Temperature Reconstructions Research Articles

Testing the reliability of global surface temperature reconstructions of the Last Glacial Cycle with pseudo-proxy experiments

Abstract. Reconstructions of past variations in the global mean surface temperature (GMST) are used to characterise the Earth system response to perturbations and to validate Earth system simulations. Beyond the instrumental period, reconstructions rely on local proxy temperature records and algorithms aggregating these records. Here, we propose to establish standards for evaluating the performance of such reconstruction algorithms. Our framework relies on pseudo-proxy experiments (PPEs). That is, we test the ability of an algorithm to reconstruct a simulated GMST, using artificially generated proxy data created from the same simulation. We apply the framework to an adapted version of the GMST reconstruction algorithm used in Snyder (2016) and the metadata of the synthesis of marine proxy records for the temperature of the last 130 kyr from Jonkers et al. (2020). We use an ensemble of four transient simulations of the Last Glacial Cycle (LGC) or the last 25 kyr for the pseudo-proxy experiments. Given the dataset and the algorithm, we find that the reconstruction is reliable for timescales longer than 4 kyr during the last 25 kyr. However, beyond 40 kyr BP, age uncertainty limits the reconstruction reliability to timescales longer than 15 kyr. For the long timescales, uncertainty on temperature anomalies is caused by a factor that re-scales near-global-mean sea surface temperatures to GMST, the proxy measurements, the specific set of record locations, and potential seasonal biases. Increasing the number of records significantly reduces all sources of uncertainty but the scaling. We also show that a trade-off exists between the inclusion of many records, which reduces the uncertainty on long timescales, and of only records with low age uncertainty, high accumulation rate, and high resolution, which improves the reconstruction of the short timescales. Finally, the method and the quantitative results presented here can serve as a basis for future evaluations of reconstructions. We also suggest future avenues to improve reconstruction algorithms and discuss the key limitations arising from the proxy data properties.

Strong volcanic-induced climatic shocks on historical Moselle wine production

Abstract. In central and southern Europe, grapevine is a climate-sensitive agricultural product of great economic importance, both in historical times and today. We systematically investigated the climatic impact, focusing on volcanic-forced abrupt cooling, on two long annual records of wine production quantity (spanning 1444–1786) from the Moselle Valley in present-day Luxembourg, close to the northern limit of viticulture in Europe. We present a consistent picture of the impact of volcanic eruptions on wine production through climate. To this end, we applied superposed epoch analysis – an appropriate method for detecting episodic signals in non-stationary time series – in combination with a bootstrap procedure to estimate the statistical significance. We also assessed the long-term relationship between different annual and seasonal climate parameters and wine production in the Moselle Valley. Robust and highly significant wine production declines occurred in the years immediately following major volcanic events. Warmer and, to a lesser extent, drier climate conditions had a moderately strong, but persistent, positive effect on wine production. We also find a volcanic cooling signature in spring and summer in temperature reconstructions. However, the detected volcanic signature in the Moselle Valley wine production is considerably stronger than the one found for central Europe in tree-ring-based reconstructions and is instead more akin to the strong volcanic signature present in Fennoscandian tree-ring series. On the basis of our findings, we encourage further compilation, publication, and analyses of additional wine production series containing unique biological and climatic information.

Corrigendum to “Biomarker reconstructions of temperature and hydroclimate variability in Vietnam during Marine Isotope Stage 3” [Quat. Sci. Rev. 341 (2024) 108893]

Corrigendum to “Biomarker reconstructions of temperature and hydroclimate variability in Vietnam during Marine Isotope Stage 3” [Quat. Sci. Rev. 341 (2024) 108893]

Non-Negligible Factors Influence Tree-Ring-Based Temperature Reconstruction and Comparison over Mid-Latitude China

Warm-season mean maximum temperature changes over mid-latitude regions have been attracting increasing attention amid the background of global warming. In this study, we present three tree-ring width chronologies: Tongbai Mountain (TBM; 1916–2014), Shimen Mountain (SMM; 1663–2014), and Xinlong (XL; 1541–2014), derived respectively from the eastern Qinling Mountains, north–central China, and the eastern Tibetan Plateau. Therein, TBM and SMM are newly developed, while XL is a reanalysis. Correlation analysis with climatic factors reveals that these three chronologies exhibit the highest correlation with the May–July mean maximum temperature. Based on these chronologies, we conducted reconstructions of the May–July mean maximum temperature. Spatial correlation analysis of each reconstruction with concurrent observed data, as well as comparisons with nearby temperature reconstructions, indicates their large-scale representativeness. However, during the common period of 1916–2014, the three chronologies show weak correlations with each other at the interannual timescale. Furthermore, the 11-year running correlation coefficients among the three reconstructions fluctuated during this common period. Additionally, fluctuations were observed between the reconstructions from SMM and XL during the overlapping period of 1668–2009, suggesting that tree-ring-based temperature reconstructions may be inconsistent when compared over mid-latitude China. These inconsistent changes can be attributed to the regional differences in the May–July mean maximum temperature change, the influence of different precipitation signals on the maximum temperature, and the El Niño–Southern Oscillations.

Estimating ocean currents from the joint reconstruction of absolute dynamic topography and sea surface temperature through deep learning algorithms

Abstract. Our study focuses on absolute dynamic topography (ADT) and sea surface temperature (SST) mapping from satellite observations, with the primary objective of improving the satellite-derived ADT (and derived geostrophic currents) spatial resolution. Retrieving consistent high-resolution ADT and SST information from space is challenging, due to instrument limitations, sampling constraints, and degradations introduced by the interpolation algorithms used to obtain gap-free (L4) analyses. To address these issues, we developed and tested different deep learning methodologies, specifically convolutional neural network (CNN) models that were originally proposed for single-image super resolution. Building upon recent findings, we conduct an Observing System Simulation Experiment (OSSE) relying on Copernicus numerical model outputs (with respective temporal and spatial resolutions of 1 d and 1/24°), and we present a strategy for further refinements. Previous OSSEs combined low-resolution L4 satellite equivalent ADTs with high-resolution “perfectly known” SSTs to derive high-resolution sea surface dynamical features. Here, we introduce realistic SST L4 processing errors and modify the network to concurrently predict high-resolution SST and ADT from synthetic, satellite equivalent L4 products. This modification allows us to evaluate the potential enhancement in the ADT and SST mapping while integrating dynamical constraints through tailored, physics-informed loss functions. The neural networks are thus trained using OSSE data and subsequently applied to the Copernicus Marine Service satellite-derived ADTs and SSTs, allowing us to reconstruct super-resolved ADTs and geostrophic currents at the same spatiotemporal resolution of the model outputs employed for the OSSE. A 12-year-long time series of super-resolved geostrophic currents (2008–2019) is thus presented and validated against in situ-measured currents from drogued drifting buoys and via spectral analyses. This study suggests that CNNs are beneficial for improving standard altimetry mapping: they generally sharpen the ADT gradients, with consequent correction of the surface currents direction and intensities with respect to the altimeter-derived products. Our investigation is focused on the Mediterranean Sea, quite a challenging region due to its small Rossby deformation radius (around 10 km).

Southern Ocean control on atmospheric CO2 changes across late Pliocene Marine Isotope Stage M2

Abstract. During the Pliocene, atmospheric CO2 concentrations (pCO2) were probably sometimes similar to today's, and global average temperature was ∼3 °C higher than preindustrial. However, the relationships and phasing between variability in climate and pCO2 on orbital timescales are not well understood. Specifically, questions remain about the nature of a lag of pCO2 relative to benthic foraminiferal δ18O in late Pliocene Marine Isotope Stage (MIS) M2 (3300 ka), which was longer than during the Pleistocene. Here, we present a multiproxy paleoceanographic reconstruction of the late Pliocene subtropical–subantarctic zone. New dinoflagellate cyst assemblage data are combined with previously published sea surface temperature reconstructions to reveal past surface conditions, including latitudinal migrations of the subtropical front (STF) over the late Pliocene at Ocean Drilling Program (ODP) Site 1168, offshore of western Tasmania. We observe strong oceanographic variability at the STF over glacial–interglacial timescales, especially the interval (3320–3260 ka) across MIS M2. By providing tight and independent age constraints from benthic foraminiferal δ18O, we find that, much more than benthic δ18O or local SST, latitudinal migrations of the STF are tightly coupled to global pCO2 variations across the M2. Specifically, a northerly position of the STF during the MIS M2 deglaciation coincides with generally low pCO2. We postulate that the Southern Ocean CO2 outgassing varied strongly with migrations of the STF and that this in part accounted for the variability in pCO2 across MIS M2.

Reconstruction of Cloudy Land Surface Temperature by Combining Surface Energy Balance Theory and Solar-Cloud-Satellite Geometry

Reconstruction of Cloudy Land Surface Temperature by Combining Surface Energy Balance Theory and Solar-Cloud-Satellite Geometry

Forensically useful mid-term and short-term temperature reconstruction for quasi-indoor death scenes.

While estimating postmortem interval (PMI) ambient temperature plays a pivotal role, so its reconstruction is crucial for forensic scientists. The recommended procedure is to correct temperatures from the nearest meteorological station based on measurements from the death scene; typically applying linear regression. Recently, there have been attempts to use different algorithms, that can improve that correction, for example GAM algorithm. Unfortunately, the improvements are usually a consequence of using more dependent variables than just the temperature from the death scene (e.g. humidity), which is impractical. This study develops practical new methods to accurately reconstruct ambient temperatures at a death scene, using just temperature measurements. Since the main difficulty preventing practitioners from using the correction protocol more frequently is likely the need to record temperatures on-site for at least several days, we searched for possibilities to shorten the measurement period. For this purpose, we tested two less popular algorithms to achieve this goal. The concurrent regression model (the model from the functional data analysis field) for the mid-term reconstruction (measurements lasting several days) and the functional model based on Fourier expansion for the short-term reconstruction (measurements lasting a few hours). The algorithms' performance was tested using data collected in six places: a roof and an attic of a heated building, an unheated garage inside the heated building, an unheated wooden shack, an uninhabited building, and an underground (the data logger was buried about 30 cm below the ground level). We classified these locations as quasi-indoor conditions, contrasting them with typical indoor conditions, where temperatures are nearly constant, and typical outdoor conditions, where there is no heat insulation. The mid-term model reduced error compared to the linear regression, providing nearly perfect reconstruction for measurement periods longer than six days. More importantly, however, the accuracy of short-term reconstruction was also high. The short-term model closely matched the concurrent regression model's performance after only four to five hours of measurements. In practice, both methods are very similar to the standard procedure. The main difference is the change in the algorithm and its implementation. In conclusion, this study demonstrates that correction of weather station temperatures can provide fairly accurate temperature data for use in estimating PMI after only 4-5 h of measurements on a death scene.

The need for high-resolution paleoclimate research

Comparing recent warming against past temperature changes is crucial for understanding the importance of greenhouse gas emissions for the global climate system. Although tree ring-based temperature and hydroclimate reconstructions form the backbone of high-resolution paleoclimatology, the data used, methods applied, and concepts proposed are far from perfect. Here, we open dialogue on challenges of dendroclimatology and scientific collaboration. We emphasise that temperature signals in tree-ring chronologies are restricted to extra-tropical growing seasons, and that far too little such data exist for the Southern Hemisphere and the Common Era. We notice that the preservation of both, high- and low-frequency information is prone to uncertainties, that investigations of growth-climate relations are hindered by short and spatially inconsistent meteorological measurements, and that geopolitical tension increasingly constrains data accessibility. Finally, we highlight the need for paleoclimate research and funding, with a focus on annually resolved and absolutely dated timeseries for the Holocene.

The role of neotectonics and climate variability in the Pleistocene-to-Holocene hydrological evolution of the Fuente de Piedra playa lake (southern Iberian Peninsula)

Abstract. Playa lakes that developed in semi-arid regions are sensitive to water input reductions, which may be influenced not only by climate changes and human management, but also by changes in the size of the watershed. We conducted an interdisciplinary study combining structural, geomorphic, sedimentological, mineralogical and hydrological analyses to better understand the evolution of the Fuente de Piedra (FdP) playa lake in southern Spain. By using previously published temperature and precipitation reconstructions, we assessed the potential evapotranspiration and runoff to estimate the maximum lake level during the FdP playa-lake lifespan (>35 ka). Our results indicate that the FdP playa-lake level never exceeded 5 m, although deposits at its north-eastern margin are up to 15 m above the current lake bed at present. These lacustrine deposits are slightly tilted towards the south-west. The electrical conductivity profiles of groundwater on the FdP's shore and in its surroundings reveal a more pronounced interface between brackish water and brine in the northern part of the basin compared to the southern part. This implies that saline water once occupied the northern playa-lake margin in an area that is hardly ever flooded at present. The presence of reworked gypsum in the sedimentary sequence of the southern margin (down to a depth of 14 m) indicates substantial erosion of prior gypsum deposits that are possibly redistributed from northern deposition areas. Altogether, our data suggest a south-westerly displacement of the playa-lake depocentre caused by an uplift of the eastern area and subsidence of the south-western area. This shift is congruent with the combined effect of both the La Nava sinistral–normal fault and the Las Latas dextral–normal fault at the eastern and southern margins of the FdP playa lake. Consequently, the FdP flooded surface mostly remained constant and in equilibrium with climate variables and its watershed along its lifespan. The south-westerly displacement of the flooded surface was provoked by the recent tectonic activity.

A hybrid statistical–dynamical framework for compound coastal flooding analysis

Abstract Compound coastal flooding due to astronomic, atmospheric, oceanographic, and hydrologic forcings poses severe threats to coastal communities. While physics-driven approaches are able to dynamically simulate temporally and spatially varying compound flooding generated by multiple partially correlated drivers, computational burdens limit their capability to explore the full range of conditions that contribute to compound coastal hazards. Data-driven statistical approaches address some of these computational challenges, however they are also unable to explore all possible forcing combinations due to short observational records, and projections are typically limited to a few locations. This study proposes a hybrid statistical-dynamical framework for compound coastal flooding analysis that integrates a stochastic generator of compound flooding drivers, a hydrodynamic model, and a machine learning-based surrogate model. The framework is demonstrated in San Francisco (SF) Bay over the past 500 years with high accuracy and computational efficiency. The stochastic generator of compound flooding drivers is developed by coupling a sea surface temperature (SST) reconstruction model with a climate emulator, weather generator, and hydrologic model. Using reconstructed SSTs as input, the generator of compound flooding drivers is employed to simulate time series of the forcing factors contributing to compound flooding in SF Bay. A process-based hydrodynamic model is built to predict total water levels (TWLs) varying in time and space throughout SF Bay based on the stochastically generated drivers. A machine learning-based surrogate model is then developed from a relatively small library of hydrodynamic model simulations to efficiently predict water levels (WLs) for compound flooding analysis under the full range of stochastic drivers. This study contributes a hybrid statistical-dynamical framework to better understand the spatial distribution and temporal evolution of compound coastal flooding, along with the relative contributions of the forcing drivers in complex nearshore, estuarine, and river environments for centennial timescales under past, present, and future climates.

Comparative study on brightness temperature reconstruction of synthetic aperture based on deep learning

In order to study the effect of deep learning method in the brightness temperature reconstruction of synthetic aperture radiometer, the gray value of remote sensing image with channel amplitude-phase error and random error is used as the original brightness temperature image for simulation experiment to compare the brightness temperature reconstruction images under traditional Fourier transform, CNN inversion, U-net inversion and Resnet inversion. From the view of image visual effect, Resnet inversion method has the best image restoration effect and the weakest background noise. From the evaluation index, the RMSE of Resnet inversion method is the smallest, which is 6.28K, and the PNSR value is the highest, which is 31.62dB. The second is CNN inversion method, RMSE value is 10.93K, PNSR value is 27.09dB. Therefore, Resnet inversion method can better restore bright temperature image, reduce Gibbs effect and improve image resolution.

Discrepancies in lacustrine bacterial lipid temperature reconstructions explained by microbial ecology

Bacterial lipid branched glycerol dialkyl glycerol tetraethers (brGDGTs) are a valuable tool for reconstructing past temperatures. However, a gap remains regarding the influence of bacterial communities on brGDGT profiles. Here, we identified two distinct patterns of brGDGTs from the surface sediments of 38 Tibetan Plateau lakes using an unsupervised clustering technique. Further investigation revealed that salinity and pH significantly change bacterial community composition, affecting brGDGT profiles and causing brGDGT-based temperatures to be overestimated by up to 2.7 ± 0.7 °C in haloalkaline environments. We subsequently used the trained clustering model to examine the patterns of bacterial assemblages in the global lacustrine brGDGT dataset, confirming the global applicability of our approach. We finally applied our approach to Holocene brGDGT records from the Tibetan Plateau, showing that shifts in bacterial clusters amplified temperature variations over timescales. Our findings demonstrate that microbial ecology can robustly diagnose and constrain site-specific discrepancies in temperature reconstruction.

Silicoflagellate assemblages in the North Pacific surface sediments: an application of the modern analog method to reconstruct the glacial sea surface temperature in the Japan Sea

Recent silicoflagellate distributions have been examined in 195 surface sediment samples from the North Pacific to establish the silicoflagellate assemblage dataset from surface sediments across the North Pacific for paleo sea surface temperature (SST) reconstruction. The relative abundance data of all seven silicoflagellate taxa identified in this study were used for the modern analog method to reconstruct past SST. The SST reconstruction based on the silicoflagellate modern analog technique was applied to the two sediment cores from the Japan Sea. With the development of ice sheets, the Japan Sea experienced a low salinity isolation event during the Last Glacial Maximum (LGM: 19 ka–26.5 ka), which hampers the SST reconstruction employing geochemical proxies such as alkenone and Mg/Ca thermometry. The reconstructed glacial SST between 25 and 15 ka was ~ 5 °C in the northern and southern Japan Sea, indicating significant southward migration of the glacial subpolar front. The timings of the deglacial SST rises were ~ 14 ka at the south core site and ~ 10 ka at the north core site, indicating a latitudinal lag. This lag likely reflects a gradual increase in the fluxes of the Tsushima Warm Current from the East China Sea through the Tsushima Strait. Compilation of the silicoflagellate assemblages in the North Pacific surface sediments used for the modern analog technique to reconstruct past sea surface temperature (SST), revealing the Japan Sea SST during the last glacial maximum ~20 ka ago.

Western Pacific Warm Pool Warming and Salinity Front Expansion Since 1821 Reconstructed From Paired Coral δ18O, Sr/Ca, and Reconstructed δ18Osw

AbstractThe Southwest Pacific region is of great importance to global climate variability, but instrumental climate observations before the 1980s lack in numbers and quality. Despite efforts in complementing instrumental records with proxy sea surface temperature (SST) and sea surface salinity (SSS) reconstructions based on coral Sr/Ca and δ18Osw records, few of them are longer than a century. This study introduces a northwestern extension to the existing records of South Pacific coral study sites with monthly‐resolved Sr/Ca, δ18O, and δ18Osw reconstructions from Rotuma dating back to 1821. Additionally, we present new monthly‐resolved Sr/Ca and reconstructed δ18Osw from a coral from Tonga dating back to 1848. Results reveal 1.5°C warming in the Western Pacific Warm Pool, while the adjacent coral from Tonga shows 1°C warming over the twentieth century. The Rotuma Sr/Ca record reveals thermal stress events impacting the Sr/Ca‐SST relationship in the following months. Coral δ18Osw results reveal significant freshening of 0.45 Sp (practical salinity unit) in Tonga since the early twentieth century, suggesting the southeastward expansion of the South Pacific Convergence Zone salinity front. The δ18Osw inferred SSS provides a valuable extension into the past considering the short and inconsistent instrumental records available. This study demonstrates the utility of coral‐based reconstructions in capturing long‐term and regional climate variations in the Southwest Pacific and the necessity of expanding replicated studies to other underrepresented areas to enhance our understanding of regional climate dynamics.

Spatial and Temporal Bayesian Hierarchical Model Over Large Domains With Application to Holocene Sea Surface Temperature Reconstruction in the Equatorial Pacific

AbstractWe present a novel space‐time Bayesian hierarchical model (BHM) to reconstruct annual Sea Surface Temperature (SST) over a large domain based on SST at limited proxy (i.e., sediment core) locations. The model is tested in the equatorial Pacific. The BHM leverages Principal Component Analysis to identify dominant space‐time modes of contemporary variability of the SST field at the proxy locations and employs these modes in a Gaussian process framework to estimate SSTs across the entire domain. The BHM allows us to model the mean field and covariance, varying in space and time in the process layers of the hierarchy. Using the Markov Chain Monte Carlo (MCMC) method and suitable priors on the model parameters, posterior distributions of the model parameters and, consequently, posterior distributions of the SST fields and the attendant uncertainties are obtained for any desired year. The BHM is calibrated and validated in the contemporary period (1854–2014) and subsequently applied to reconstruct SST fields during the Holocene (0–10 ka). Results are consistent with prior inferences of La Niña‐like conditions during the Holocene. This modeling framework opens exciting prospects for modeling and reconstruction of other fields, such as precipitation, drought indices, and vegetation.

Holocene seasonal temperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) records from different regions in China

The patterns of Holocene temperature change can provide important insight for understanding the recent global warming and assessing future global climate change. However, the mismatch in Holocene mean annual temperature between proxy records and climate models remains controversial, which is likely caused by potential seasonal bias from the geological records. Here, 64 surface sediment samples are analyzed to examine the seasonal bias of brGDGTs reconstruction. Subsequently, we compile 23 brGDGT-based seasonal and annual temperature records from different regions in China and compare them with the TraCE-21 ka simulation results in the same geographical location. The linearly analysis shows a higher correlation between MBT′5me and MAF (mean temperature of months above freezing) than that of MAT (mean annual air temperatures), suggesting the reconstructed temperature based on brGDGTs from aquatic sources may be biased toward MAF. The regionally stacked results indicate that MAF in the Qinghai-Tibet Plateau and Northern China warmed from ~12 to 7 ka BP and then cooled thereafter, while an overall warming trend occurred in Southern China. These patterns of MAF change can be well reproduced by the model simulations. The summer and autumn temperature patterns during the Holocene in the Northern China are primarily driven by local insolation and modulated by ice sheets and greenhouse gas concentrations. The retreat of ice sheets in the early and middle Holocene, coupled with the increase in greenhouse gases, is considered the main driving factor for the long-term warming trend of the Holocene in southern China, whereas orbital-induced summer temperature change might be the major driving factor of MAF change in the Qinghai-Tibet Plateau. Our results suggest that the patterns of seasonal temperature change are basically matched between proxy records and climate models during the Holocene.

Replicability of paleotemperature records in the northern Okinawa Trough and its implications for paleoceanographic reconstructions

Geochemical proxies are frequently utilized in the reconstruction of past ocean temperatures. Due to resource constraints, these reconstructions typically rely on a single sediment core, raising questions about the local and regional representativeness of paleotemperature records. To address this, we analyzed four sediment cores located within a 10-km radius in the northern Okinawa Trough (OT), which share the same climatic forcing and thus should reflect similar climate variations. We compiled published data and generated new paleotemperature estimates based on three widely used geochemical proxies (foraminiferal Mg/Ca, U37K′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{U}}_{37}^{{{\ ext{K}}^{\\prime}}}$$\\end{document}, TEX86\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{TEX}}_{86}$$\\end{document}). Analysis of the mean absolute deviations for nearby records based on the same proxy revealed that U37K′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{U}}_{37}^{{{\ ext{K}}^{\\prime}}}$$\\end{document} has the highest reproducibility, followed by Mg/Ca and TEX86\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{TEX}}_{86}$$\\end{document}. However, inconsistencies in inter-proxy offsets among nearby sites suggest the presence of noise in the proxy records, likely stemming from instrumental errors and sediment heterogeneity. Furthermore, the Mg/Ca and U37K′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{U}}_{37}^{{{\ ext{K}}^{\\prime}}}$$\\end{document} paleotemperature records agree within uncertainty when accounting for inter-site variability and calibration uncertainties, challenging previous interpretations of temperature signals from different seasons. All proxies indicate similar glacial-interglacial trends, albeit with varying magnitudes of temperature change. Both Mg/Ca and U37K′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{U}}_{37}^{{{\ ext{K}}^{\\prime}}}$$\\end{document} records suggest a glacial cooling of ~ 3 °C, whereas TEX86\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{TEX}}_{86}$$\\end{document} sea surface temperature (SST) data indicate a stronger glacial cooling of approximately ~ 6–8 °C. Modern observations indicate a subsurface TEX86\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{TEX}}_{86}$$\\end{document} recording depth of 50–100 m, coinciding with the thermocline. However, the TEX86\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{TEX}}_{86}$$\\end{document} subsurface temperature (subT) record does not resemble the Mg/Ca records of thermocline-dwelling foraminifera species. Instead, there is a better agreement with benthic foraminiferal Mg/Ca records of Uvigerina spp. (~ 700 m) and the intermediate temperature record derived from radiolarian assemblages (~ 500 m), pointing to a TEX86\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{TEX}}_{86}$$\\end{document} recording depth that is deeper than the thermocline. In summary, our findings show that proxy noise can impact inter-proxy comparisons of paleotemperature records, but not the direction of glacial-interglacial shifts. Future research should prioritize constraining the recording depth of paleotemperature proxies and reducing calibration uncertainty for more precise and reliable quantitative paleotemperature reconstruction.

Reconstruction of Surface Water Temperature in Lakes as a Source for Long-Term Analysis of Its Changes

Reconstruction of Surface Water Temperature in Lakes as a Source for Long-Term Analysis of Its Changes

Temperature reconstruction in data centers using gappy pod combined with genetic algorithm and optimization of sensor layout

Temperature reconstruction in data centers using gappy pod combined with genetic algorithm and optimization of sensor layout