerland to a composite of paleo climate reconstructions from the greater alpine region and to various millennial scale climate reconstructions from the northern hemisphere when compared to local and regional instrumental records since ca 1760 ad significant p 0 5 are obtained suggesting that chironomids accurately register the changes in temperature for the past ca 250 years at european scale the seebergsee reconstruction correlates rpearson 0 40 p 0 01 with instrumental and early instrumental data back to 1500 ad on the millennial time scale the chironomid reconstruction of seebergsee provides a pattern of temperature changes mirrored by the chironomid reconstruction from silvaplana rpearson 0 44 p 0 01 and the greater alpine region composite of reconstructions rpearson 0 40 p 0 01 this includes warmer than the last century mean july air temperatures 1 2 c on average during the end of the medieval climate anomaly mca and colder than the last century temperatures 0 5 c on average during the little ice age both chironomid reconstructions inferred a warming during the last decades but this chironomid inferred warming does not exceed the mca temperatures this result is not singular as many millennial temperature reconstructions in the northern hemisphere do not show unprecedented warming of the last century at local regional scale however the chironomid assemblages found in seebergsee and silvaplana since ca 1950 ad seem to be unique i e they show unprecedented assemblage compositions for the past 1000 years

summer temperature patterns over europe a reconstruction from 1750 a d based on maximum latewood density indices of conifers abstract temperature variations over europe are reconstructed for a 6 month summer season from april to september for the period 1750 1850 using a network of maximum latewood density chronologies of coniferous trees around 44 of the variance of the whole temperature grid was explained in calibration independent verification indicates that over the reconstruction period the explained variance averaged over the whole grid should lie in the range 30 to 35 the reconstructions are better in the north of the region about 50 explained temperature variance based on comparison with independent climate data than in the south below 20 the temperature recontructions indicate cooler summers over europe from 1812 to 1816 and during the 1830s the summers of the 1820s were the warmest reconstructed decadal variations occur on a regional scale but no similar periods of anomalously cooler or warmer summers occurred between 1750 and 1810 throughout europe

cycles and shifts 1 300 years of multi decadal temperature variability in the gulf of alaska the gulf of alaska goa is highly sensi tive to shifts in north pacific climate variability here we present an extended tree ring record of january september goa coastal surface air temperatures using tree ring width data from coniferous trees growing in the mountain ranges along the goa the reconstruction 1514 1999 based on living trees ex plains 44 of the temperature variance although as the number of chronologies decreases back in time this value decreases to and remains around 30 before 1840 verification of the calibrated models is however robust utilizing sub fossil wood we extend the goa reconstruction back to the early eighth century the goa reconstruction correlates significantly 95 cl with both the pacific decadal oscillation index 0 53 and north pacific index 0 42 and therefore likely yields important information on past climate variability in the north pacific region intervention analysis on the goa reconstruction identifies the known twentieth century climate shifts around the 1940s and 1970s al though the mid 1920s shift is only weakly expressed in the context of the full 1 300 years record the well studied 1976 shift is not unique multi taper method spectral analysis shows that the spectral properties of the living and sub fossil data are similar with both records showing significant 95 cl spectral peaks at 9 11 13 14 and 18 19 years singular spectrum analysis identifies in order of importance significant oscillatory modes at 18 7 50 4 38 0 91 8 24 4 15 3 and 14 1 years the amplitude of these modes varies through time it has been suggested minobe in geo phys res lett 26 855 858 1999 that the regime shifts during the twentieth century can be explained by the interaction between pentadecadal 50 4 years and bi decadal 18 7 years oscillatory modes removal of these two modes of variance from our goa time series does indeed remove the twentieth century shifts but many are still identified prior to the twentieth century our analysis suggests that climate variability of the goa is very complex and that much more work is required to understand the underlying oscillatory behavior that is observed in instrumental and proxy records from the north pacific region

seismic energy partitioning and scattering in laterally heterogeneous ocean crust we present finite difference forward models of elastic wave propagation through laterally heterogeneous upper oceanic crust the finite difference formulation is a 2 d solution to the elastic wave equation for heterogeneous media and implicitly calculates p and sv propagation compressional to shear conversion interference effects and interface phenomena random velocity perturbations with gaussian and self similar autocorrelation functions and different correlation lengths a are presented which show different characteristics of secondary scattering heterogeneities scatter primary energy into secondary body waves and secondary stoneley waves along the water solid interface the presence of a water solid interface in the model allows for the existence of secondary stoneley waves which account for much of the seafloor noise seen in the synthetic seismograms for the laterally heterogeneous models

a six hundred year annual minimum temperature history for the central tibetan plateau derived from tree ring width series the recent unprecedented warming found in different regions has aroused much attention in the past years how temperature has really changed on the tibetan plateau tp remains unknown since very limited high resolution temperature series can be found over this region where large areas of snow and ice exist herein we develop two juniperus tibetica kom tree ring width chronologies from different elevations we found that the two tree ring series only share high frequency variability correlation response function and partial correlation analysis indicate that prior year annual january december minimum temperature is most responsible for the higher belt juniper radial growth while more or less precipitation signal is contained by the tree ring width chronology at the lower belt and is thus excluded from further analysis the tree growth climate model accounted for 40 of the total variance in actual temperature during the common period 1957 2010 the detected temperature signal is further robustly verified by other results consequently a six century long annual minimum temperature history was firstly recovered for the yushu region central tp interestingly the rapid warming trend during the past five decades is identified as a significant cold phase in the context of the past 600 years the recovered temperature series reflects low frequency variability consistent with other temperature reconstructions over the whole tp region furthermore the present recovered temperature series is associated with the asian monsoon strength on decadal to multidecadal scales over the past 600 years

underlying causes for long term global ocean δ13c fluctuations over the last 1 20 myr pleistocene stable carbon isotope 13c records from surface and deep dwelling foraminifera in all major ocean basins show two distinct long term carbon isotope fluctuations since 1 00 ma the first started around 1 00 ma and was characterised by a 0 35 decrease in 13c values until 0 90 ma followed by an increase of 0 60 lasting until 0 50 ma the subsequent fluctuation started with a 0 40 decrease between 0 50 and 0 25 ma followed by an increase of 0 30 between 0 25 and 0 10 ma here we evaluate existing evidence and various hypotheses for these global pleistocene 13c fluctuations and present an interpretation where the fluctuations most likely resulted from concomitant changes in the burial fluxes of organic and inorganic carbon due to ventilation changes and or changes in the production and export ratio our model indicates that to satisfy the long term stability of the pleistocene lysocline the ratio between the amounts of change in the organic and inorganic carbon burial fluxes would have to be close to a 1 1 ratio as deviations from this ratio would lead to sizable variations in the depth of the lysocline it is then apparent that the mid pleistocene climate transition which apart from the glacial cycles represents the most fundamental change in the pleistocene climate was likely not associated with a fundamental change in atmospheric pco2 while recognising that high frequency glacial interglacial cycles are associated with relatively large 100 ppmv changes in pco2 our model scenario with burial changes close to a 1 1 ratio produces a maximum long term variability of only 20 ppmv over the fluctuation between 1 00 and 0 50 ma

how stable are twentieth century calibration models a high resolution summer temperature reconstruction for the eastern swiss alps back to ad 1580 derived from proglacial varved sediments we found a significant positive correlation between local summer air temperature may september and the annual sediment mass accumulation rate mar in lake silvaplana 46 n 9 e 1800 m a s l during the twentieth century r 0 69 p 0 001 for decadal smoothed series sediment trap data 2001 2005 confirm this relation with exceptionally high particle yields during the hottest summer of the last 140 years in 2003 on this base we developed a decadal scale summer temperature reconstruction back to ad 1580 surprisingly the comparison of our reconstruction with two other independent regional summer temperature reconstructions based on tree rings and documentary data revealed a significant negative correlation for the pre 1900 data ie late little ice age this demonstrates that the correlation between mar and summer temperature is not stable in time and the actualistic principle does not apply in this case we suggest that different climatic regimes modern little ice age lead to changing state conditions in the catchment and thus to considerably different sediment transport mechanisms therefore we calibrated our mar data with gridded early instrumental temperature series from ad 1760 1880 r 0 48 p 0 01 for decadal smoothed series to properly reconstruct the late lia climatic conditions we found exceptionally low temperatures between ad 1580 and 1610 0 75 c below twentieth century mean and during the late maunder minimum from ad 1680 to 1710 0 5 c below twentieth century mean in general summer temperatures did not experience major negative departures from the twentieth century mean during the late little ice age this compares well with the two existing independent regional reconstructions suggesting that the lia in the alps was mainly a phenomenon of the cold season

annually resolved southern hemisphere volcanic history from two antarctic ice cores the continuous sulfate analysis of two antarctic ice cores one from the antarctic peninsula region and one from west antarctica provides an annually resolved proxy history of southern semisphere volcanism since early in the 15th century the dating is accurate within 3 years due to the high rate of snow accumulation at both core sites and the small sample sizes used for analysis the two sulfate records are consistent with each other a systematic and objective method of separating outstanding sulfate events from the background sulfate flux is proposed and used to identify all volcanic signals the resulting volcanic chronology covering 1417 1989 a d resolves temporal ambiguities about several recently discovered events a number of previously unknown moderate eruptions during late 1600s are uncovered in this chronology the eruption of tambora 1815 and the recently discovered eruption of kuwae 1453 in the tropical south pacific injected the greatest amount of sulfur dioxide into the southern hemisphere stratosphere during the last half millennium a technique for comparing the magnitude of volcanic events preserved within different ice cores is developed using normalized sulfate flux for the same eruptions the variability of the volcanic sulfate flux between the cores is within 20 of the sulfate flux from the tambora eruption

fennoscandian summers from ad 500 temperature changes on short and long timescales quantitative estimates of 1480 years of summer temperatures in northern fennoscandia have previously been derived from continuous treering records from northern sweden here we show the results of spectral analyses of these data only a few peaks in the spectra are consistently significant when the data are analyzed over a number of sub periods relatively timestable peaks are apparent at periods of 2 1 2 5 3 1 3 6 4 8 32 33 and for a range between 55 100 years these results offer no strong evidence for solar related forcing of summer temperatures in these regions our previously published reconstruction was limited in its ability to represent long timescale temperature change because of the method used to standardize the original tree ring data here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales considerable variance is now reconstructed on timescales of several centuries in comparison with modern normals 1951 70 generally extended periods when cool conditions prevailed prior to the start of the instrumental record include 500 700 790 870 1110 1150 1190 1360 1570 1750 a d with the most significant cold troughs centred on about 660 800 1140 1580 1620 and 1640 predominantly warm conditions occurred in 720 790 870 1110 and 1360 1570 with peaks of warmth around 750 930 990 1060 1090 1160 1410 1430 1760 and 1820

coupled productivity and carbon isotope records in the southwest pacific ocean during the late miocene early pliocene biogenic bloom biogenic components of sediment accumulated at high rates beneath frontal zones of the indian and pacific oceans during the late miocene and early pliocene the 13c of bulk and foraminiferal carbonate also decreased during this time interval although the two observations may be causally linked and signify a major perturbation in global biogeochemical cycling no site beneath a frontal zone has independent records of export production and 13c on multiple carbonate phases across the critical interval of interest deep sea drilling project dsdp site 590 lies beneath the tasman front tf an eddy generating jetstream in the southwest pacific ocean to complement previous 13c records of planktic and benthic foraminifera at this location late neogene records of caco3 mass accumulation rate mar ca ti ba ti al ti and of bulk carbonate and foraminiferal 13c were constructed at site 590 the 13c records include bulk sediment bulk sediment fractions 63 m and 5 25 m and the planktic foraminifera globigerina bulloides globigerinoides sacculifer with and without sac and orbulina universa using current time scales caco3 mars ca ti al ti and ba ti ratios are two to three times higher in upper miocene and lower pliocene sediment relative to overlying and underlying units a significant decrease also occurs in all 13c records all evidence indicates that enhanced export production the biogenic bloom extended to the southwest pacific ocean between ca 9 and 3 8 ma and this phenomenon is coupled with changes in 13c the chron c3ar carbon shift however caco3 mars peak ca 5 ma whereas elemental ratios are highest ca 6 5 ma foraminiferal 13c starts to decrease ca 8 ma whereas bulk carbonate 13c begins to drop ca 5 6 ma temporal discrepancies between the records can be explained by changes in the upwelling regime at the tf perhaps signifying a link between changes in ocean atmosphere circulation change and widespread primary productivity

lateglacial environmental variability from swiss tree rings abstract evidence of annually resolved environmental variations during the allerod interstadial is presented using 81 fossil scots pine tree ring series from gaenziloo and landikon near zurich switzerland the absolute age of the trees ranges between 11 920 and 10 610 14 c bp which was determined by wiggle matching radiocarbon ages to the cariaco 14 c data set from the two sites we created a composite floating allerod chronology on the basis of their 632 years of overlap r 0 57 after individual spline detrending merging both data sets resulted in a lateglacial tree ring chronology covering 1050 years regional curve standardization rcs was applied to preserve low frequency information growth behavior of the fossil trees was compared with a recent composite pine data set from the central swiss alps and reveals distinct differences the new allerod rcs chronology reveals major lateglacial variations such as the gerzensee oscillation the abrupt climate shift towards the younger dryas and some short term events radiocarbon ages agree well with those from other sites on the swiss plateau for hemispheric comparisons we used the annual layer thickness record from the ngrip ice core and the gray scale varve record from the cariaco basin even though the amplitudes are not yet fully understood similarities on decadal to centennial scales are apparent

constraints on the structure of the east pacific rise from seismic refraction data university of washington seismic data taken during rose phase 1 have been used to study the structure of the east pacific rise in the vicinity of 12 n off axis but within 50 km of the axis we find that the oceanic crust can be modeled with a rapid change in velocity in the top 2 5 km a zone of low but uniform velocity gradient from 2 5 to about 5 5 km and a transitional zone about 1 km thick to mantle material there is also evidence for substantial anisotropy in mantle velocity gradients with a positive velocity gradient in the spreading direction and a negative velocity gradient parallel to the rise under the rise axis the data allow at most a very narrow zone of low velocity less than about 2 km wide in the crust

reassessing the evidence for tree growth and inferred temperature change during the common era in yamalia northwest siberia the development of research into the history of tree growth and inferred summer temperature changes in yamalia spanning the last 2000 years is reviewed one focus is the evolving production of tree ring width trw and tree ring maximum latewood density mxd larch larix sibirica chronologies incorporating different applications of regional curve standardisation rcs another focus is the comparison of independent data representing past tree growth in adjacent yamalia areas yamal and polar urals and the examination of the evidence for common growth behaviour at different timescales the sample data we use are far more numerous and cover a longer time span at yamal compared to the polar urals but yamal has only trw while there are both trw and mxd for the polar urals we use more data sub fossil and from living trees than in previous dendroclimatic studies in this region we develop a new trw chronology for yamal more than 2000 years long and running up to 2005 for the polar urals we develop new trw and mxd chronologies that show good agreement at short 15 years and medium 15e100 years timescales demonstrating the validity of attempts to reconcile the evidence of longer timescale information that they provide we use a conservative application of the rcs approach two curve signal free rcs guarding against the possibility of modern sample bias a possible inflation of recent chronology values arising out of inadvertent selection of mostly relatively fast growing trees in recent centuries we also transform tree indices to have a normal distribution to remove the positive chronology skew often apparent in rcs trw chronologies this also reduces the apparent magnitude of 20th century tree growth levels thereis generallygoodagreement between all chronologies as regardsthe major featuresof the decadal to centennial variability low tree growth periods for which the inferred summer temperatures are approximately 2 5 c below the 1961e90 reference are apparent in the 15 year smoothed reconstructions

a 9111 year long conifer tree ring chronology for the european alps a base for environmental and climatic investigations an ultra long tree ring width chronology 9111 years long 7109 bc to ad 2002 has been established based on the analysis and dating of 1432 subfossil dry dead wood samples and cores from 335 living trees the material was collected from treeline or near treeline sites c 2000 to 2400 m a s l mainly in the eastern alps the availability of preserved samples through time at high altitudinal sites is influenced by alpine forest history and is partly climatically controlled as shown by comparisons of the sample depth record of the eastern alpine conifer chronology eacc with the holocene glacier record the similarity of variations over time between the sample depth of the chronology and the mid holocene gisp2 10be record suggest a relationship between sample depth and solar activity the eastern alpine conifer chronology has already been used as a dating base in environmental studies eg on glacier fluctuations as well as in archaeological studies

a ring width based reconstruction of june july minimum temperatures since ad 1245 from white spruce stands in the mackenzie delta region northwestern canada abstract we present a reconstruction of june july minimum temperatures since ad 1245 for the mackenzie delta region based on a 29 site network of white spruce picea glauca ring width series most but not all trees experienced a divergent temperature growth response similar to the divergence that has affected other white spruce trees across yukon and alaska however divergence in the study region began as early as ad 1900 and we have documented our methods to avoid including divergent signals in the reconstruction calibration verification testing based on local temperature data and multi century coherence with nearby and large scale temperature proxy records confirm that our reconstruction is robust the reconstruction shows cool conditions in the late 13th early 18th and early 19th centuries corresponding with solar minima and increased volcanism these cool periods are interrupted by warm periods consistent with early to mid 20th century warmth the late 20th century is the warmest interval and the last decade is estimated to be 1 4 c warmer than any decade before the mid 20th century the reconstructed climate history corroborates other proxy based inferences and supports the notion that high latitude regions such as the mackenzie delta have experienced rapid warming in recent decades that is exceptional in the last eight centuries

methods to merge overlapping tree ring isotope series to generate multi centennial chronologies abstract stable isotopes ratios in tree rings are increasingly used to assess long term environmental variation as with conventional tree ring investigations crossdating overlapping sequences of wood material allows chronologies longer than the lifespans of individual trees to be developed we measured data from four overlapping cohorts of recent ad 1650 2004 and historic ad 1100 1198 ad 1150 1325 ad 1256 1700 wood to yield millennial length 13 c d and 18 o chronologies however we found that offsets in absolute isotopic values between overlapping segments challenge the preservation of low frequency climate signals in this paper we describe the development of these records signal strength assessments and present the problems associated with overcoming these offsets and preserving low frequency variance we then propose and evaluate four different solutions to link the cohorts these methods include various types of transformations of mean and variance all present potential advantages and drawbacks inflated variance loss of absolute isotope values and the loss of low frequency signals are major problems only one method is capable of fully preserving low frequency trends but this method may also risk inducing long term artifacts while the various solutions we propose may be useful to help overcome such biases the challenges described here if typical for other isotopic series will best be solved by additionally modifying sampling and measurement procedures we recommend avoiding pooling of tree rings in the overlap period and to increase the replication in order to extract the original signal and to maintain low frequency signals

reconstructing holocene climate from tree rings the potential for a long chronology from the scottish highlands despite promising research in the 1980s showing the potential of scots pine pinus sylvestris l for the reconstruction of past summer temperatures in the scottish highlands little dendroclimatic work has been attempted in this region since this reflects in part the limited number of sparsely distributed remnant natural semi natural pine woodlands in the scottish highlands and the lack of old growth forest therein on average most of the pine trees dated in this region are around 225 years in age here we present the first results of an ongoing interdisciplinary initiative to develop a long scottish chronology through the acquisition of modern historical and subfossil pine material from the native pinewoods historic structures and lakes of the scottish highlands radiocarbon dating of 25 subfossil pine timbers recovered from lake sediments identified the presence of preserved material covering the last 8000 years with initial clusters focused on the last two millennia and early mid holocene alth

reconstructing 800 years of summer temperatures in scotland from tree rings this study presents a summer temperature reconstruction using scots pine tree ring chronologies for scotland allowing the placement of current regional temperature changes in a longer term context living tree chronologies were extended using subfossil samples extracted from nearshore lake sediments resulting in a composite chronology 800 years in length the north cairngorms ncairn reconstruction was developed from a set of composite blue intensity high pass and ring width low pass filtered chronologies with a range of detrending and disturbance correction procedures calibration against july august mean temperature explains 56 4 of the instrumental data variance over 1866 2009 and is well verified spatial correlations reveal strong coherence with temperatures over the british isles parts of western europe southern scandinavia and northern parts of the iberian peninsula ncairn suggests that the recent summer time warming in scotland is likely not unique when compared to multi decadal warm periods observed in the 1300s 1500s and 1730s although trends before the mid sixteenth century should be interpreted with some caution due to greater uncertainty prominent cold periods were identified from the sixteenth century until the early 1800s agreeing with the so called little ice age observed in other tree ring reconstructions from europe with the 1690s identified as the coldest decade in the record the reconstruction shows a significant cooling response 1 year following volcanic eruptions although this result is sensitive to the datasets used to identify such events in fact the extreme cold and warm years observed in ncairn appear more related to internal forcing of the summer north atlantic oscillation

atmospheric circulation variability in the north atlantic european area since the mid seventeenth century based on monthly mean sea level pressure grids objectively reconstructed by luterbacher et al variations of dynamical modes of the atmospheric circulation for january and july are described by novel indices for running 31 year periods between 1659 and 1999 these indices reflect the continuous evolution of the atmospheric circulation not only with regard to frequency changes of major dynamical modes but also in terms of internal changes within each mode concerning both dynamic vorticity intensity and climatic properties central european temperature and precipitation during occurrence of each mode respectively results indicate the great importance of within mode variations the zonal circulation mode in january varying in frequency with long term cycles primarily changed its dynamic and climatic properties towards higher indices during the transition from the little ice age to modern conditions between 1800 and 1930 within the russian high mode of january a change in preference from easterly to westerly patterns above central europe occurred around 1850 for july a striking frequency maximum of the westerly mode at the end of the eighteenth century coincided with a period of marked summer warmth in central europe due to negative positive deviations in vorticity temperature during occurrence of this mode the long term evolution in july indicates a general increase of anticyclonic conditions strengthening during the last 50 years towards a unique phenomenon within the last centuries the strong increase in the winter time westerly circulation during the last decades however does not appear extraordinary in view of the low frequency variations of this mode

on smoothing potentially non stationary climate time series 1 a simple approach to the smoothing of a potentially non stationary time series is presented which provides an optimal choice among three alternative readily motivated and easily implemented boundary constraints this method is applied to the smoothing of the instrumental northern hemisphere nh annual mean and cold season north atlantic oscillation nao time series yielding an objective estimate of the smoothed decadal scale variations in these series including long term trends

tree ring recorded may august temperature variations since a d 1585 in the gaoligong mountains southeastern tibetan plateau abstract high resolution proxy data are still scarce in the southeastern tibetan plateau which limit our understanding of climatic variability before instrumental records in this study we developed 595 year tree ring width chronology from larix speciosa near the timberlines of the gaoligong mountains southeastern tibetan plateau ring width site chronologies and a well replicated regional chronology rc showed significant positive correlations with warm season temperatures from may to august using rc as predictor we reconstructed mean may august temperature for the study region that extends back to a d 1585 cold conditions prevailed during the periods 1600s 1620 30 1640 50s 1700s 1730 40s 1760s 1810 20s 1850s 1900 10s and 1955 70 warm episodes occurred during 1610s 1660 1680s 1710 20s 1750s 1780 90s 1820 40 1920 50 and 1980 present spatial correlations with gridded land surface temperatures revealed that our reconstruction represents regional temperature signal for the southern tibetan plateau comparison with other tree ring based temperature reconstructions from surrounding areas implies a high degree of confidence for our reconstruction

broad region of no sediment in the southwest pacific basin a broad region nearly the size of the mediterranean sea exists in the central south pacific ocean that is devoid of sediment and has been so since the late cretaceous the requirements for remaining sediment free are very low biological productivity a shallow calcite compensation depth essentially no dust input and no deposition of hydrothermal oxides and hydroxides one or two of these conditions are common but nowhere else do all four occur the combined effect of these sediment inhibiting factors is a consequence of crustal age seawater chemistry and atmospheric oceanographic and physiographic isolation furthermore this unique combination of conditions has prevailed for more than 80 million years

pacific caco3 preservation and δ18o since 4 ma paleoceanic and paleoclimatic implications the pliocene pleistocene history of caco3 preservation in the central equatorial pacific is reconstructed from a suite of deep sea cores and is compared to fluctuations in global ice volume inferred from 18o records the results are highlighted by 1 a strong covariation between caco3 preservation and ice volume over 104 to 106 year time scales 2 a long term increase in ice volume and caco3 preservation since 3 9 ma demonstrated by a deepening of the lysocline and the carbonate critical depth 3 a dramatic shift to greater caco3 preservation at 2 9 ma 4 distinctive ice volume growth and caco3 preservation events at 2 4 ma which are associated with the significant intensification of northern hemisphere glaciation 5 a mid pleistocene transition to 100 kyr cyclicity in both caco3 preservation and ice volume and 6 a 600 kyr brunhes dissolution cycle superimposed on the late pleistocene glacial interglacial 100 kyr cycles caco3 preservation primarily reflects the carbonate chemistry of abyssal waters and is controlled by long term 106 year and short term 104 to 105 year biogeochemical cycling and by distinct paleoclimatic events we attribute the long term increase in caco3 preservation primarily to a fractionation of caco3 deposition from continental shelf to ocean basin and secondarily to a gradual rise in the riverine and glaciofluvial flux of ca on shorter time scales the fluctuations in caco3 preservation slightly lag ice volume fluctuations and are attributed to climatically induced changes in the circulation and chemistry of pacific deep water

holocene temperature variations at a high altitude site in the eastern alps a chironomid record from schwarzsee ob solden austria few well dated quantitative holocene temperature reconstructions exist from high altitude sites in the central eastern alps here we present a chironomid based quantitative reconstruction of mean july air temperatures tjuly throughout the holocene for a remote high mountain lake schwarzsee ob solden situated above the treeline at 2796 m a s l in the austrian alps applying a chironomid temperature inference model developed from lakes of the alpine region to a high resolution chironomid record from the lake provides evidence for early holocene ca 10000 8600 cal yr bp tjuly of up to 8 5 c i e 4 c above the modern 1977 2006 mean july temperature the reconstruction reveals the so called 8 2 ka cold event centered at ca 8250 8000 cal yr bp with temperatures ca 3 c below the early holocene thermal maximum rather warm ca 6 c and productive conditions prevailed during ca 7900 4500 cal yr bp the chironomid record suggests a climate transition between ca 5200 and 4500 cal yr bp to cooler tjuly a distinct cooling trend is evident from ca 4500 until ca 2500 cal yr bp thereafter the study site experienced its coldest conditions around 4 c or less throughout the rest of the holocene with the exception of the warming trend during the late 20th century beside other factors the northern hemisphere summer insolation seems to be the major driving force for the long term trends in tjuly at high altitudes in the eastern alps due to the extreme location of the lake and the limited temperature range represented by the applied calibration data set the chironomid based temperature reconstruction fails to track phases of the late holocene climatic history with tjuly cooler than 4 c further chironomid based palaeoclimate model and down core studies are required to address this problem provide more realistic tjuly estimates from undisturbed high altitude lakes in the alps and extract a reliable regional temperature signal

persistent influence of the north atlantic hydrography on central european winter temperature during the last 9000 years 1 a prominent feature of the n atlantic s holocene climate is a series of centennial and millennial shifts in ocean surface hydrography bond et al 2001 oppo et al 2003 here we compare a climate reconstruction from the central alps for the last 9 000 years derived from the oxygen isotope record in stalagmites with the percentage of hematite stained grains in n atlantic sediments an indicator for the proportion of ice bearing surface water from north of iceland the excellent match between the two curves proves that meteorological conditions in the alpine region responded synchronously to changes in the hydrography of the n atlantic during winter in addition the speleothem record suggests significant multi centennial and millennial variability of n european winters throughout the past 9 000 years that might have been incompletely recorded in tree ring archives

miocene stable isotope record a detailed deep pacific ocean study and its paleoclimatic implications deep sea drilling project site 289 in the western equatorial pacific has yielded an extremely detailed record of the carbon and oxygen isotopic changes in the miocene deep ocean the isotopic record reflects major changes in paleoclimate and paleoceanography probably dominated by a major phase of antarctic ice cap growth the transition from a relatively unglaciated world to one similar to today occurred between 16 5 x 10 6 and 13 x 10 6 years before the present with the greatest change occurring between approximately 14 8 x 10 6 and 14 0 x 10 6 years before the present

high resolution chironomid inferred temperature history since ad 1580 from varved lake silvaplana switzerland comparison with local and regional reconstructions chironomids were used to reconstruct mean july air temperatures between c ad 1580 and 2001 at lake silvaplana a varved lake located in the engadine eastern swiss alps the goal of this study was to reconstruct temperature changes at near annual resolution and validate the reconstruction by comparison with records based on early instrumental data documentary proxy evidence dendrochronology geochemical biogenic silica bsi and mineralogical data quartz mica ratios at local and regional scales warmer than the climate normal ad 1961 1990 mean july air temperatures were inferred between c ad 1610 and 1662 ad 1710 and 1740 ad 1790 and 1866 ad 1940 and 1960 and ad 1990 and 2001 colder than the climate normal july air temperatures were reconstructed between c ad 1662 and 1710 ad 1740 and 1790 ad 1866 and 1919 and ad 1970 and 1990 the 420 year chironomid inferred mean july air temperature record was significantly p 0 01 related to june september jjas temperatures reconstructed from e

two major cenozoic episodes of phosphogenesis recorded in equatorial pacific seamount deposits seamount phosphorites have been recognized since the 1950s but this is the first study to provide an in depth exploration of the origin and history of these widespread deposits representative samples from equatorial pacific cretaceous seamounts were analyzed for chemical mineralogical and stable isotope compositions the phosphorites occur in a wide variety of forms but most commonly carbonate fluorapatite cfa replaced middle eocene and older carbonate sediment in a deep water environment 1000 m element ratios distinguish seamount phosphorites from continental margin plateau and insular phosphorites uranium and thorium contents are low and total rare earth element ree contents are generally high ree ratios and shale normalized patterns demonstrate that the rees and host cfa were derived from seawater strontium isotopic compositions compared with inferred cenozoic seawater curves define two major episodes of cenozoic phosphatization late eocene early oligocene 39 34 ma and late oligocene early miocene 27 21 ma three minor events are also indicated the major episodes occurred at times of climate transition the first from a nonglacial to glacial earth and the second from a predominantly glacial to warm earth the paleoceanographic conditions that existed at those times initiated and sustained development of phosphorite by accumulation of dissolved phosphorus in the deep sea during relatively stable climatic conditions when oceanic circulation was sluggish fluctuations in climate sealevel and upwelling that accompanied the climate transitions may have driven cycles of enrichment and depletion of the deep sea phosphorus reservoir as temperature gradients in the oceans increased antarctic glaciation expanded and oceanic circulation and upwelling intensified expansion and intensification of the oxygen minimum zone may have increased the capacity for midwater storage of phosphorus supplied by dynamic upwelling around seamounts however the bottom waters never became anoxic during the phosphogenic episodes fluctuations in the ccd and lysocline co2 fluxes and changes in bottom water circulation and temperatures may have bathed the seamount carbonates in more corrosive waters which coupled with increased supplies of dissolved phosphorus promoted replacement processes the late eocene early oligocene phosphogenic episode recorded in seamount deposits is not matched by large phosphorite deposits in the geologic record whereas the late oligocene early miocene episode and middle miocene event are matched by large deposits distributed globally the seamount phosphorites are exposed at the surface of the seamounts and have been for most of the neogene and oligocene the phosphorites do not show signs of etching that would indicate substantial undersaturation of seawater phosphate with respect to cfa mass balance calculations indicate that about 5 4 19 1012 g of p2o5 are locked up in equatorial pacific seamount phosphorites that amount is equivalent to about 2 7 years of the present annual input from rivers

tree ring width and density data around the northern hemisphere part 2 spatio temporal variability and associated climate patterns patterns of summer temperature over the northern hemisphere obtained from a calibration of a treering network are presented for every year from 1600 to 1877 the network of tree ring density chronologies is shown to exhibit spatially coherent modes of variability these modes closely match summer half year tempera ture variations in terms of similar spatial patterns and similar temporal evolution during the instrumental period they can therefore be considered to be proxies for the temperature patterns and time series for the eight most dominant patterns are presented back to the late seventeenth century the first pattern represents spatially coherent warming or cooling and it appears to respond to climate forcings especially volcanic erup tions most other patterns appear to be related to atmospheric pressure anomalies and they can be partially explained by heat advection associated with anomalous atmospheric circulation this provides the potential for reconstructing past variations in atmospher

oceanic ridge crest processes oceanic ridge crest processes constitute a vigorous frontier of multidisciplinary research with global ramifications in the earth atmospheric and biologic sciences this deep ocean frontier is gradually opening in response to investigations which are elucidating the role of these processes in the lithosphere hydrosphere atmosphere and biosphere and the application of advanced instrumental and interpretive techniques which are increasing the quality and quantity of data these techniques include crustal drilling with borehole logging deep sea drilling project reports high resolution bathymetry sea beam etc side scan sonar seamarc i and ii gloria etc imagery with video and photography multichannel seismics determination of water column properties ctd with rosette sampler etc and submersible applications

a composite sea surface temperature record of the northern south china sea for the past 2500 years a unique look into seasonality and seasonal climate changes during warm and cold periods abstract high resolution late holocene climate records that can resolve seasonality are essential for confirming past climatic dynamics understanding the late 20th century global warming and predicting future climate here a new composite record of the sea surface temperature sst variation in the northern south china sea scs during the late holocene is constructed by combining seven seasonally resolved coral and tridacna gigas sr ca based sst time windows with the instrumental sst record from modern interval between 1990 and 2000 this composite multi proxy marine record together with the reconstructions from mainland china and tropical western pacific indicates that the late holocene warm periods the roman warm period rwp and medieval warm period mwp were prominently imprinted and documented in the climatic and environmental history of the east asia western pacific region meanwhile substantial and significant sst seasonality variations during the late holocene were observed in the composite record the observed increase in seasonality or amplitude of seasonal cycles during the cold periods around our study area was probably caused by the different amplitudes between winter versus summer sst variations in northern scs with much larger sst variation during winters than during summers for the late holocene in addition the distinctive warm cold and neutral climatic episodes identified in our northern scs composite sst record correspond well with other paleo reconstructions from mainland china and especially well with the northern hemisphere wide composites by moberg et al 2005 and ljungqvist 2010 the overall agreement however also calls for more information and insights on how seasonal temperatures and their ranges vary on decadal centennial timescales

quantitative estimates of temperature and precipitation changes over the last millennium from pollen and lake level data at lake joux swiss jura mountains abstract this paper presents quantitative climate estimates for the last millennium using a multi proxy approach with pollen and lake level data from lake joux swiss jura mountains the climate reconstruction based on the modern analogue technique indicates warmer and drier conditions during the medieval warm period mwp mwp was preceded by a short lived cold humid event around ad 1060 and followed by a rapid return around ad 1400 to cooler and wetter conditions which generally characterize the little ice age lia around ad 1450 solar sporer minimum the lia attained a temperature minimum and a summer precipitation maximum the solar maunder minimum around ad 1690 corresponded at joux to rather mild temperatures but maximal annual precipitation these results generally agree with other records from neighbouring alpine regions however there are differences in the timing of the lia temperature minimum depending on the proxy and or the method used for the reconstruction as a working hypothesis the hydrological signal associated with the mwp and lia oscillations at lake joux may have been mainly driven by a shift around ad 1400 from positive to negative nao modes in response to variations in solar irradiance possibly coupled with changes in the atlantic meridional overturning circulation

temperature covariance in tree ring reconstructions and model simulations over the past millennium spatial covariance in the simulated temperature evolution over the past millennium has been reported to exceed that of multiproxy based reconstructions here we use tree ring based temperature reco

marine climate in the irish sea analysis of a 489 year marine master chronology derived from growth increments in the shell of the clam arctica islandica abstract we demonstrate here that the growth increment variability in the shell of the long lived bivalve mollusc arctica islandica can be interpreted as an indicator of marine environmental change in the climatically important north atlantic shelf seas multi centennial up to 489 year chronologies were constructed using five detrending techniques and their characteristics compared the strength of the common environmental signal expressed in the chronologies was found to be fully comparable with equivalent statistics for tree ring chronologies the negative exponential function using truncated increment width series from which the first thirty years have been removed was chosen as the optimal detrending technique chronology indices were compared with the central england temperature record and with seawater temperature records from stations close to the study site in the irish sea statistically significant correlations were found between the chronology indices and a mean air temperature for the 14 month period beginning in the january preceding the year of growth b mean seawater temperatures for february october in the year preceding the year of growth c late summer and autumn air temperatures and sea surface temperatures for the year of growth and d the timing of the autumn decline in sst changes through time in the correlations with air and seawater temperatures and changes towards a deeper water origin for the shells in the chronology were interpreted as an indication that shell growth may respond to stratification dynamics

summer temperatures in the canadian rockies during the last millennium a revised record we present a significant update to a millennial summer temperature reconstruction 1073 1983 that was originally published in 1997 utilising new tree ring data predominantly picea engelmannii the reconstruction is not only better replicated but has been extended 950 1994 and is now more regionally representative calibration and verification statistics were improved with the new model explaining 53 of may august maximum temperature variation compared to the original 39 of april august mean temperatures the maximum latewood density data which are weighted more strongly in the regression model than ringwidth were processed using regional curve standardisation to capture potential centennial to millennial scale variability the reconstruction shows warm intervals comparable to twentieth century values for the first half of the eleventh century the late 1300s and early 1400s the bulk of the record however is below the 1901 1980 normals with prolonged cool periods from 1200 to 1350 and from 1450 to the late 19th century the most extreme cool period is observed to be in the 1690s these reconstructed cool periods compare well with known regional records of glacier advances between 1150 and the 1300s possibly in the early 1500s early 1700s and 1800s evidence is also presented of the influence of solar activity and volcanic events on summer temperature in the canadian rockies over the last 1 000 years although this reconstruction is regional in scope it compares well at multi decadal to centennial scales with northern hemisphere temperature proxies and at millennial scales with reconstructions that were also processed to capture longer timescale variability this coherence suggests that this series is globally important for the assessment of natural temperature variability over the last 1 000 years

a review of climate reconstructions from terrestrial climate archives covering the first millennium ad in northwestern europe large changes in landscape vegetation and culture in northwestern nw europe during the first millennium ad seem concurrent with climatic shifts understanding of this relation requires high resolution palaeoclimate reconstructions therefore we compiled available climate reconstructions from sites across nw europe extent research area 10 w 20 e 45 60 n through review of literature and the underlying data to identify supraregional climatic changes in this region all reconstructions cover the period from ad 1 to 1000 and have a temporal resolution of 50 yr this resulted in 22 climate reconstructions proxy records based on different palaeoclimate archives chironomids 1 pollen 6 sphagnum mosses 1 stalagmites 8 testate amoebae 4 and tree rings 2 comparing all temperature reconstructions we conclude that summer temperatures between ad 1 and 250 were relatively high and the period between ad 250 and 700 was characterised by colder summer conditions the period from ad 700 to 1000 was again characterised by warmer summers these temperature shifts occurred in the whole of nw europe in contrast the compilation of precipitation reconstructions does not show a common pattern across nw europe either as a result of a heterogeneous precipitation pattern or the lack of suitable and consistent precipitation proxies

climate signals in tree ring width density and δ13c from larches in eastern siberia russia abstract we present the first and longest 413 years dataset on stable carbon isotope ratios in tree ring cellulose 13c tree ring width trw and maximum latewood density mxd obtained from larch trees growing on permafrost under continental climate in the suntar khayata mountain ridge in eastern siberia russia with this first study we calibrate tree ring parameters against climate quantities and based on these results assess the potential added value of mxd and especially of 13c complementing trw analysis for future climate reconstruction purposes 13c chronologies were corrected for human induced changes in atmospheric co2 since ad 1800 two different approaches were compared i a correction referring merely to the decline in atmospheric 13c 13catm and ii a correction additionally accounting for the increase in atmospheric partial pressure of co2 13c chronologies are characterized by strong signal strength with only 4 trees representing the population signal at the site mean inter series correlation 0 71 and eps 0 90 13c variation shows low similarity to trw and mxd while correlation between trw and mxd is highly significant correlation analysis of tree ring parameters with gridded instrumental data climate research unit cru ts 2 1 over the ad 1929 2000 calibration period demonstrates that trw and mxd react as reported from other sites at cold and humid northern latitudes precipitation plays no significant role but strong dependencies on monthly mean maximum and minimum temperatures particularly of the current summer june to august are found up to r 0 60 p

an investigation of the common signal in tree ring stable isotope chronologies at temperate sites we observed a strong common high frequency interannual signal for thed 13 c chronologies whereas the low frequency decadal scale signal was more similar among thed 18 o chronologies for both carbon and oxygen isotopes we found significant positive relationships with annual and growing season temperatures and negative relationships with precipitation again of similar magnitude for all species except forfraxinus which contained only minor climatic information averaging of all chronologies resulted in an increase in the climatic signal of the mean chronology the combinedd 18 o record reflected decadal scale temperature variations remarkably well r 0 72 however the relationship between climate and carbon isotopes declined over the last 3 decades of the 20th century probably related to the steep increase in atmospheric co 2 concentrations resulting in strongly divergingd 13 c trends of the different chronologies our study indicates that combining chronologies from different species enhances the potential of isotope studies for extending climate reconstructions into areas of temperate climate

a precisely dated climate record for the last 9 kyr from three high alpine stalagmites spannagel cave austria 1 here we use the 18o time series of three stalagmites from the high alpine spannagel cave austria which grew in small distance from each other to construct a precisely dated continuous 18o curve for the last 9 kyr comnispa this speleothem record is not influenced by effects of kinetic isotope fractionation due to the low temperatures in the cave thus the variations in 18o can be interpreted in terms of past climate change comnispa exhibits several oscillations within the holocene and their timing and duration is in agreement with that documented by other alpine archives

long term summer temperature reconstruction inferred from tree ring records from the eastern carpathians the first 1 000 year long carpathian tree ring width chronology was established based on living and subfossil stone pine pinus cembra l samples from an upper timberline forest located in calimani mts romania tree ring data were standardized using the regional curve standardization method in order to preserve the low and medium frequency climate signals the de trended index strongly correlates with summer mean temperature both at annual and decadal scales the calimani summer mean temperature anomalies were reconstructed for the period ad 1163 2005 applying the rescaling method this new climate proxy from the carpathians shows similar fluctuations to other north hemispheric temperature reconstructions but with periods of distinct differences the fingerprint of little ice age in the calimani area is visible between ad 1370 and 1630 followed by lagged cold decades in ad 1820 and 1840 the recent warming is evident only after the 1980s in our reconstruction

potential origins of 400 500 kyr periodicities in the ocean carbon cycle a box model approach 1 cenozoic proxy records of both the isotopic composition of dissolved inorganic carbon in the oceans 13cdic and deep ocean carbonate preservation show significant periodicities in the range 400 500 kyr sensitivity analysis of the ocean carbon cycle to potential variability on this timescale in patterns of global oceanic primary productivity and or continental weathering fluxes is performed using a 7 box ocean atmosphere model the data constraints imposed by plio pleistocene proxy records of 13cdic carbonate preservation and atmospheric pco2 variability allow different scenarios to be evaluated forcing with the global oceanic primary production ratio of inorganic and organic carbon leads to the relative phases of response most consistent with the proxy data however only when changes also occur in total marine primary production can the observed relative amplitudes of 13cdic and pco2 variability also be reproduced this scenario is consistent with oscillations between a highly productive coccolithophore rich global ocean and a less productive diatom rich one such oscillations have been proposed to originate from the orbital eccentricity cycle leading to changes in seasonality and thus silica utilization in the southern ocean however the period of response in model 13cdic is always close to that of the forcing function used and thus a significant discrepancy remains between the orbital eccentricity cycle period of 413 kyr and the observed 500 kyr 13cdic periodicity seen in the pleistocene

a 500 year record of summer near ground solar radiation from tree ring stable carbon isotopes tree ring stable carbon isotope ratios d13c in environments of low moisture stress are likely to be controlled primarily by photosynthetic rate therefore sunshine rather than temperature represents the more direct controlling factor temperature reconstructions based on tree ring d13c results thus rest on the assumption that temperature and sunshine are strongly coupled this assumption is tested using a d13c series from pine trees in nw norway where there are long 100 yr records of both summer temperature and cloud cover it is demonstrated that when summer temperature and d13c diverge summer temperature and cloud cover also diverge and that cloud cover sunshine may provide a stronger and more consistent parameter with which to calibrate tree ring d13c series in this area when a 500 year reconstruction of summer cloudiness is compared with a published reconstruction of summer temperatures in northern sweden based on tree ring maximum densities the two time series are largely parallel with

temperature sensitive tien shan tree ring chronologies show multi centennial growth trends two millennia length juniper ring width chronologies processed to preserve multi centennial growth trends are presented for the alai range of the western tien shan in kirghizia the chronologies average the information from seven near timberline sampling sites and likely reflect summer temperature variation for comparison chronologies are also built using standard dendrochronological techniques we briefly discuss some qualities of these inter decadal records and show the low frequency components removed by the standardization process include a long term negative trend in the first half of the last millennium and a long term positive trend since about ad 1800 the multi centennial scale alai range chronologies where these trends are retained are both systematically biased but in an opposite sense in their low frequency domains nevertheless they represent the best constraints and estimates of long term summer temperature variation and reflect the medieval warm period the little ice age and a period of warming since about the middle of the nineteenth century

the little ice age signature in a 700 year high resolution chironomid record of summer temperatures in the central eastern alps despite the fact that the little ice age lia is well documented for the european alps substantial uncertainties concerning the regional spatio temporal patterns of temperature changes associated with the lia still exist especially for their eastern sector here we present a high resolution 4 10 years 700 year long mean july air temperature reconstruction based on subfossil chironomid assemblages from a remote lake in the austrian eastern alps to gain further insights into the lia climatic deterioration in the region the record provides evidence for a prolonged period of predominantly cooler conditions during ad 1530 1920 broadly equivalent to the climatically defined lia in europe the main lia phase appears to have consisted of two cold time intervals divided by slightly warmer episodes in the second half of the 1600s the most severe cooling occurred during the eighteenth century the lia temperature minimum about 1 5 c below the long term mean recorded in the mid 1780 s coincides with the strongest volcanic signal found in the greenland ice cores over the past 700 years and may be at least in part a manifestation of cooling that followed the long lasting ad 1783 1784 laki eruption a continuous warming trend is evident since ca ad 1890 1 1 c in 120 years the chironomid inferred temperatures show a clear correlation with the instrumental data and reveal a close agreement with paleotemperature evidence from regional high elevation tree ring chronologies a considerable amount of the variability in the temperature record may be linked to changes in the north atlantic oscillation

applications of stalagmite laminae to paleoclimate reconstructions comparison with dendrochronology climatology abstract laminated stalagmites observed in either ultra violet or visible light or recognized via trace elements are now widely recognized as a common deposition form annually laminated stalagmites should be expected in caves which have an overlying climate that has a strong seasonality similar climate zones to where trees grow with distinct annual rings continuous laminated stalagmite chronologies up to several thousand years should be expected where some mixing of stored water occurs such stalagmites can be used to reconstruct climate particularly through variations in lamina width such climate records would be relatively damped by mixing of event water with stored groundwater constraining the amount of high frequency climate signals contained in the stalagmite but relatively long continuous lamina sequences permit the preservation of low frequency centennial scale climate signals this contrasts with numerous tree ring climate records which are frequently limited in preserving multi centennial trends due to the necessary removal of age related noise from relatively short tree segments laminated stalagmites and tree rings should therefore to some degree provide complementary climate information appropriate methods for compiling stalagmite layer chronologies and climatologies are presented

thousand years of climate change reconstructed from chironomid subfossils preserved in varved lake silvaplana engadine switzerland abstract fossil chironomids non biting midges from varved lake silvaplana switzerland were used to reconstruct climate mean july air temperatures during the last millennium at the beginning of the record corresponding to the last part of the medieval climate anomaly mca here the period between ca 1032 and 1262 ad the chironomid inferred mean july air temperatures were 1 c warmer p

a review of finite difference methods for seismo acoustics problems at the seafloor understanding seismic wave propagation in realistic seafloor environments is essential for many problems in marine seismology finite difference methods are becoming increasingly popular in solving propagation problems as the limitations of other techniques which apply only at high frequency or for flat lying media become fully appreciated the seafloor problem a high contrast in poisson s ratio at a rough sharp interface is particularly challenging and many published formulations fail to solve it accurately the purpose of this paper is to summarize the published finite difference formulations for the elastic wave equation and to outline their applicability to seafloor problems

effect of scaling and regression on reconstructed temperature amplitude for the past millennium 1 examination of large scale millennial long temperature reconstructions reveals a wide range of datasets and methods used for calibration proxy time series are commonly calibrated against overlapping instrumental records representing different seasons northern hemisphere latitudinal bands and including or excluding sea surface temperature data methodological differences include using scaling or regression the calibration time period and smoothing data before calibration we find that these various approaches alone can result in differences in the reconstructed temperature amplitude of about 0 5 c this magnitude is equivalent to the mean annual temperature change for the northern hemisphere reported in the last ipcc report for the 1000 1998 period a more precise assessment of absolute reconstructed temperature amplitudes is necessary to help quantify the relative influences of forcing mechanisms in climate models

modeling cenozoic sedimentation in the central equatorial pacific and implications for true polar wander high productivity along the central pacific equator has left thick deposits of calcareous and siliceous ooze west of 102 w these have deposited on the pacific plate which has been drifting northwards and therefore the thickest deposits are displaced north of the equator this study attempts to simulate the sediment distribution using information from deep sea drilling project dsdp cores and models for pacific plate motion the dsdp core data are used to account for accumulation rate variations with time paleolatitude and paleodepth accounting for variable carbonate dissolution the model predicts the distribution on 35 50 ma seafloor relatively well and demonstrates that the sedimentary bulge is distorted by variable dissolution over a regional bathymetry gradient due to the northern edge of the south pacific superswell a westerly deepening of the carbonate compensation depth and sedimentary lysocline evolution are proposed which improve the model for seafloor 30 ma and older the degree of match between model and data provides a test of the amount of northward drift of the pacific plate and assuming a model for pacific hotspots motion of true polar wander tpw motion of the hotspot frame relative to the earth s spin axis assuming the duncan and clague 1985 model for pacific hotspots motion the sedimentary modeling favors tpw models which have little or no effect on the central pacific paleoequator over the past 30 ma we also explore implications of interhotspot motion and the suggestion that the bend in the hawaiian volcanic chain represents an abrupt change in pacific hotspot motion within the last 5 ma

summer temperature variations in the european alps a d 755 2004 abstract annually resolved summer temperatures for the european alps are described the reconstruction covers the a d 755 2004 period and is based on 180 recent and historic larch larix decidua mill density series the regional curve standardization method was applied to preserve interannual to multicentennial variations in this high elevation proxy dataset instrumental measurements from high low elevation grid boxes back to 1818 1760 reveal strongest growth response to current year june september mean temperatures the reconstruction correlates at 0 7 with high elevation temperatures back to 1818 with a greater signal in the higher frequency domain r 0 8 low elevation instrumental data back to 1760 agree with the reconstruction s interannual variation although a decoupling between warmer instrumental and cooler proxy data before 1840 is noted this offset is larger than during any period of overlap with more recent high elevation instrumental data even though the proxy time series

mediterranean drought fluctuation during the last 500 years based on tree ring data a 2 5 x 2 5 degrees gridded summer april september drought reconstruction over the larger mediterranean land area 32 5 degrees 47 5 degrees n 10 degrees w 50 degrees e 152 grid points is described based on a network of 165 tree ring series the drought index used is the self calibrated palmer drought severity index and the period considered is 1500 2000 the reconstruction technique combines an analogue technique for the estimation of missing tree ring data with an artificial neural network for optimal non linear calibration including a bootstrap error assessment tests were carried out on the various sources of error in the reconstructions errors related to the temporal variations of the number of proxies were tested by comparing four reconstructions calibrated with four different sized regressor datasets representing the decrease in the number of available proxies over time errors related to the heterogeneous spatial density of predictors were tested using pseudo proxies provided by the global climate model echo g finally the errors related to the imperfect climate signal recorded by tree ring series were tested by adding white noise to the pseudo proxies reconstructions pass standard cross validation tests nevertheless tests using pseudo proxies show that the reconstructions are less good in areas where proxies are rare but that the average reconstruction curve is robust finally the noise added to proxies which is by definition a high frequency component has a major effect on the low frequency signal but not on the medium frequencies the comparison of the low frequency trends of our mean reconstruction and the gcm simulation indicates that the detrending method used is able to preserve the long term variations of reconstructed pdsi the results also highlight similar multi decadal pdsi variations in the central and western parts of the mediterranean basin and less clear low frequency changes in the east the sixteenth and the first part of the seventeenth centuries are characterized by marked dry episodes in the west similar to those observed in the end of the twentieth century in contrast the eighteenth and nineteenth centuries little ice age are characterized by dominant wet periods in the eastern part of the mediterranean basin the observed strong drought period of the end of the twentieth century seems to be the strongest of the last 500 years

a 1052 year tree ring proxy for alpine summer temperatures a june august alpine temperature proxy series is developed back to ad 951 using 1 527 ring width measurements from living trees and relict wood the reconstruction is composed of larch data from four alpine valleys in switzerland and pine data from the western austrian alps these regions are situated in high elevation alpine environments where a spatially homogenous summer temperature signal exists in an attempt to capture the full frequency range of summer temperatures over the past millennium from inter annual to multi centennial scales the regional curve standardization technique is applied to the ring width measurements correlations of 0 65 and 0 86 after decadal smoothing with high elevation meteorological stations since 1864 indicate an optimal response of the rcs chronology to june august mean temperatures the proxy record reveals warm conditions from before ad 1000 into the thirteenth century followed by a prolonged cool period reaching minimum values in the 1820s and a warming trend into the twentieth century this latter trend and the higher frequency variations compare well with the actual high elevation temperature record the new central alpine proxy suggests that summer temperatures during the last decade are unprecedented over the past millennium it also reveals significant similarities at inter decadal to multi centennial frequencies with large scale temperature reconstructions however deviating during certain periods from h h lamb s european north atlantic temperature history

finite difference seismic modeling of axial magma chambers we tested the feasibility of using finite difference methods to model seismic propagation at 10 hz through a two dimensional representation of an axial magma chamber with a thin liquid lid our technique produces time series of displacement or pressure at seafloor receivers to mimic a seismic refraction experiment and snapshots of p and s energy propagation the results indicate that our implementation is stable for models with sharp velocity contrasts and complex geometries we observe a high energy downward traveling shear phase observable only with borehole receivers that would be useful in studying the nature and shape of magma chambers the ability of finite difference methods to model high order wave phenomena makes this method ideal for testing velocity models of spreading axes and for planning near axis drilling of the east pacific rise in order to optimize the benefits from shear wave imaging of sub axis structure

late holocene pinewoods persistence in the gredos mountains central spain inferred from extensive megafossil evidence macro and megafossil studies are of great value in palaeoecology because such evidence is spatially precise directly radiocarbon dated and usually taxon specific here we present new macro and megafossil data from ten sites from the gredos mountains central iberian peninsula that suggest persistent forest cover through the late holocene with a widespread belt of pinewoods in the highlands of the central iberian mountains well preserved pine cones found at several sites revealed that both pinus sylvestris and pinus nigra were present in the area during the middle and late holocene at locations of important biogeographical interest the p sylvestris forests represent one of the southernmost locations of its entire range p nigra was not known to have occurred in central spain during the holocene it was found at the westernmost edge of its range in siliceous soils a rare environment compared with the rest of its distribution finally we explored the potential for obtaining a long pine chronology from central iberia using tree ring measurements and radiocarbon dating of pine subfossil logs

structure of young oceanic crust at 13 n on the east pacific rise from expanding spread profiles we present the results of the analysis of expanding spread profiles esps collected on and near the axis of the east pacific rise at 13 n these profiles were collected at 0 1 1 2 1 3 6 and 9 5 km from the rise axis and all but the most distant profile show a distinct low velocity zone lvz located within layer 3 of the oceanic crust at the ridge crest the top of the magma chamber is at the base of layer 2 while 3 6 km off axis the roof of the lvz is 1 1 km below the top of layer 3 the profile farthest from the ridge could possibly have a residual lvz confined to the lower 1 5 km of the crust the total width of the lvz as determined from the esp data is at least 6 km and possibly much greater this wide lvz apparently contradicts multichannel seismic data which show cross axis reflections from the magma chamber with a width of 5 km we suggest that a resolution of this apparent contradiction lies in a model of the rise axis with a small and transient central magma chamber of high partial melt fraction surrounded by a much larger and permanent region of hot rock with only isolated pockets of partial melt the esp data are sensitive to this larger region while the reflection data accurately map the presence or absence of the central magma chamber with its high impedance contrast we identify the presence of a layer at the top of the oceanic crust with initial p wave velocities between 2 35 and 2 6 km s while the s wave velocity is estimated as being 0 8 km s the layer thickness lies between 100 and 200 m these velocities are consistent with previous estimates for the pacific and recent results for the atlantic the thickness of this layer is consistent with that of layer 2a determined from geophysical measurements at deep sea drilling project hole 504b

a matter of divergence tracking recent warming at hemispheric scales using tree ring data 1 no current tree ring tr based reconstruction of extratropical northern hemisphere enh temperatures that extends into the 1990s captures the full range of late 20th century warming observed in the instrumental record over recent decades a divergence between cooler reconstructed and warmer instrumental large scale temperatures is observed we hypothesize that this problem is partly related to the fact that some of the constituent chronologies used for previous reconstructions show divergence against local temperatures in the recent period in this study we compiled tr data and published local regional reconstructions that show no divergence against local temperatures these data have not been included in other large scale temperature reconstructions utilizing this data set we developed a new completely independent reconstruction of enh annual temperatures 1750 2000 this record is not meant to replace existing reconstructions but allows some degree of independent validation of these earlier studies as well as demonstrating that tr data can better model recent warming at large scales when careful selection of constituent chronologies is made at the local scale although the new series tracks the increase in enh annual temperatures over the last few decades better than any existing reconstruction it still slightly under predicts values in the post 1988 period we finally discuss possible reasons why it is so difficult to model post mid 1980s warming provide some possible alternative approaches with regards to the instrumental target and detail several recommendations that should be followed in future large scale reconstruction attempts that may result in more robust temperature estimates

stable isotope coherence in the earlywood and latewood of tree line conifers abstract annually resolved and replicated tree ring stable isotope series have the potential to reconstruct growing season environmental parameters over multi millennial timescales as this archive may require only minimal statistical detrending it has the potential to preserve a large portion of low frequency climate signals to date many studies have utilised only the latewood portion of the tree ring in an attempt to minimize carry over effects from previous year reserves and maximise the annual nature of the climate signal preserved however the old trees from tree line locations necessary to build long chronologies often display narrow ring widths