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While it is clear that vegetation takes part in shaping terrestrial climate through various interactions with the atmosphere, it is not so obvious what role plant functional diversity plays here. So far a tool for investigating this question in land-atmosphere simulations was missing. The new tool JeDi-BACH (version 1.0), described here, closes this gap by combining the Jena Diversity Model (JeDi) with the land component JSBACHv4 of the ICON Earth System Model (version 1.0). In practice, the low-diversity plant parametrization of JSBACH employing plant functional types (PFTs) was replaced by the trait-based high-diversity vegetation description of JeDi. The novelty of JeDi is that the composition of terrestrial ecosystems emerges dynamically from environmental filtering based on functional trade-offs. Thereby, in contrast to the PFT approach, a richer set of plant strategies adapted to the ruling environmental conditions is obtained without a priori knowledge of the vegetation distribution. Besides documentation of this new implementation of JeDi, the paper also presents results from first exploratory simulations with interactive land-atmosphere coupling. We find a systematic dependence of terrestrial climate on diversity. Moreover, when investigating the reaction to changes in trait parameters, we find that at low diversity, climate depends strongly on the particular composition of vegetation, while at high diversity terrestrial climate proves to be rather resilient due to a dynamic re-organization of the plant community structure. Apparently, the many more dynamic degrees of freedom of the highly diverse vegetation in JeDi-BACH make this model behave very differently (less tunable) than conventional land components based on only a few PFTs. Besides fundamental research on the relation between diversity and climate, JeDi-BACH may be useful for the investigation of non-analogue climates (e.g., paleoclimate) where we lack knowledge on the structure and distribution of vegetation. [ABSTRACT FROM AUTHOR]

Proxy system models (PSMs) are an essential component of paleoclimate data assimilation and for testing climate field reconstruction methods. Generally, current statistical PSMs consider the noise in the output (proxy) variable only and ignore the noise in the input (environmental) variables. This problem is exacerbated when there are several input variables. Here we develop a new PSM, the Measurement Error Proxy System Model (MEPSM), which includes noise in all variables, including noise auto- and cross-correlation. The MEPSM is calibrated using a quasi-Bayesian solution, which leverages Gaussian conjugacy to produce a fast solution. Another advantage of MEPSM is that the prior can be used to stabilize the solution between an informative prior (e.g., with a non-zero mean) and the maximum likelihood solution. MEPSM is illustrated by calibrating a proxy model for δ18Ocoral with multiple inputs (marine temperature and salinity), including noise in all variables. MEPSM is applicable to many different climate proxies and will improve our understanding of the effects of predictor noise on PSMs, data assimilation, and climate reconstruction. [ABSTRACT FROM AUTHOR]

Cr(VI) is a carcinogen with proven mutagenic and genotoxic effects. The effects of the depositional environment (e.g., paleoweathering, paleoclimate, and paleoredox condition) on Cr enrichment in non-ultramafic aquifer solids are unclear. In this study, we presented the sedimentary characteristics of a borehole from a typical non-ultramafic aquifer with high Cr groundwater in Jingbian, central Ordos Basin, China. Chromium was enriched in the K1h sandstone aquifer, especially at depths of 400–500 m, with the highest value of mass transport coefficient (τAl,Cr) up to 92.13% and τAl,Fe up to 33.5%. The provenance of aquifer Cr was predominantly intermediate and felsic igneous rocks with a mafic rock mixture. This mafic source was inferred from Cr-rich granodiorite and mafic/ultramafic rocks in the Yinshan (Daqingshan–Wulashan) Block, northern Ordos Basin. The Cr-rich aquifer in K1h was developed due to a moderate chemical index of alteration (CIA) (mean, 56.7) under relatively warm and humid paleoclimate, as evidenced by high CIA-temperature (CIA-Temp) (mean, 6.79 °C) and paleoclimatic index values (mean, 0.40). Fe–Mn redox cycling in the oxic to suboxic environments contributed to aquifer Cr accumulation. Using path analysis, we identified that paleoclimate created favorable weathering conditions and enrichment of Fe contributed to the formation of high-Cr aquifers. The study reveals the formation of positive Cr anomalies in non-ultramafic aquifers, which is the potential source of groundwater Cr, and highlights the effects of depositional factors on Cr accumulation during aquifer deposition or early diagenesis. It can provide new insights into the natural processes of high-Cr sediments occurring in non-ultramafic aquifers. [ABSTRACT FROM AUTHOR]

[Display omitted] The term "Holocene temperature conundrum" refers to the inconsistencies between proxy-based reconstructions and transient model simulations, and it challenges our understanding of global temperature evolution during the Holocene. Climate reconstructions indicate a cooling trend following the Holocene Thermal Maximum, while model simulations indicate a consistent warming trend due to ice-sheet retreat and rising greenhouse gas concentrations. Various factors, such as seasonal biases and overlooked feedback processes, have been proposed as potential causes for this discrepancy. In this study, we examined the impact of vegetation-climate feedback on the temperature anomaly patterns in East Asia during the mid-Holocene (∼6 ka). By utilizing the fully coupled Earth system model EC-Earth and performing simulations with and without coupled dynamic vegetation, our objective was to isolate the influence of vegetation changes on regional temperature patterns. Our findings reveal that vegetation-climate feedback contributed to warming across most of East Asia, resulting in spatially diverse temperature changes during the mid-Holocene and significantly improved model-data agreement. These results highlight the crucial role of vegetation-climate feedback in addressing the Holocene temperature conundrum and emphasize its importance for simulating accurate climate scenarios. [ABSTRACT FROM AUTHOR]

The Atlantic Meridional Overturning Circulation (AMOC) forms an essential component of the global ocean circulation. Paleoclimate records indicate the AMOC’s capability to tip between different states that resulted in large global climate impacts. Using an AMOC box model, re‐calibrated against a global circulation model, HadGEM3, we present a new bifurcation analysis and showcase mechanisms that may lead the AMOC to tip from its current ‘on’ state to a collapsed ‘off’ state under climate change. We find that bifurcation‐ and noise‐induced tipping remain viable tipping mechanisms as in previous calibrations, while rate‐induced tipping only occurs for specific parameter configurations of this model. [ABSTRACT FROM AUTHOR]

Paleoclimate records have been used to estimate the modern equilibrium climate sensitivity. However, this requires understanding how the feedbacks governing the climate response vary with the climate itself. Here we warm and cool a state-of-the-art climate model to simulate a continuum of climates ranging from a nearly ice-covered Snowball Earth to a nearly ice-free hothouse. We find that the pre-industrial (PI) climate is near a stability optimum: warming leads to a less-stable (more-sensitive) climate, as does cooling of more than 2K. Physically interpreting the results, we find that the decrease in stability for climates colder than the PI occurs mainly due to the albedo and lapse-rate feedbacks, and the decrease in stability for warmer climates occurs mainly due to the cloud feedback. These results imply that paleoclimate records provide a stronger constraint than has been calculated in previous studies, suggesting a reduction in the uncertainty range of the climate sensitivity. Climate model simulations show that Earth's current climate is near a stability optimum, with warming and substantial cooling both leading to less stable and hence more sensitive climates. [ABSTRACT FROM AUTHOR]

Multiple geochemical proxies (e.g., trace elements, δ18O and δ13C) and precise 230Th ages in speleothems are crucial for conducting robust paleoclimatic reconstructions, but the impact of diagenesis on these proxies and 230Th ages is not well-established. In this study, we investigate the petrography and geochemical composition of six aragonite-calcite stalagmites from Shennong Cave in southeastern China to analyze the transformation from aragonite to calcite (primary versus secondary) and its effects on geochemical proxies and 230Th ages. No aragonite relics are observed in columnar calcite in four aragonite-calcite stalagmites (SN55, SN49, SN104 and SNB1), although traces of aragonite exist between the calcite crystals or grow parallel at the aragonite-calcite borders. This is different from the obvious aragonite relics preserved in secondary mosaic calcite in the other two aragonite-calcite stalagmites (SN3 and SN15). Both mosaic and columnar calcite show various changes in geochemical proxies and 230Th ages compared with primary aragonite. The trend in the geochemical proxies analyzed (trace elements, δ18O and δ13C) of columnar calcite remains consistent with those of aragonite, despite significant differences in their absolute values within the overlapping periods. These differences are due to the different fractionation coefficients of isotopes and trace elements in aragonite and calcite formed under the same solution conditions rather than late diagenesis. The 230Th ages of columnar calcite are similar to those of primary aragonite, and the values of subsamples from the same calcite layer are consistent. In contrast, the trace elements and δ13C values of mosaic calcite are similar to those of primary aragonite, while its 230Th age significantly differs from that of primary aragonite, exhibiting no consistent patterns. Therefore, these geochemical characteristics of columnar calcite are significantly different from secondary mosaic calcite, indicating that the columnar calcite in these four aragonite-calcite stalagmites is primary. A comparison of trace elements and δ13C records between aragonite-calcite and pure aragonite stalagmites during the overlapping period further confirms that these columnar calcites are primary. Their geochemical proxies can be used for paleoclimate reconstruction after careful evaluation, and the transformation from aragonite to columnar calcite is caused by increased precipitation. However, due to age and geochemical proxies change, secondary mosaic calcite is unsuitable for paleoclimate reconstruction, unlike columnar calcite. This study provides competent evidence to identify whether calcite in aragonite-calcite stalagmites is primary versus secondary and whether it can be used for paleoclimatic reconstruction. [ABSTRACT FROM AUTHOR]

The "4.2 ka event" is a commonly described abrupt climate excursion that occurred about 4200 years ago. However, the extent to which this event is coherent across regional and larger scales is unclear. To objectively assess climate excursions in the Holocene we compile 1142 paleoclimate datasets that span all continents and oceans and include a wide variety of archive and proxy types. We analyze these data to determine the timing, significance and spatial imprint of climate excursions using an objective method that quantifies local, regional and global significance. Site-level excursions in temperature and hydroclimate are common throughout the Holocene, but significant global-scale excursions are rare. The most prominent excursion occurred 8200 years ago, when cold and dry conditions formed a large, significant excursion centered in the North Atlantic. We find additional significant excursions between 1600 and 1000 years ago, which agree with tree-ring data and annual-scale paleoclimate reconstructions, adding confidence and context to our findings. In contrast, although some datasets show significant climate excursions 4200 years ago, they do not occur in large, coherent spatial regions. Consequently, like most other periods in the Holocene, the "4.2 ka event" is not a globally significant climate excursion. A study of more than 1000 paleoclimate datasets reveals that the "4.2 ka event" is not a globally significant climate excursion, unlike the prominent 8.2 ka event. In the Holocene, site-level excursions are common, but global-scale events are rare. [ABSTRACT FROM AUTHOR]

Stable isotope abundances (δ18O and δ2H) in regional aquifers can provide important paleoclimate information. However, identifying paleoclimate signals can be complicated by cross-formational mixing and, potentially, by isotopic diffusion between aquifers and confining units. We examine controls on δ18O and δ2H distributions in the Wilcox aquifer of the northern Gulf Coastal Plain (USA). We sampled groundwater for δ18O, δ2H, Cl−, and 36Cl along a ~300 km downgradient transect. We developed a simplified, 1D numerical model of groundwater flow and 18O transport to assess the possible importance of isotopic diffusion between the aquifer and its confining units. Along the inferred flowpath, δ18O and δ2H values were depleted by as much as 1.3 and 8.2‰, respectively, as the Wilcox aquifer transitioned from unconfined to confined. However, they then gradually rose farther downgradient by up to 1.1 and 8.6‰. Chlorine-36 analyses and 14C analyses (from other studies) indicate that groundwater ages range from ~103 yr to ~8 × 105 yr. Modeling results indicate that the effect of diffusion on isotopic abundances is limited, whereas Cl− data indicate that cross-formational flow is limited. Therefore, we posit that confined groundwater in our study reflects a Pleistocene paleorecharge signal. [ABSTRACT FROM AUTHOR]

Coral‐based stable oxygen isotopes (δ18O) have been used as a proxy for sea surface temperature (SST) since the 1970s, and δ18O–SST calibration studies have been fundamental to assure robust and faithful SST reconstructions. Paleoclimatic studies based on corals from the tropical western South Atlantic (TWSA) are scarce, and the available coral species need to be calibrated to improve climate and environmental reconstructions. Siderastrea stellata, a slow‐growing coral, is a potential species to be explored as a coral archive in the TWSA. We provide the first multi‐site δ18O–SST calibration for the coral S. stellata from three locations at the TWSA: Todos os Santos Bay, Tamandaré and the Rocas Atoll. Pseudo‐coral δ18O calculations derived from gridded SSS and SST show that the contributions of SSS and SST to coral δ18O are expected to be different at each site. Weighted least squares linear regressions performed between the δ18O and SST generated the following calibrations equations: δ18O = −0.18 (±0.02) × SST (°C) + 1.90 (±0.47) for Todos os Santos Bay; δ18O = −0.18 (±0.02) × SST (°C) + 1.54 (±0.67) for Tamandaré; and δ18O = −0.16 (±0.03) × SST (°C) + 1.24 (±0.71) for the Rocas Atoll. The δ18O‐SST sensitivity of S. stellata from the TWSA is similar to that of other slow‐growing species of the genus and consistent with the expected δ18O‐SST sensitivity of other species reported in the literature. These calibrations will allow future SST reconstructions based on δ18O records from sub‐fossil and fossil S. stellata, an abundant species in the TWSA. Plain Language Summary: Corals continuously biomineralize calcium carbonate, storing environmental information within their exoskeletons in geochemical and isotopic records that span hundreds of years and making them suitable for high‐resolution climate reconstructions. The stable oxygen isotopes (δ18O) found in corals are an important proxy for revealing past sea surface temperatures (SST) and sea surface salinities (SSS). However, to ensure that this proxy is applicable to reconstruct past SST, further δ18O–SST calibration studies are needed on various regions and species. In this study, we carried out three field work experiments to provide the first multi‐site δ18O–SST calibration of the slow‐growing coral Siderastrea stellata from the western South Atlantic. Despite the slow growth nature of S. stellata corals that poses a challenge to high temporal resolution sampling, we successfully provided new calibration equations for SST reconstruction from three different locations in the western South Atlantic. Our calibration equations can now be applied to reconstruct SST based on coral δ18O records from sub‐fossil and fossil coral cores. Key Points: First multi‐site δ18O‐SST calibrations for the slow‐growing coral Siderastrea stellata from the western South Atlanticδ18O–SST sensitivity for S. stellata varied from −0.15 to −0.19‰ per °C across the different reef environmentsThis study paves the way for using S. stellata δ18O from fossil and subfossil corals for paleoclimate reconstructions from the western South Atlantic [ABSTRACT FROM AUTHOR]

In 2017 El Niño Costero devastated the northern coast of Peru. This article seeks to learn from this experience for future large central and eastern Pacific-driven El Niño events. It directs attention away from dominant disaster narratives to reflect on the opportunities that El Niño rains have generated for desert livelihoods over time. We make a call for and set out the key elements of a historical geographical ethnography approach in environmental geography, which, as well as examining climate dimensions (paleoclimatology, dendrochronological, and atmospheric changes) of El Niño, also aims to consider its impacts on the livelihoods and management strategies of desert communities over time. We take as a starting point the responses of people who themselves come directly into contact with environmental change, yet whose agency and experiences are often marginal in knowledge production about El Niño. Responding to recent calls for qualitative geography researchers to be more explicit about how data are collected and analyzed, we explain how and why it is important to compare stakeholder interviews and climate records with newspaper archives and community memories of the 1983 and 1998 El Niño events. We illustrate that for desert populations in northern Peru, El Niño can represent abundance as well as disaster and make visible their role in managing change after El Niño flooding. [ABSTRACT FROM AUTHOR]

Identifying tropical cyclone (TC) signatures in paleoclimate records enhances our understanding of long-term TC activity trends and the climatic factors influencing TC evolution. Stalagmites are considered promising archives for recording TC activity. However, despite the western North Pacific being the most TC-active ocean basin globally, it lacks stalagmite-based TC reconstructions. Here, we present a seasonally resolved stalagmite δ18O record from XRY cave in Southeast China, covering the period from 1951 to 2018 CE, to identify annual signals of strong TC activity. We propose that the minimum seasonal XRY δ18O value of each year can reconstruct regional TC activity, achieving an identification rate of 86% for strong TC years in study area. This demonstrates the feasibility of using stalagmites for TC reconstruction in Southeast China. Moreover, our research shows that inland stalagmites can still capture TC activity signals, which will promote the use of stalagmites in obtaining long-term records of post-landfall TC activity and inland impacts. [ABSTRACT FROM AUTHOR]

Tree rings are the most widely‐used proxy records for reconstructing Common Era temperatures. Tree‐ring records correlate strongly with temperature on an interannual basis, but studies have found discrepancies between tree rings and climate models on longer timescales, indicating that low‐frequency noise could be prevalent in these archives. Using a large network of temperature‐sensitive tree‐ring records, we partition timeseries variance into a common (i.e., "signal") and non‐climatic (i.e., "noise") component using a frequency‐resolved signal‐to‐noise ratio (SNR) analysis. We find that the availability of stored resources from prior years (i.e., biological "memory") dampens the climate signal at high‐frequencies, and that independent noise reduces the SNR on long timescales. We also find that well‐replicated, millennial‐length records had the strongest common signal across centuries. Our work suggests that low‐frequency noise models are appropriate for use in pseudoproxy experiments, and speaks to the continued value of high‐quality data development as a top priority in dendroclimatology. Plain Language Summary: Tree rings contain valuable information about past variations in Earth's climate, but this information can be obscured by biological influences over tree‐ring formation, particularly when slow changes in climate are integrated with long biological trends. In this study, we measured the strength of the common signal and random noise in a network of tree‐ring records from across the Northern Hemisphere. We find that the emergence of non‐climatic trends decreases the similarity of nearby tree‐ring records to each other on long timescales. Key Points: Temperature‐sensitive tree‐ring records had the highest signal‐to‐noise ratios on an interannual basisNoise showed a positive relationship with timescale indicating presence of independent trends over long time periodsSignal‐to‐noise ratios were highest in tree‐ring density records and in records comprised of a greater number of individual trees [ABSTRACT FROM AUTHOR]

Over recent decades, the southeastern United States (Southeast) has become increasingly well represented by the terrestrial climate proxy record. However, while the paleo proxy records capture the region's hydroclimatic history over the last several centuries, the understanding of near surface air temperature variability is confined to the comparatively shorter observational period (1895‐present). Here, we detail the application of blue intensity (BI) methods on a network of tree‐ring collections and examine their utility for producing robust paleotemperature estimates. Results indicate that maximum latewood BI (LWBI) chronologies exhibit positive and temporally stable correlations (r = 0.28–0.54, p < 0.01) with summer maximum temperatures. As such, we use a network of LWBI chronologies to reconstruct August‐September average maximum temperatures for the Southeast spanning the period 1760–2010 CE. Our work demonstrates the utility of applying novel dendrochronological techniques to improve the understanding of the multi‐centennial temperature history of the Southeast. Plain Language Summary: Tree‐ring data are important sources of paleoclimate information, which allow for the longer‐term evaluation of modern climate values and trends. Compared to much of North America, the Southeastern United States (Southeast) contains substantially fewer paleoclimate records from tree rings, and no estimates of past temperature variability which extend before the observational period. Employing a recently developed technique, which uses light reflectance properties of wood to obtain a representative metric of tree‐ring density, we develop a network of temperature‐sensitive tree‐ring records across the Southeast. These records enable us to reconstruct late summer maximum temperatures across the region spanning the period 1760–2023 CE. As few ground‐based, pre‐instrumental temperature records previously existed for this region, our reconstruction allows for an improved understanding of the region's multi‐centennial climatic history. Key Points: Maximum latewood blue intensity from tree rings can effectively be used to develop paleotemperature estimates for the southeastern USThe fidelity of tree‐ring density parameters for paleoclimate reconstruction are influenced by disturbance regimes and microsite conditionsCompared to the last 260 years, regional 20th‐century maximum late summer temperatures are not characterized by unprecedented positive trend [ABSTRACT FROM AUTHOR]

The Millennium Eruption of Changbaishan Volcano is heralded as one of the largest explosive eruptions in the Late Holocene and produced huge quantities of tephra. The petrogeochemical method estimates that the Millennium Eruption emitted up to 45 Tg of sulfur into the atmosphere—more than in the Tambora eruption in 1815 CE, which caused "a year without a summer" across the Northern Hemisphere in 1816 CE. Despite such massive emissions, evidence for this eruption's climate impact in East Asia remains elusive. To explain this contradiction, this study used 67 high‐resolution tree‐ring‐width records from the Northern Hemisphere spanning the past two millennia, complemented by volcanic sensitivity experiments conducted with the Community Earth System Model. Results reveal a prevailing decreasing/negative trend in the proxy records during the potential eruption period, with 945 CE marking the most notable negative anomaly, suggesting that the Millennium Eruption likely occurred in 945 CE rather than 946 CE. Sensitivity experiments, corroborated by proxy records, demonstrate that the Millennium Eruption induced substantial negative temperature anomalies at middle and high latitudes, alongside an increase in Meiyu‐Baiu‐Changma precipitation in the middle and lower reaches of the Yangtze River and southwestern Japan and a decrease in precipitation in India, northern China, and the South China Sea in the first post‐eruption year. This study offers a novel perspective on the climate impact of the Millennium Eruption, reconciling previous discrepancies regarding its climate impact. Plain Language Summary: About a thousand years ago, the Changbaishan volcano erupted with incredible force, ranking as one of the largest historical eruptions in the past 2000 yrs. Despite its size, evidence for this eruption's climate impact in East Asia has remained elusive. We delved into this mystery by examining detailed high‐resolution proxy records and performing climate model simulations. Our findings suggest that the climate effects of the eruption may have been unexpectedly strong, with the Millennium Eruption potentially occurring in 945 CE that is earlier than previously thought. The Millennium Eruption triggered notable cooling at middle and high latitudes, increased Meiyu‐Baiu‐Changma precipitation in the middle and lower reaches of the Yangtze River and southwestern Japan, and reduced precipitation in India, northern China, and the South China Sea. This research helps us understand how large volcanic eruptions can interact with other natural factors to influence our climate. Key Points: Sulfur emissions of the Millennium Eruption estimated from a petrogeochemical method are inconsistent with the signal from ice‐core samplesA consistent negative response in the high‐resolution paleoclimate records suggests a significant climate impact of the Millennium EruptionThe eruption enhanced the Meiyu‐Baiu‐Changma precipitation while diminishing precipitation in India, northern China, and the South China Sea [ABSTRACT FROM AUTHOR]

Philosophers of science have paid close attention to climate simulations as means of projecting the severity and effects of climate change, but have neglected the full diversity of methods in climate science. This paper shows the philosophical richness of another method in climate science: the practice of using paleoclimate analogues to inform our climate projections. First, I argue that the use of paleoclimate analogues can offer important insights to philosophers of the historical sciences. Rather than using the present as a guide to the past, as is common in the historical sciences, paleoclimate analogues involve using the past as a guide to the future. I thereby distinguish different methods in the historical sciences and argue that these distinctions bear on debates over whether the historical sciences can produce generalizations or predictions. Second, I suggest that paleoclimate analogues might actually be considered a type of climate model, and, as such, their use expands on common characterizations of models to include those that are full-scale, naturally occurring, and non-manipulable. [ABSTRACT FROM AUTHOR]

The paleoenvironment of shales can be reconstructed to some extent using the combinations or concentrations of elements that correlate strongly with environmental conditions. In this study, we analyzed rare earth elements (REEs), major elements, and trace elements in the marine-continental transitional shales (transitional shales for short) of the Shan 2³ submember of the Shanxi Formation in the southeastern Ordos Basin. The purpose is to deduce the paleoenvironmental conditions of the shales, encompassing paleoredox, paleoclimate, paleoproductivity, and paleo-provenance. The Shan 2³ submember comprises four sections, namely Shan 2³-1, Shan 2³-2, Shan 2³-3, and Shan 2³-4. The Ba/Al, P/Al, and Cu/Al ratios, along with biogenic barium (Babio), indicate that the paleoproductivity of the submember peaked during the Shan 2³-1 deposition and exhibited a downtrend upward in other sections. Trends in the Uau and the Ni/Co, V/Cr, U/Th, and V/Sc ratios suggest that suboxic conditions prevailed during the Shan 2³-1 deposition, with the oxidation level gradually increasing from Shan 2³-1 to Shan 2³- 4. C-value and the Sr/Cu vs. Ga/Rb cross-plot indicate a warm and arid paleoclimate during the Shan 2³-1 deposition, which transitioned to cooler, drier conditions during the deposition of other sections. Indicators sensitive to paleoclimate, such as the K/Rb and Th/U ratios, along with the ICV, PIA, and Chemical Index of Alteration (CIA), highlight elevated weathering from Shan 2³-2 to Shan 2³-4, with Shan 2³-1 exhibiting the weakest weathering during its deposition. As suggested by the REE data, the Zr/Sc vs. Th/Sr cross-plot, provenance discriminant functions, and the cross-plots of Hf vs. La/Th, Th vs. HfeCo, and PREE vs. La/Yb, the sedimentary provenance for the transitional shales of the Shan 2³ submember is of multiple origins, with significant contributions from the Upper Continental Crust (UCC). Discriminant diagrams, including those of TheCoeZr/10, TheSceZr/10, LaeTheSc, and K2O/Na2O vs. SiO2, suggest that the transitional shales of the Shan 2³ submember were primarily deposited under tectonic settings such as continental island arcs (CIAs) and passive continental margins (PCMs). [ABSTRACT FROM AUTHOR]

Aims Location Taxon Methods Results Main Conclusions Long‐term climate stability, contemporary climate and environmental heterogeneity have been linked to bird diversity patterns through their direct impacts on diversification rate, as well as through their indirect effects on plant species richness, which could also directly and indirectly affect bird diversity. This study aimed to quantitatively assess whether these potential drivers could indirectly affect bird species richness through their direct effects on the diversification rate in birds in eastern Asia.Mainland China.Birds.Using the distribution data of 1127 bird species across 320 prefecture cities in China and a phylogenetic tree of these bird species, we analysed the distribution patterns of bird species richness and diversification rate of all birds, passerine birds and non‐passerine birds, respectively. We also investigated their relationships with long‐term climate stability, contemporary climate, elevation range and plant diversity using ordinary least squares regression model and simultaneous autoregressive model. In addition, structural equation model was used to analyse whether these drivers could indirectly affect bird species richness through their direct effects on bird diversification rate.The results showed that bird species richness and diversification rate were highest in southwestern China. Additionally, diversification rate for passerine birds was higher than non‐passerine birds and all birds. Regression analyses revealed that plant species richness was the variable most associated with bird species richness and diversification rate across the three groups. Notably, results from structural equation model indicated that plant species richness, elevation range and glacial–interglacial climate change can indirectly influence bird species richness by directly affecting diversification rates.These findings emphasize the importance of considering diversification rate when understanding the geographic distribution patterns of bird diversity. The direct and indirect effects of plant species richness, elevation range and glacial–interglacial climate change on bird diversity highlight the crucial role of mountain regions with higher plant diversity and stable paleoclimate in forming and maintaining biodiversity. [ABSTRACT FROM AUTHOR]

The Aalenian–Bajocian (early Middle Jurassic) cooling event (ABCE) was a significant global climate disturbance during the Jurassic. Our analysis of sporopollen fossils from 18 mudstone and silty mudstone samples, collected from the lacustrine-terrestrial succession Xishanyao Formation in the Santanghu Basin, Northwest China, revealed a total of 191 species belonging to 53 genera. We identified an assemblage, the Cyathidites–Deltoidospora–Osmundacidites–Cycadopites assemblage, which dates to the Aalenian–Bajocian (early Middle Jurassic). This assemblage can be further divided into three subassemblages in stratigraphic order: the Cyathidites–Osmundacidites–Cycadopites subassemblage, the Cyathidites–Cycadopites–Psophosphaera subassemblage, and the Cyathidites–Deltoidospora–Osmundacidites subassemblage. We applied the Sporomorph EcoGroup (SEG) model to interpret the paleoclimate features. The sporopollen fossils indicate that the Santanghu Basin underwent a shift in vegetation types, from ground cover vegetation as the dominant form to canopy trees and then back to ground cover vegetation as the primary vegetation during the Aalenian–Bajocian. The SEG model analysis demonstrates that the CCP subassemblage is characterized by a low lowland SEG/upland SEG ratio, low wetter/drier ratio within the lowland SEG, and a low warmer/cooler ratio within the lowland SEG. These characteristics reflect the vegetation's response to the ABCE in the Santanghu Basin. [ABSTRACT FROM AUTHOR]

Salinity is a crucial property of water body and is essential for the restoration of paleoecology and paleoenvironment. However, the theoretical method of application of elemental geochemical proxies to paleosalinity reconstruction is still underdeveloped. Moreover, accurate determination and reconstruction of paleosalinity and its variation in an offshore lacustrine basin have been extremely challenging thus far. This study presents detailed elemental geochemical investigations from the Zhanhua Sag in the southern Bohai Bay Basin to reconstruct the salinity variation in the Paleogene Eocene Shahejie Formation (50.8–33.9 Ma). Based on the variation of strontium barium ratio (Sr/Ba) and boron gallium ratio (B/Ga), we determined three typical salinity types of water body: salty water (Sr/Ba>0.5, B/Ga>6), brackish water (0.2

Databases of 3D paleoclimate model simulations are increasingly used within global biogeochemical models for the Phanerozoic Eon. This improves the accuracy of the surface processes within the biogeochemical models, but the approach is limited by the availability of large numbers of paleoclimate simulations at different p CO 2 levels and for different continental configurations. In this paper we apply the Frame Interpolation for Large Motion (FILM) deep learning method to a set of Phanerozoic paleoclimate model simulations to upscale their time resolution from one model run every ∼25 million years to one model run every 1 million years (Myr). Testing the method on a 5 Myr time-resolution set of continental configurations and paleoclimates confirms the accuracy of our approach when reconstructing intermediate frames from configurations separated by up to 40 Myr. We then apply the method to upscale the paleoclimate data structure in the SCION climate-biogeochemical model. The interpolated surface temperature and runoff are reasonable and present a logical progression between the original key frames. When updated to use the high-time-resolution climate data structure, the SCION model predicts climate shifts that were not present in the original model outputs due to its previous use of widely spaced datasets and simple linear interpolation. We conclude that a time resolution of ∼10 Myr in Phanerozoic paleoclimate simulations is likely sufficient for investigating the long-term carbon cycle and that deep learning methods may be critical in attaining this time resolution at reasonable computational expense, as well as for developing new fully continuous methods in which 3D continental processes are able to translate over a moving continental surface in deep time. However, the efficacy of deep learning methods in interpolating runoff data, compared to that of paleogeography and temperature, is diminished by the heterogeneous distribution of runoff. Consequently, interpolated climates must be confirmed by running a paleoclimate model if scientific conclusions are to be based directly on them. [ABSTRACT FROM AUTHOR]

The linear calibration model is a powerful statistical tool that can be utilized to predict an unknown response variable, Y, through observations of a proxy or predictor variable, X. Since calibration involves estimation of regression model parameters on the basis of a limited amount of noisy data, an unbiased calibration slope estimation is of utmost importance. This can be achieved by means of state-of-the-art, data-driven statistical techniques. The present paper shows that weighted least-squares for both variables estimation (WLSXY) is able to deliver unbiased slope estimations under heteroscedasticity. In the case of homoscedasticity, besides WLSXY, ordinary least-squares (OLS) estimation with bias correction (OLSBC) also performs well. For achieving unbiasedness, it is further necessary to take the correct regression direction (i.e., of Y on X) into account. The present paper introduces a pairwise moving block bootstrap resampling approach for obtaining accurate estimation confidence intervals (CIs) under real-world climate conditions (i.e., non-Gaussian distributional shapes and autocorrelations in the noise components). A Monte Carlo simulation experiment confirms the feasibility and validity of this approach. The parameter estimates and bootstrap replications serve to predict the response with CIs. The methodological approach to unbiased calibration is illustrated for a paired time series dataset of sea-surface temperature and coral oxygen isotopic composition. Fortran software with implementation of OLSBC and WLSXY accompanies this paper. [ABSTRACT FROM AUTHOR]

Stellar rotation at early ages plays a crucial role in the survival of primordial atmospheres around Earth-mass exoplanets. Earth-like planets orbiting fast-rotating stars may undergo complete photoevaporation within the first few hundred Myr driven by the enhanced stellar XUV [X-rays and extreme ultraviolet (EUV)] radiation, while planets orbiting slow-rotating stars are expected to experience difficulty in losing their primordial envelopes. Besides the action of stellar radiation, stellar winds induce additional erosion on these primordial atmospheres, altering their morphology, extent, and causing supplementary atmospheric losses. In this paper, we study the impact of activity-dependent stellar winds on primordial atmospheres to evaluate the extent to which the action of these winds can be significant in the whole planetary evolution at early evolutionary stages. We performed 3D magnetohydrodynamical (MHD) simulations of the interaction of photoevaporating atmospheres around unmagnetized Earth-mass planets in the time span between 50 and 500 Myr, analysing the joint evolution of stellar winds and atmospheres for both fast- and slow-rotating stars. Our results reveal substantial changes in the evolution of primordial atmospheres when influenced by fast-rotating stars, with a significant reduction in extent at early ages. In contrast, atmospheres embedded in the stellar winds from slow-rotating stars remain largely unaltered. The interaction of the magnetized stellar winds with the ionized upper atmospheres of these planets allows us to evaluate the formation and evolution of different MHD structures, such as double bow shocks and induced magnetospheres. This work will shed light on the first evolutionary stages of Earth-like exoplanets, which are of crucial relevance in terms of planet habitability. [ABSTRACT FROM AUTHOR]

The Neoproterozoic (>1160 to ~540 Ma) sedimentary record of the Tandilia System is reorganized into eight depositional sequences based on a detailed review of published sources and new lithological observations. The main compositional attributes compiled from the studied units were used to indicate changes in lithology regarding their origin. Epiclastic sections reveal supply and sources changes through the succession. Basement detritus was dominant during the deposition of the basal sequences turning drastically to a volcanic affinity dominance. The carbonate sections, dominated by intra-basinal components, were deposited in periods of rare or restricted detrital input. The older, described as a cap-dolostone, was related to bio-induced dolomite precipitation under a deglacial to interglacial context. The younger, a carbonate ramp, reveals to have been built by microbial activity adding high levels of oxygen to seawater correlated to a global oxygenation event. Compositional changes recorded in the shallow marine deposits of Tandilia could have been intricately linked to periods of tectonic and paleo-relief configurations, favoring the detrital supply into the basin, followed by relevant episodic biogeochemical changes. This study shows that the basinal-components progression was controlled by paleoclimate and paleoenvironments associated to the extensive interval between the rupture of the Rodinia to Gondwana paleogeographical framework. [ABSTRACT FROM AUTHOR]

The Carbonate Compensation Depth (CCD) refers to the depth within the ocean where the production and dissolution rates of carbonates reach equilibrium, widely likened to the oceanic calcareous 'snowline'. The reconstruction of deep-time CCD has significant implications for understanding ocean circulation, seawater chemical conditions, sediment distribution, and the surface carbon cycle. This paper critically reviews the methods for CCD reconstruction, summarizes the driving mechanisms of the Cenozoic CCD evolution and its association with the carbon cycle, and offers insights into future directions for CCD research. CCD reconstruction has evolved over the past half century from early qualitative to quantitative methods. These methodological improvements have markedly improved the accuracy and resolution of CCD. Existing studies have indicated a general trend of the CCD deepening across major ocean basins since the Cenozoic, interspersed with a minor shallowing phase during the mid-Miocene. The variations in the CCD are primarily influenced by factors such as ocean productivity, weathering, and shelf-basin partitioning. During climate events such as the Paleocene-Eocene Thermal Maximum, the CCD exhibits pulselike fluctuations. Future research should focus on precision and quantification while integrating model simulations to further explore the correlations and response mechanisms between the CCD and the paleoclimate as well as the carbon cycle. [ABSTRACT FROM AUTHOR]

The northern Tibetan Plateau is a climatically sensitive zone influenced by monsoon and westerly winds. In summer, water vapor transport can reach Qinghai Lake and the eastern section of the Qilian Mountains; in winter, westerly winds mainly control the climate. This article compares the wet/dry changes in the region during the mid-Holocene (MH) warm period, the medieval climate anomaly (MCA), the current warm period (CWP), and the future warm period from the perspective of paleoclimate. We found that the MH warm period was mainly affected by the orbit-controlled East Asian summer monsoon, and the region showed warm and humid climate characteristics. The MCA was mainly controlled by solar radiation, and there was a warm and dry phenomenon. The CWP and the future warm period are mainly controlled by the rise in temperature caused by the increase in greenhouse gases, and the climate is becoming more arid. The wet/dry patterns in the CWP and the future warm period in the next century on the northern Tibetan Plateau are similar to those in the MCA. Continued warming will lead to the expansion of the westerly belt and a gradually humid climate. The future wet/dry changes will be more similar to the MH warm period. [ABSTRACT FROM AUTHOR]

The Early‐Middle Jurassic is one of the crucial coal‐forming geologic periods in the world and an important target for hydrocarbon exploration in the Turpan‐Hami Basin, China. The paleoenvironment and vegetation reconstruction of the Early‐Middle Jurassic have been investigated using elemental geochemistry and palynological analysis to reveal paleoclimate evolution. A total of 48 genera of pteridophyte spore and 35 genera of gymnosperm pollen were identified, and 5 palynological assemblages were longitudinally divided, which showed significant differences in geochemical behaviours. The paleoenvironment was a transition from suboxidation to anoxia and then to an oxidation environment under freshwater conditions. The paleowater in the northern Taibei Sag was deeper than that in the southern part during the Middle Jurassic, which coincided with the sedimentary background of the sublacustrine fan in the north and the shallow braided river delta in the south. The paleovegetation evolved from mixed lowland–upland forest in the Hettangian‐Toarcian, to lowland fern forest in the Aalenian‐Bajocian, to upland conifers forest in the early Bathonian, to upland Cheirolepidiaceae forest in the late Bathonian‐Callovian. The Toarcian and Bathonian‐Callovian arid climate and the Hettangian‐Pliensbachian and Aalenian‐Bajocian warm‐humid climate were responses to the continued global warming events and the intensification of the East Asian monsoon circulation, respectively. The influence of the Bathonian‐Callovian aridification event on the sedimentary response in the southern Taibei Sag will be delayed due to the gradual southward migration of the depositional centre. [ABSTRACT FROM AUTHOR]

The marine subsurface is a long-term sink of atmospheric carbon dioxide with significant implications for climate on geologic timescales. Subsurface microbial cells can either enhance or reduce carbon sequestration in the subsurface, depending on their metabolic lifestyle. However, the activity of subsurface microbes is rarely measured. Here, we used nanoscale secondary ion mass spectrometry (nanoSIMS) to quantify anabolic activity in 3,203 individual cells from the thermally altered deep subsurface in the Guaymas Basin, Mexico (3-75 m below the seafloor, 0-14°C). We observed that a large majority of cells were active (83%-100%), although the rates of biomass generation were low, suggesting cellular maintenance rather than doubling. Mean single-cell activity decreased with increasing sediment depth and temperature and was most strongly correlated with porewater sulfate concentrations. Intracommunity heterogeneity in microbial activity decreased with increasing sediment depth and age. Using a dual-isotope labeling approach, we determined that all active cells analyzed were heterotrophic, deriving the majority of their cellular carbon from organic sources. However, we also detected inorganic carbon assimilation in these heterotrophic cells, likely via processes such as anaplerosis, and determined that inorganic carbon contributes at least 5% of the total biomass carbon in heterotrophs in this community. Our results demonstrate that the deep marine biosphere at Guaymas Basin is largely active and contributes to subsurface carbon cycling primarily by not only assimilating organic carbon but also fixing inorganic carbon. Heterotrophic assimilation of inorganic carbon may be a small yet significant and widespread underappreciated source of labile carbon in the global subsurface. [ABSTRACT FROM AUTHOR]

The Mediterranean region is projected to experience severe drying trends and more extreme hydroclimate events as a consequence of anthropogenic climate change over the next century. In some places this signal may have already emerged from natural variability, but uncertainty in long-term paleoclimate reconstructions can be a significant challenge to the detection of the influence of rising CO 2 on droughts. Here we provide expanded context for recent and future hydroclimate changes with a new high-resolution (0.5 o ) spatial reconstruction of the Palmer Drought Severity Index (PDSI) using a tree-ring network that spans much of the last millennium. This network provides new perspective on the existing Old World Drought Atlas (OWDA) and allows us to characterize differences between OWDA and our reconstruction. In light of the uncertainties we identify, we also reexamine previous conclusions about the severity of recent droughts in the context of earlier centuries. We find that, in both the western Mediterranean and the Levant, recent dry periods remain the worst in at least the last 500 years, but our assessment of the significance and confidence in this finding is affected by differences in the tree-ring networks used for the reconstructions. Long millennium-length hydroclimate reconstructions in the Mediterranean do provide the opportunity to understand variability and trends in the hydroclimate of the region, but extant uncertainties arising from the existing tree-ring chronology network and methodological choices call attention to locations that require further proxy collection, chronology updates, and statistical scrutiny. [ABSTRACT FROM AUTHOR]

Forty Tertiary coals from Mukah-Balingian and Merit-Pila coalfields of the Sarawak Basin, Malaysia were investigated using bulk and molecular geochemical techniques such as proximate analysis, gas chromatography-mass spectrometry, elemental analyser, isotope ratio mass spectrometry, and inductively coupled plasma mass spectrometry to reconstruct their paleovegetation, paleoclimate, and environments of deposition. In addition, principal component analysis (PCA) of selected geochemical parameters was carried out to determine the controlling influences on the petroleum potential of the humic coals. δ13C values and the abundance of terpenoids imply the predominant contribution of angiosperms to the paleoflora. Bimetal proxies (Sr/Ba, Sr/Cu, and C-value), and δD values are generally suggestive of a warm and humid climate during the accumulation of the paleopeats. However, n-alkane proxies (Pwax, Paq, n-C23/n-C29, etc.) and polycyclic aromatic hydrocarbons (PAHs) distribution suggest that Balingian coals accumulated under relatively drier and strongly seasonal paleoclimate in the Late Pliocene. When compared with published global average abundances, the investigated coals are mostly depleted in major oxides and trace elements, suggesting peat accumulation in freshwater-influenced environments. Nonetheless, higher (> 0.5 wt%) total sulfur content in some Mukah-Balingian coals suggests some degree of epigenetic marine influence. Furthermore, the low to moderately-high ash contents of the Sarawak Basin coals indicate the presence of ombrotrophic and rheotrophic peat deposits. PCA result of selected geochemical proxies suggests that source input, paleoflora, and marine incursions are not major controlling influences on the petroleum potential. However, climatic, and depositional conditions appear to slightly influence the petroleum potential of the studied humic coals. [ABSTRACT FROM AUTHOR]

I was thrilled to receive a Lifetime Achievement Medal at the 15th International Paleolimnology Symposium (IPS) in Bariloche, Argentina (2022). I will use this opportunity to tell the story of how I stumbled into the field of paleolimnology, a discipline I had not heard of until I entered graduate school. In retrospect, I feel extremely lucky to have been able to spend the last five decades addressing interesting paleoclimate/paleoenvironment questions. Furthermore, my research and teaching have taken me to many biologically fascinating and culturally intriguing places around the world. I will also use this forum to express my gratitude to the many mentors, colleagues, students, friends, and acquaintances with whom I have collaborated throughout my career. Whatever success I have enjoyed, I attribute to my good fortune in having been able to work with numerous talented and hard-working fellow scientists. [ABSTRACT FROM AUTHOR]

The climatic adaptability of an ancient building's architecture can be studied by utilizing various scientific disciplines such as archaeology, architecture, geography, applied climatology, and paleoclimatology. By conducting studies on the religious complex of Nush-i Jan in the Malayer Plain, which dates to the Median Period, we can expand our understanding of the architectural practices during that era. This current research aims to address three main questions: 1) What were the physical components of Nush-i Jan complex that allowed it to adapt to the climatic conditions? 2) How effective were these components in addressing the aforementioned issue? And 3) What were the non-physical heating or cooling arrangements implemented in the complex? Through library and field methods, the essential data has been collected. The analysis was conducted using four software applications - AutoCAD, Climate Consultant, Ecotect, and DesignBuilder - in the energy and architecture domains. The information has been processed using a descriptive-analytical approach. The architectural components of the complex, such as its orientation towards the south with an east-west extension, high building density and height, narrow passages and courtyards, mud-brick walls, wooden beam roofs, entrance doors for most of the spaces, side windows in the eastern and southern walls, ventilators, counters at the entrances of most of the buildings, and two fire-places in the guard room of the fort, play crucial roles in utilizing solar heat and minimizing the impact of cold winds. These elements ensure that the residents' heating needs are met from May to September and partially during other months, while also addressing cooling requirements on hot days. However, additional heating sources were necessary during most hours from October to May (3153 hours in total); in other words, heating production was needed. It is possible that non-physical heating methods, like the tramrails used in the Assyrian imperial palaces, were employed by the inhabitants. Finally, the complex's climatic adaptability to the Malayer Plain, along with appropriate heating and cooling strategies, have guaranteed the residents' thermal comfort. [ABSTRACT FROM AUTHOR]

To understand the role of the East Asian summer monsoon (EASM) and the East Asian winter monsoon (EAWM) on the hydroclimate in northern Taiwan, a multiproxy study has been conducted. This study aims to achieve its goal by using micro-XRF data of Ti and sulfur (S), carbon isotopic compositions (δ13C) along with elemental concentrations of carbon (C), nitrogen (N) and S, and diatom analyses in the sediment core extracted from the Dream Lake (DL; 25°10′01.9″ N, 121°33′36.0″ E and elevation = 588 m above sea level), northern Taiwan. The radiocarbon dates revealed that the DL core covered the time interval from 4.5 to 0.4 cal kyr BP. The current records revealed wetter phases during 4.5–3.0 cal kyr BP, 2.0–1.7 cal kyr BP, and 1.0–0.4 cal kyr BP, characterized by the dominance of C3 plants in the DL catchment, increased runoff, and higher lake levels. Drier climates observed in the current study during 3.0–2.0 cal kyr BP and 1.7–1.0 cal kyr BP, marked by a reduction in C3 plants, decreased runoff, and lower lake levels. The northern Taiwan climate during the late Holocene was observed to be regulated by the interplay of EASM and EAWM. The wet climate conditions during 4.5–3.0 were due to the La Niña-like conditions, which led to a strong EASM resulting in high precipitation conditions. The dry climate conditions during 3.0–2.0 cal kyr BP have coincided with El Niño-like conditions during 3.0–2.4 cal kyr BP and a subsequently strong EAWM during 2.4–2.0 cal kyr BP. Both situations led to a reduction in precipitation in the region. Unlike the time frame from 4.5 to 3.0 cal kyr BP, wet climate conditions during 2.0–1.7 and 1.0–0.4 cal kyr BP have coincided with weak EAWM conditions, which led to an increase in precipitation in northern Taiwan. The dry climate noticed between 1.7 and 1.0 cal kyr BP appeared to be the impact of both El Niño-like conditions and strong EAWM. [ABSTRACT FROM AUTHOR]

In order to cope with the complexity and variability of the terrestrial environment, amphibians have developed a wide range of reproductive and parental behaviors. Nest building occurs in some anuran species as parental care. Species of the Music frog genus Nidirana are known for their unique courtship behavior and mud nesting in several congeners. However, the evolution of these frogs and their nidification behavior has yet to be studied. With phylogenomic and phylogeographic analyses based on a wide sampling of the genus, we find that Nidirana originated from central-southwestern China and the nidification behavior initially evolved at ca 19.3 Ma but subsequently lost in several descendants. Further population genomic analyses suggest that the nidification species have an older diversification and colonization history, while N. adenopleura complex congeners that do not exhibit nidification behavior have experienced a recent rapid radiation. The presence and loss of the nidification behavior in the Music frogs may be associated with paleoclimatic factors such as temperature and precipitation. This study highlights the nidification behavior as a key evolutionary innovation that has contributed to the diversification of an amphibian group under past climate changes. The Music frogs are revealed to possess adaptative flexibility under climate changes. Mud nests evolved as a key innovation during perennial high temperatures and precipitations but lost in certain descendants when the weather got dryer and colder. [ABSTRACT FROM AUTHOR]

Proxy-based paleoclimate reconstructions in the central Zagros region suggest the occurrence of several climatic events during the Last Glacial Maximum (LGM) to Holocene. The central Zagros region is situated in a unique transition zone between mid-latitude temperate climate in the north and sub-tropical arid climate in the south and was affected in different climatic periods by the strengthening and weakening of the Indian monsoons, the inter tropical convergence belt, the westerlies and the low-pressure systems of the Mediterranean and the Atlantic Ocean. Our results suggest that a transition occurred from dry and dusty conditions during the LGM to a relatively wetter period with higher carbon accumulation rates in the Early Holocene (11600 cal yr BP). Between 30000 and 19000 cal yr BP, cold and dry climatic conditions with the dominance of Amaranthaceae and semi-desert steppe prevailed in the region. High values of magnetic susceptibility, decrease in organic matter, and increase in allogenic elements indicate the presence of cold and dry climate in the region during the LGM. The Holocene was characterized by relatively less dry and dusty conditions, which is consistent with orbital changes in insolation that affected much of the northern hemisphere. Numerous episodes of high aeolian input spanning a few decades to millennia are prevalent during the Holocene. Dry events identified in the area occurred at 10200, 9200, 8200, 5200, 4200, 3200, 2200, and 1600 cal yr BP. Also Younger Dryas, occurred in the region 12300-11600 years ago, and it was cold and dry period with a decrease amount of pollen and increase in dust. [ABSTRACT FROM AUTHOR]

The sedimentary infill of the Quibas karstic site (Early Pleistocene, southern Spain) represents the only continuous succession with remains of continental vertebrates in Europe from pre-Jaramillo to post-Jaramillo age. The Quibas site, with a significant paleontological record, is dated between 1.1 and 0.9 Ma and offers a unique opportunity to carry out a paleoclimatic reconstruction of the time period immediately after the arrival of the first humans to western Europe. For this reason, defining the dominant sedimentary processes in the different stratigraphic units and the associated paleoenvironment is essential. The Quibas site is made up of two karstic features with two stratigraphic sequences: Quibas-Cueva, containing six lithostratigraphic units, and Quibas-Sima, which contains seven lithostratigraphic units. The detailed description and analyses of the stratigraphic sections have allowed the characterization of various autochthonous and allochthonous facies of cave deposits. Paleoclimatic proxies, inferred from sedimentological analyses, reveal a record of several alternating humid and arid phases resulting from the Early Pleistocene glacial-interglacial cycles, allowing correlation to the marine oxygen isotope record. The lowermost units (pre-Jaramillo) were deposited during a long-lasting interglacial, correlated to MIS 33–31. It was followed by an increase in aridity in the intermediate units of Quibas-Sima and uppermost unit of Quibas-Cueva (Jaramillo), revealing the beginning of a glacial period at the start of the Jaramillo subchron (1 Ma), which can be correlated to MIS 30. The upper Jaramillo and post-Jaramillo units suggest these were deposited in alternating periods of aridity and humid conditions, although less humid than the pre-Jaramillo period, probably representing the MIS 29 interglacial, the MIS 28 glacial and the MIS 27 interglacial. [ABSTRACT FROM AUTHOR]

Paleoclimate data have yielded variations with periods of ~23, ~40, and ~100 ky. Thermodynamic changes resulting from orbital eccentricity, obliquity, and precession have been ascribed as the cause of the variations although processes within the oceans and atmosphere may have too short memory to explain such variations. In this work, the dynamics of Sun‐Moon gravitation (SMG) were explored for a rotating Earth and were determined to have a long memory in magma, a mostly ignored geophysical fluid with a mass ~3,400 times that of the atmosphere plus the oceans. Using the basic motion and gravitation (including obliquity) of the Sun and the Moon, we determined that SMG‐induced magma motion could produce paleoclimatic variations with multiple periods (e.g., ~23, ~40, ~80, and ~100 ky), with considerable power for Earth's heat. Such "reproducible" power could possibly maintain an energetic Earth against collapse, radioactivity, and cooling. [ABSTRACT FROM AUTHOR]

Documenting the seasonal temperature cycle constitutes an essential step toward mitigating risks associated with extreme weather events in a future warmer world. The mid-Piacenzian Warm Period (mPWP), 3.3 to 3.0 million years ago, featured global temperatures approximately 3°C above preindustrial levels. It represents an ideal period for directed paleoclimate reconstructions equivalent to model projections for 2100 under moderate Shared Socioeconomic Pathway SSP2-4.5. Here, seasonal clumped isotope analyses of fossil mollusk shells from the North Sea are presented to test Pliocene Model Intercomparison Project 2 outcomes. Joint data and model evidence reveals enhanced summer warming (+4.3° ± 1.0°C) compared to winter (+2.5° ± 1.5°C) during the mPWP, equivalent to SSP2-4.5 outcomes for future climate. We show that Arctic amplification of global warming weakens mid-latitude summer circulation while intensifying seasonal contrast in temperature and precipitation, leading to an increased risk of summer heat waves and other extreme weather events in Europe's future. [ABSTRACT FROM AUTHOR]

CO2 absorbs and emits radiation, which allows it to act both as radiative forcing and feedback. Recent work has shown CO2's feedback effect becomes dominant in hothouse climates, giving rise to a non‐monotonic climate sensitivity around 310 K. However, CO2's feedback effect in colder climates is less clear. We use a line‐by‐line model to explore the CO2‐dependence of the longwave clear‐sky feedback and identify a dividing temperature. Above 290 K, feedback increases with CO2 concentration; below 290 K, feedback decreases with CO2 concentration. We explain this dependence in terms of spectral competition under CO2 increases. In hot climates, CO2's moderate feedback replaces near‐zero feedback from the H2O bands; in cold climates, CO2's moderate feedback replaces the large feedback from the surface. Given that global mean temperature is currently close to 290 K, our results suggest that feedback CO2‐dependence is weak at present but can be important in past and future climates. Plain Language Summary: CO2 traps heat, causing warming. But CO2 also emits heat to space, acting as radiative feedback. Recent work has shown CO2's feedback effect crucially helps to stabilize very hot climates, but how does it affect present‐day Earth? We show that in hot climates, more CO2 increases Earth's feedback, while in cold climates, more CO2 decreases it. To understand why, we explain that the surface is an effective emitter, CO2 is a moderate emitter, while H2O is a poor emitter. At high temperatures, adding CO2 to the atmosphere thus replaces feedback that would have otherwise come from H2O, increasing the overall feedback; at low temperatures, adding CO2 replaces feedback that would have otherwise come from the surface, decreasing the overall feedback. Currently, Earth's global‐mean temperature falls between these two temperature regimes, where CO2's effect on feedback is nearly zero. Our results explain why CO2's impact on feedback is small now but can be significant in past or future climates. Key Points: An increase in CO2 concentration strengthens Earth's feedback in hot climates, ∂λ/∂CO2 > 0, but weakens it in colder climates, ∂λ/∂CO2 < 0Whether feedback CO2‐dependence, ∂λ/∂CO2, is positive or negative primarily depends on the extent of the H2O windowFeedback CO2‐dependence and forcing temperature‐dependence, ∂λ/∂CO2 = −∂F2x/∂Ts, can be important for past or future climates [ABSTRACT FROM AUTHOR]

Context. Out of the more than 5000 detected exoplanets, a considerable number belong to a category called "mini-Neptunes". Interior models of these planets suggest that they have primordial H–He-dominated atmospheres. As this type of planet is not found in the Solar System, understanding their formation is a key challenge in planet formation theory. Unfortunately, quantifying how much H–He planets have, based on their observed mass and radius, is impossible due to the degeneracy of interior models. Aims. Another approach to estimating the range of possible primordial envelope masses is to use formation theory. As different assumptions in planet formation can heavily influence the nebular gas accretion rate of small planets, it is unclear how large the envelope of a protoplanet should be. We explore the effects that different assumptions regarding planet formation have on the nebular gas accretion rate, particularly by exploring the way in which solid material interacts with the envelope. This allows us to estimate the range of possible post-formation primordial envelopes. Thereby, we demonstrate the impact of envelope enrichment on the initial primordial envelope, which can be used in evolution models. Methods. We applied formation models that include different solid accretion rate prescriptions. Our assumption is that mini-Neptunes form beyond the ice line and migrate inward after formation; thus, we formed planets in situ at 3 and 5 au. We considered that the envelope can be enriched by the accreted solids in the form of water. We studied how different assumptions and parameters influence the ratio between the planet's total mass and the fraction of primordial gas. Results. The primordial envelope fractions for low- and intermediate-mass planets (total mass below 15 M⊕) can range from 0.1% to 50%. Envelope enrichment can lead to higher primordial mass fractions. We find that the solid accretion rate timescale has the largest influence on the primordial envelope size. Conclusions. Rates of primordial gas accretion onto small planets can span many orders of magnitude. Planet formation models need to use a self-consistent gas accretion prescription. [ABSTRACT FROM AUTHOR]

Reconstructing Pleistocene glaciation timing and extent is vital for understanding paleoclimate. Whereas late Pleistocene glaciation has been studied extensively in western North American mountain ranges, the glacial history of the western Elk Range in Colorado remains understudied, particularly in the East River watershed, a site of intense scientific focus. Here we use cosmogenic nuclide exposure and depth–profile dating methods to determine the timing of glaciation in the East River watershed. We use glacier modeling to reconstruct paleoglacier extents and quantify past climate conditions. Our findings indicate that the East River glacier retreated from its maximum position approximately 17–18 ka, moving to recessional positions between 13 and 15 ka, before experiencing more substantial retreat to high-elevation cirques around 13 ka. Glacier modeling suggests that the maximum ice extents at 17–18 ka could have been sustained by temperature depressions of approximately −6.5°C compared to modern conditions, assuming consistent precipitation. Additionally, the ice position at 13–15 ka could have been supported by temperature depressions of around −4.0°C. These results offer insights into the deglaciation timeline in the East River watershed and broader western Elk Range as well as paleoclimate conditions during the late Pleistocene, which may aid future research on critical zone evolution in the East River watershed. [ABSTRACT FROM AUTHOR]

Among the global monsoon systems, the Asian summer monsoon (ASM) reaches the furthest north into eastern Asia and separates it into the monsoon- and westerlies-dominated regions. Paleoclimate studies revealed different hydroclimate patterns between the monsoon- and westerlies-dominated regions at glacial-interglacial and centennial timescales. The monsoon-westerlies boundaries are difficult to be quantified with the instrumental data. Herein, a monsoon-westerlies dipole pattern was identified by empirical orthogonal function (EOF) analysis of the Palmer Drought Severity Index (PDSI) for the 1900–2018 period on interdecadal timescales. This dipole pattern showed significant correlations with variations of the monsoon-related western Pacific sea surface temperature (SST) and the westerlies-related North Atlantic Oscillation (NAO). We then reconstructed the dipole pattern back to 1511 by tree rings, which was consistent with the reconstructed NAO at interdecadal timescale. Our reconstruction revealed long-term changes of monsoon-westerlies boundaries and provided evidence of their linkages with the NAO. Apart from anthropogenic forcing, climate internal variability also play a critical role in modulations of the dipole mode between ASM and westerlies at interdecadal timescale. [ABSTRACT FROM AUTHOR]

Quantitative investigations of ancient rivers usually provide insights into either instantaneous or mean flow conditions. There is a critical gap between these time scales of investigation, which reflects the intermittency of flow and sediment transport, and closing this gap is crucial to fully explore the dynamics and evolution of ancient fluvial landscapes. Here, we combined fluvial stratigraphic data sets, flow and sediment transport models, and paleoclimate general circulation model (GCM) results to develop new methods to estimate intermittency in the geological past, specifically flow intermittency factors (Iw) and sediment transport intermittency factors (Is), and we show how they can be used to explore past hydrograph shapes. We illustrated these methods using the Upper Cretaceous Last Chance Ferron Sandstone in Utah, western United States. For sand-transporting flow conditions in Last Chance Ferron rivers, we estimated Iw values of 0.54-0.90, which imply that channel-forming conditions were sustained for the majority of the year, consistent with perennial systems in which relatively large discharges were sustained. In contrast, for gravel-transporting flow conditions, Iw values of 0.28-0.38 suggest that the largest formative flows may have occupied Last Chance Ferron rivers for nearly a third of the year, which could be explained by a monsoonal system in which high-magnitude discharge events were sustained, or a subtropical system in which high-magnitude discharge events had short durations but high frequencies. Meanwhile, Is values of 0.075-0.15 suggest that annual sediment budgets could have been transported in as little as 10 days and up to 2 months, if channel-forming conditions were sustained, and these values highlight that small changes in the duration of channelforming conditions could significantly impact sediment budgets. Our results are consistent with independent facies- and proxy-based insights into Last Chance Ferron rivers, which point to a perennially wet system characterized by a monsoonal or subtropical discharge regime. Further, our results highlight new opportunities to use paleoclimate GCMs to constrain intermittency factors in the geological past. Going forward, paleoclimate GCMs will be particularly useful where the rock record is incomplete or inaccessible, or where stratigraphic approaches are limited, and they will enable us to tackle pertinent research questions pertaining to past surface processes on both Earth and other planets. [ABSTRACT FROM AUTHOR]

Siliciclastic muds (clay-and silt-sized sediment) concentrate physical and chemical weathering products. However, both rock composition and climate can affect the mineralogy and geochemistry of these sediments. We quantitatively assessed the influence of provenance and climate on muds collected from end-member climates to test, which, if any, of these potential weathering signatures are indicative of climate in finegrained, fluvial sediments. Granulometry, mineralogy, and geochemistry of the studied muds indicated that provenance and mineral sorting hinder interpretation of (paleo)climate signals. These issues also affect chemical index of alteration (CIA) values, as well as mafic-felsic-weathering (MFW), Al2O3-(CaO* + Na2O)-K2O (A-CN-K), and Al2O3-(CaO* + Na2O + K2O)-(FeOT + MgO) (ACNK-FM) ternary plots, decreasing their utility as paleoclimate proxies. CaO content is heavily weighted within the calculations, resulting in even felsic-sourced sediment commonly plotting as mafic owing to the relative enrichment in CaO from preferential sorting of Ca-rich minerals into the mudsized fraction during transport. These results cast doubt on the indiscriminate use of CIA values and ternary plots for interpreting chemical weathering and paleoclimate within muds, particularly from glacial systems. Most notably, the positive correlations between CIA and climatic parameters (mean annual temperature and mean annual precipitation) diminished when sediments that had formed in nonglacial settings were filtered out from the data sets. This implies that CIA may only be applicable when used in nonglacial systems in which the composition of the primary source material is well constrained-such as soil/paleosol profiles. Within this end-member climate data set, CIA was only useful in discriminating hothumid climates. [ABSTRACT FROM AUTHOR]

Understanding historical soil moisture (SM) variations and their relationship with temperature in high‐latitude humid regions is essential for predicting hot droughts under widespread warming. This paper presents the first‐ever annual‐resolution summer surface SM reconstruction (1736–2006 CE) in Sweden, located in northern Europe (NE). The reconstruction utilizes the paleoclimate proxy, tree‐ring δ18O, which exhibits a strong correlation with reanalysis SM data during 1948–2007 CE (r = −0.67, p < 0.001). In contrast to an unprecedented trend suggested by previous studies, our reconstruction exhibits a wetting trend in NE since the 1960s falling within the historical spectrum of trends. Both reanalysis SM data and our reconstruction show significant negative correlations with temperature at interannual timescales. However, Coupled Model Intercomparison Project Phase 6 climate models failed to capture the significant SM‐temperature relationship during the historical (1850–1947 CE) and observation periods (1948–2006 CE). This proxy‐model comparison represents a critical step toward enhancing our understanding of SM dynamics and the reliability of SM projections in high‐latitude humid regions. Plain Language Summary: Soil moisture (SM) refers to water in any form contained in soils, and it plays an important role in sustaining plant growth and influencing climate dynamics. SM deficits can result in ecological/agricultural droughts. However, our understanding of historical SM changes is limited due to the scarcity of long‐term records. Consequently, modeling historical SM changes proves challenging and prone to inaccuracies. In this study, we utilized a tree‐ring record to reconstruct centuries‐long SM changes in Sweden, located in northern Europe. Our analysis revealed a significant negative correlation between SM and temperature in both our reconstruction and SM data sets. However, state‐of‐art models failed to capture the significant relationship observed at our study site. These findings highlight the need to improve climate models to increase the accuracy of climate forecasts and better understand SM dynamics in high‐latitude humid areas. Key Points: This study presents the first 271‐year historical soil moisture (SM) reconstruction in northern Europe (NE) using the tree‐ring δ18O proxySignificant correlations between historical SM and temperature in NE were observed at interannual timescalesOur results implied that Coupled Model Intercomparison Project Phase 6 models might underestimate the SM‐temperature relationship [ABSTRACT FROM AUTHOR]

The geochemistry of tropical coral skeletons is widely used in paleoclimate reconstructions. However, sub‐aerially exposed corals may be affected by diagenesis, altering the aragonite skeleton through partial dissolution, or infilling of secondary minerals like calcite. We analyzed the impact of intra‐skeletal calcite on the geochemistry (δ18O, Sr/Ca, Mg/Ca, Li/Mg, Li/Ca, U/Ca, B/Ca, Ba/Ca, and Mn/Ca) of a sub‐aerially exposed Porites sp. coral. Each micro‐milled coral sample was split into two aliquots for geochemistry and X‐ray diffraction (XRD) analysis to quantify the direct impact of calcite on geochemistry. We modified the sample loading technique for XRD to detect low calcite levels (1%–2%; total uncertainty = 0.33%, 2σ) in small samples (∼7.5 mg). Calcite content ranged from 0% to 12.5%, with higher percentages coinciding with larger geochemical offsets. Sr/Ca, Li/Mg, Li/Ca, and δ18O‐derived sea‐surface temperature (SST) anomalies per 1% calcite were +0.43°C, +0.24°C, +0.11°C, and +0.008°C, respectively. A 3.6% calcite produces a Sr/Ca‐SST signal commensurate with local SST seasonality (∼1.5°C), which we propose as the cut‐off level for screening calcite diagenesis in paleo‐temperature reconstructions. Inclusion of intra‐skeletal calcite decreases B/Ca, Ba/Ca, and U/Ca values, and increases Mg/Ca values, and can therefore impact reconstructions of paleoclimate and the carbonate chemistry of the semi‐isolated calcifying fluid in corals. This study emphasizes the importance of quantifying fine‐scale calcite diagenesis to identify coral preservation levels and assure robust paleoclimate reconstructions. Key Points: The modified sample loading technique adopted for X‐ray diffraction significantly reduced the uncertainty of calcite measurement down to 0.33%Temperature reconstructions based on Sr/Ca, Li/Mg, and Li/Ca are significantly affected by low levels of intra‐skeletal calcite (1%–2%)Impact of low levels of intra‐skeletal calcite on δ18O, Ba/Ca, Mn/Ca, and U/Ca is not significant [ABSTRACT FROM AUTHOR]

High‐resolution records from past interglacial climates help constrain future responses to global warming, yet are rare. Here, we produce seasonally resolved climate records from subarctic‐Canada using micron‐scale measurements of oxygen isotopes (δ18O) in speleothems with apparent annual growth bands from three interglacial periods—Marine Isotope Stages (MIS) 11, 9, and 5e. We find 3‰ lower δ18O values during MIS 11 than MIS 5e, despite MIS 11 likely being warmer. We explore controls on high‐latitude speleothem δ18O and suggest low MIS 11 δ18O values reflect greater contribution of cold‐season precipitation to dripwater from longer annual ground thaw durations. Other potential influences include changes in precipitation source and/or increased fraction of cold‐season precipitation from diminished sea ice in MIS 11. Our study highlights the potential for high‐latitude speleothems to yield detailed isotopic records of Northern Hemisphere interglacial climates beyond the reach of Greenland ice cores and offers a framework for interpreting them. Plain Language Summary: Few climate records pre‐dating the last ice age exist from high‐latitude North America, which inhibits our understanding of how regions with permafrost responded to past warming and how they might change in the future. Here, we help fill this data gap by using six speleothems (cave mineral deposits) from a cave in the Northwest Territories, Canada to produce climate records that span thousands of years during former warm periods of Earth's history. We find that speleothems that grew during an exceptionally warm super‐interglacial period 400,000 years ago have 3‰ lower oxygen isotope (δ18O) values compared to those that grew during a likely cooler interglacial 125,000 years ago. We explore potential explanations for the difference in δ18O across interglacials, and suggest that lower δ18O values during warmer periods reflect greater infiltration of cool‐season precipitation with longer annual ground thaw durations. This study highlights the importance of high‐latitude speleothems to provide detailed climate records beyond the range available from Greenland ice cores. Key Points: Long high‐latitude terrestrial climate records are rare in the Northern HemisphereHigh‐latitude speleothems can provide ultra‐high‐resolution climate records beyond the reach of Greenland ice coresMean oxygen isotopes of Arctic and subarctic speleothems likely are controlled by annual ground thaw durations [ABSTRACT FROM AUTHOR]

The Late Ordovician-Early Silurian period witnessed the Phanerozoic mass extinction, glacial events, and volcanic events. Paleoweathering indexes chemical index of alteration (CIA), chemical index of weathering (CIW), and plagioclase index of alteration (PIA) indicated that the source area weathering changed from weak to moderate to intense. CIA values in the upper Zhongbao formation ranged from 66.71% to 73.97%, indicating a drier and colder climate. Upward, the CIA values on the bottom of the Mayinggou formation returned to the high value quickly (from 73.86% to 81.31%), suggesting that the ice age ended, the climate became warmer and wetter, and the sea level rose. The Al2O3-(CaO*+Na2O)-K2O triangular plots, Hf-La/Th, and SiO2-Al2O3/TiO2 bivariate plots inferred that the source of the siltstones in the two formations is mostly from the felsic igneous rocks. The samples from the Zhongbao-Mayinggou formations have chondrite-normalized rare earth element (REE) patterns similar to that of the North Qilian volcanic arc rocks. Geochemical discrimination plots displayed that the sediments of the Zhongbao-Mayinggou formations came from the active continental margin setting. [ABSTRACT FROM AUTHOR]