Secondary minerals on Mars, particularly iron oxides, record the oxidative evolution of the planet. However, the origin and timing of large-scale oxidation of the Martian surface remain poorly constrained. Here we investigate the aqueous alteration of fayalite-forsterite (Fa100-Fa0) olivine solid solutions under a 1-bar CO2 atmosphere at 45 °C. We show that Fe-rich olivine exhibits enhanced yet non-linear dissolution behavior relative to Mg-rich forsterite, and that weathering proceeds through two stages: an initial stage (0–3 days) characterized by rapid dissolution and cation release, followed by a prolonged stage (4–180 days) dominated by Fe(III) precipitation. Alteration products are primarily Fe-enriched, Mg-depleted amorphous silicate gels, consistent with precursors to phyllosilicate formation on Mars. Crystalline Fe(III) oxides (hematite and goethite) form exclusively in the most Fe-rich systems (Fa71 and Fa100), indicating that Fe(II) oxidation can occur through water-mediated redox pathways effectively even under anoxic CO2 atmosphere. However, the abundance of Fe oxides produced in our experiments is substantially lower than the 6–20 wt.% ferric phases observed on the Martian surface, suggesting that Fe-rich olivine weathering under CO2 alone cannot account for the global ferric inventory. Despite their limited abundance, these early-formed Fe(III) oxides may have acted as catalytic nuclei, facilitating subsequent oxidation processes involving other redox-active species. Our results suggest that the earliest ferric oxides on Mars could have formed locally within Fe-rich crustal terrains under CO2-dominated conditions, initiating spatially heterogeneous but progressively amplified oxidative evolution on early Mars.

Determining when crop-derived carbon begins to accumulate in soils is critical for understanding the dynamics of large-scale agricultural expansion. However, in Northeast China, the absence of long-term, continuous, and precisely dated records of crop-derived carbon inputs into soils has hindered a clear reconstruction of regional agricultural development, particularly in tracing the eastward spread of millet agriculture from the core area of the Hongshan Culture. This study presents accelerator mass spectrometry 14C dating results from sixteen black soil sections of Northeast China, providing well-constrained ages for the initial input of crop-derived carbon. Analysis of environmental proxies—including soil organic carbon isotope, lightness, total organic carbon content, and magnetic susceptibility—reveals three distinct phases of intensified C4 crop (predominantly millet) cultivation extending eastward from the Hongshan Culture core region at approximately 7–6 ka, 4–3 ka, and 1.5–1.0 ka. This was followed by the later emergence of C3 crop cultivation, such as wheat, around 1.0 ka and 0.4 ka. The asynchronous west-to-east pattern of agricultural expansion corresponds closely with agricultural activities documented in regional archaeological records. Overall, these findings indicate that the eastward spread of C4 crops from the Hongshan Culture core region commenced around 6 ka. This research contributes to a deeper understanding of large-scale agricultural expansion by providing an essential empirical case study.

Carbon is one of the most pivotal elements on Earth, whose behavior exerts profound influences on the operation of the global climate system, the origin and evolution of life, and the formation of fossil energy resources. Over 99% of Earth's carbon resides within solid reservoirs, including sediments, crust, mantle, and core. Less than 1% is distributed among fluid reservoirs, encompassing the biosphere, oceans, and atmosphere. Oceanic plate subduction transports substantial shallow-sourced carbon-bearing materials, including sediments, altered oceanic crust, and serpentinized peridotite, into the deep mantle. Some of this subducted carbon is returned to the hydrosphere or atmosphere via mantle wedge melting and arc volcanism, wheras the rest is either stored within the lithosphere or conveyed into the deeper convective mantle. Therefore, oceanic plate subduction plays a critical role in the exchange between solid and fluid carbon reservoirs. Marine sediments overlying the oceanic crust, which are characterized by low density, weak rheological strength, and enrichment of incompatible elements, constitute a major solid carbon reservoir. This study synthesizes recent advancements and unresolved issues in our understanding of deep carbon cycling within subduction zones, including decarbonization mechanisms, the efficiency of carbon release, numerical modeling approaches, and associated climatic feedbacks. Analysis of modern subduction zone sediments reveals that trench sediments in low-latitude regions exhibit elevated carbonate content, potentially attributable to warmer seawater temperatures and enhanced pelagic organism productivity that facilitate carbonate burial in these regions. Only a fraction of subducted carbon (similar to 30%) is liberated to the atmosphere via volcanic degassing after sediments enter the trench. Following subduction, decarbonation of carbonaceous sediments occurs through metamorphic reactions, dissolution, partial melting, and diapirism of carbon-bearing material, though the relative contributions and efficiencies of these mechanisms remain debated. The decarbonation style and efficiency are primarily controlled by the protolith composition of subducted sediments and thermal structure of subduction zones. In addition, the regulatory role of water in decarbonation processes within subduction zones is also crucial. On the one hand, water addition substantially lowers the reaction temperature for carbonate decomposition. Typically initiated above 700 degrees C, the decarbonation reaction can occur at 400-600 degrees C in a hydrous environment, thus enhancing the reaction efficiency. On the other hand, water facilitates the formation of supercritical CO2-H2O fluids or carbonate melts, which serve as vital carriers for carbon transfer from the slab to the mantle wedge or the forearc crust. Numerical modeling results indicate that sediment-derived melts generated by slab heating migrate buoyantly through the mantle wedge to form diapiric structures, a critical mechanism of slab decarbonation. Plate reconstructions show that the Neo-Tethyan subduction zone persisted in low-latitude regions over prolonged geological timescales, facilitating the widespread deposition of carbonate-rich sediments due to elevated pelagic productivity and sedimentation rates near the equator. We suggest that intense magmatism induced by the subduction of these carbon-enriched sediments during the Neo-Tethyan closure may have significantly contributed to Cretaceous-Paleogene hothouse climate. Future research priorities may include the (1) development high-resolution plate reconstruction models to better constrain sediment thickness distributions over geologic time and their linkages to long-term climate change; (2) integration of experiment rock physics results with dense-array magnetotelluric and seismic observations to better image deep carbon storage within subduction zones; and (3) advancement of numerical simulation methods based on two-phase flow dynamics, enabling high-resolution modeling of sediment subduction. This will elucidate the migration and enrichment patterns of carbon-bearing materials released from the subducting slab.

The impact of the El Ni & ntilde;o-Southern Oscillation (ENSO) on East Asian summer monsoon (EASM) precipitation under sustained warming remains uncertain. Through Pliocene-like simulations, we demonstrate that under a permanent El Ni & ntilde;o-like phase, an eastward-shifted Walker Circulation triggered a low-level anticyclone over the South China Sea and prompted a southward shift of the westerly jet via a Rossby wave train. This circulation configuration facilitated the influx of abundant moisture into East Asia, consequently enhancing regional precipitation, particularly in southern China. In contrast, under a permanent La Ni & ntilde;a-like phase, a westward-intensified Walker Circulation generated a low-level cyclone over the East China Sea and a coastal anticyclone, strengthening moisture transport into East Asia, with the most pronounced increases in precipitation occurring in central-eastern China. We attribute the consistent wetting trends in East Asia across both ENSO phases to the increased moisture-holding capacity of a warmer atmosphere, which enhances rainfall efficiency irrespective of differing circulation patterns. Our findings indicate a paradigm shift in the El Ni & ntilde;o/La Ni & ntilde;a-monsoon relationship, transitioning from the contemporary dipole/tripole precipitation response to a regime in which both ENSO phases result in a broad, monopole-like increase in East Asian rainfall in a warming climate. This suggests a weakened El Ni & ntilde;o/La Ni & ntilde;a influence on the EASM precipitation under Pliocene-like warming conditions. These evolving El Ni & ntilde;o/La Ni & ntilde;a-monsoon dynamics must be considered when interpreting proxy records from past warm periods and projecting future climate impacts.

Earth's obliquity is a key palaeoclimatic parameter that regulates hemispheric seasonality and the latitudinal distribution of incoming solar radiation. However, its role in modulating global climate patterns during the warm Pliocene remained poorly constrained. To isolate the climatic impact of obliquity, we conducted a pair of idealized simulations using the HadCM3 climate model under Pliocene boundary conditions, prescribing maximum (24.5°) and minimum (22.1°) obliquity states. The results demonstrated that extreme obliquity variations drove a substantial reorganization of the global climate system through coupled radiative and dynamical processes. In the annual mean, increased obliquity produced pronounced high-latitude warming and low-latitude cooling, reflecting an amplified seasonal cycle and strong polar amplification. The resulting changes in the meridional temperature gradient induced a hemispherical asymmetric atmospheric circulation response, characterized by a poleward shift and weakening of the Northern Hemisphere jet stream and a concurrent strengthening of the Southern Hemisphere jet. These circulation adjustments strongly regulated the hydrological response, leading to a systematic northward displacement of the Intertropical Convergence Zone (ITCZ) and a poleward expansion of Northern Hemisphere summer monsoon area. The simulated climate patterns—marked by strong high-latitude temperature signals and globally coordinated circulation changes—provided a mechanistic explanation for the prominence of the 41-kyr obliquity cycle observed not only in deep-sea δ18O archives but also in high-latitude terrestrial records.

As anthropogenic carbon emissions continue to rise, global temperatures are experiencing unprecedented increases. In response to the looming threats of climate change, the Paris Agreement proposed the goal of limiting global warming to 1.5-2.0 degrees C and advocated for global emission reductions. However, recent studies suggest that even if these targets are met, internal feedback mechanisms within the climate system could still propel global warming beyond critical thresholds, potentially shifting Earth's climate from cyclical glacial-interglacial alternation to a hothouse state. Notably, 2024 was the hottest year on record, with the global average surface temperature 1.55 degrees C higher than pre-industrial levels, making it the first calendar year since the Industrial Revolution to exceed 1.5 degrees C of warming. If the current warming trend observed in recent decades continues, the Earth's average temperature could reach 20 degrees C by similar to 2300, resulting in a permanent hothouse state. This alarming prospect raises concerns within both the scientific community and the general public about the potential for catastrophic outcomes. The Cretaceous-Paleogene period represents Earth's most recent prolonged hothouse state, characterized by sustained high temperatures and elevated atmospheric CO2 concentrations. Understanding this period offers critical insights into future climate scenarios. This study synthesizes current knowledge of the Cretaceous-Paleogene hothouse Earth, exploring its driving mechanisms, environmental characteristics, ecological responses, and ultimate termination. Key findings include: (1) through integrated analysis of carbon emission patterns from mid-ocean ridges, continental rifts, large igneous provinces, and continental arcs, coupled with paleoclimatic records, we propose that continental arc magmatism was likely the primary driver of the Cretaceous-Paleogene hothouse conditions. (2) Multiple episodes of carbon cycle perturbations, lasting 10(4)-10(5) years, characterized the hothouse climate regime, driving rapid climatic warming events. These include the Cretaceous Oceanic Anoxic Events (OAEs) and the Paleogene hyperthermal events (e.g., the Paleocene-Eocene Thermal Maximum (PETM)). The OAEs are characterized by extensive black shale deposition, with distinct positive carbon isotope excursions observed during OAE1a, OAE1d, and OAE2, while OAE1b is marked by a notable negative excursion. In contrast, the Paleogene hyperthermal events consistently exhibit negative carbon isotope excursions with limited black shale deposition. This pronounced dichotomy in geochemical signatures and depositional patterns between these events can be primarily explained by fundamental differences in both the nature of carbon sources and the underlying perturbation mechanisms. (3) Hyperthermal events, characterized by pronounced negative carbon isotope excursions, occurred during prolonged periods of warming, indicating increased vulnerability of Earth's surface organic carbon reservoirs to increases in global temperature. OAE1b, PETM, and subsequent Eocene hyperthermal events were likely triggered by perturbations in these reservoirs, highlighting the necessity for comparative studies on their respective carbon emission fluxes and associated environmental impacts. (4) The hyperthermal events were associated with intensified hydrological cycles, characterized by enhanced high-latitude precipitation and complex spatial variability in mid-to low-latitude rainfall patterns. (5) The hothouse climate facilitated the expansion and diversification of thermophilic plant groups, promoting the spread of forest from low to middle and high latitudes and enhancing terrestrial plant diversity. In marine environments, there was also an increase in the diversity of dinoflagellate cysts, calcareous nannofossils, and planktic foraminifera. This synthesis highlights that the Cretaceous-Paleogene hothouse state was fundamentally maintained by deep Earth carbon emissions, while its termination was governed by carbon sequestration through enhanced chemical weathering and organic matter burial. However, significant uncertainties remain regarding quantitative carbon fluxes, spatial patterns of hydrological changes, and ecosystem responses to rapid warming. Future research directions should emphasize integrated Earth system approaches to better constrain these critical aspects of hothouse Earth dynamics.

The discrepancies between model simulations and proxy reconstructions of global mean annual temperatures since the mid-Holocene warrant further investigation. Here, we present a high-resolution pollen record from Lake Ximenlongtan (XMLT) in the Hengduan Mountains, southwestern China, precisely dated to similar to 9.4-0 ka. The results show that tropical monsoon montane rainforest, characterized by the dominance of tropical and subtropical evergreen broadleaved trees, flourished around the lake during 9.4-5.5 ka. A notable vegetation shift occurred during 5.5-5.0 ka, when tropical taxa declined and subtropical taxa increased. This transition was followed by a reduction in both tropical and subtropical evergreen taxa until similar to 4.0 ka, indicating distinct cooling during 5.5-4.0 ka. Deciduous broadleaved trees and grasses expanded during this interval, indicating a pronounced drying trend. A spatial synthesis of published data from across the Hengduan Mountains revealed a significant ecological shift during 5.5-4.0 ka, characterized by the progressive loss of warmth-adapted trees and an expansion of cold-tolerant and drought-tolerant plants. This synthesis indicates the cooling-induced weakening of the Asian summer monsoon during the mid-Holocene. The compelling evidence from this low-latitude mountainous region strongly supports the proxy-based paradigm of a mid-Holocene cooling transition, and underscores the robust positive relationship between temperature and summer monsoon intensity, which is the key to predicting future monsoon behavior.

Current methodological limitations in soil chronology constrain our understanding of soil carbon dynamics and the carbon stabilization mechanisms. Here, new 14C measurements and chemically extracted data revealed that H2O2-resistant residues effectively represent the recalcitrant carbon pool in closed soil systems. Therefore, these soils were used to establish a methodological framework for quantifying the 14C age offset between bulk soil and recalcitrant carbon fraction on a large scale. The initial time of carbon input in closed non-permafrost soils, defined by bulk-soil age plus the age offset, revealed that global soil formation accelerated synchronously with insolation-induced biome expansion approximately 12,000 years ago, with a mean age of 5255 years. The postglacial development of non-permafrost soils increased both arable land and pastoral resources, enabling population growth. Our findings confirm that organic carbon in deep-aged soils exhibits thermal inertia, whereas plant-derived particulate organic carbon within surface horizons drove decadal soil carbon accumulation under thermal forcing during the Holocene. This study has implications for refining climate projections and developing carbon sequestration strategies.

The early Eocene was marked by a series of rapid global warming events known as hyperthermals, offering insights into the planet’s biogeochemical responses to extreme climate conditions. While increased terrestrial methane (CH4) cycling has been recorded during the Paleocene−Eocene thermal maximum (PETM; ca. 56 Ma), investigations into terrestrial CH4 cycle perturbations during subsequent smaller-magnitude hyperthermals have been lacking. Consequently, the question of whether all hyperthermals exhibited a common terrestrial CH4 feedback remains unanswered. The Fushun coal seam, a recently characterized expanded wetland deposit in northeast China, preserves records of four early Eocene hyperthermals, presenting a unique opportunity to study CH4 cycling responses to varying degrees of elevated warming. Here, we employed biomarkers to reconstruct wetland CH4 cycling within the terrestrial succession. Our findings indicate a significant strengthening of microbial CH4 cycling during all hyperthermals, as evidenced by a high 3β-methylhopane index and highly negative hopane δ13C values (<−45‰). These results suggest that wetland CH4 emissions possibly acted as a common positive feedback mechanism during each hyperthermal event, sustaining elevated temperature levels. Furthermore, our data suggest a scaling of methane-climate feedback with the magnitudes of carbon isotope excursions, with more dramatic carbon cycle perturbations likely amplifying CH4 cycle intensity and, consequently, CH4 fluxes.

The Guttenberg Carbon Isotope Excursion (GICE) is the second significant positive excursion event during the Ordovician, accompanied by climatic change. However, the availability of highly precise geochronology directly associated with the GICE is lacking, impeding its comprehensive understanding. Here, S13Ccarb chemostratigraphy is reconstructed to identify the GICE at the Upper Ordovician Yangjikan section in the Tarim Basin, Northwest China. Additionally, we provide the first high-precision-U-Pb zircon chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) age of 453.29 +/- 0.15 Ma (2a analytical uncertainty) for a K-bentonite layer at the Yangjikan section. This date constrains the timing of the GICE in the Tarim Basin and indicates its synchronization with GICE records in South China and North America. Furthermore, the occurrence of the GICE coincided with contemporaneous rises in sea level for these regions, potentially suggesting that enhanced primary productivity and subsequent increased organic carbon burial have driven the GICE.

The Middle Miocene Climatic Optimum (MMCO, ca. 17.0 to 14.7 million years (Myr) ago) is a period of global warming that could be relevant to future projections for 2100 AD. However, the mechanism of atmospheric CO2 removal during this interval, particularly, whether silicate weathering is critically involved, is currently unclear. In this study, a well-dated silicate weathering record of a red clay section in East Asia during the 19.8-12.8 Myr ago interval was reported, and the silicate weathering intensity from <5 mu m fraction samples was used to minimize grain-size effects when tracing the Miocene weathering history. The results show an increase in the intensity of silicate weathering in East Asia during the MMCO. The reported data and previously published records indicate that continental weathering was enhanced in East Asia and potentially elsewhere during the MMCO, which triggered the termination of the climatic optimum.

Knowledge of glacial‐interglacial changes in the Indian summer monsoon (ISM) can provide insights into future hydrological changes in the monsoon region. We analyzed the grain size, branched glycerol dialkyl glycerol tetraethers (brGDGTs), and leaf wax hydrogen isotopes (δD wax ) of sediments from Lake Tianchi in the ISM region, to reconstruct the temperature and monsoon history for the past 23 kyr. The results reveal a notable negative correlation between the abundance of brGDGT‐IIIa and grain size, indicating the non‐negligible influence of soil‐derived brGDGTs on temperature. Using the grain size‐brGDGT‐IIIa relationship, we assessed the contribution of soil‐derived brGDGTs and corrected the temperature accordingly. The results reveal a ∼6°C warming from the Last Glacial Maximum (LGM; 23–20 kyr) to the mid‐Holocene (∼8–6 kyr), punctuated by several millennial‐scale events, including Heinrich event 1 (H1; 16.5–15 kyr), the Bølling‐Allerød (B/A; 15–12.8 kyr), and the Younger Dryas (YD; ∼12.8–11 kyr), with H1 being the coldest interval. The δD wax records show that H1 was the driest interval, with a drier LGM and YD and a wet B/A and early‐ to mid‐Holocene. Furthermore, the δD wax records display a pattern of variation similar to the interhemispheric temperature gradient, indicating that the intensity of this gradient is the primary factor controlling the ISM precipitation. Given the significant influence of Antarctic ice on the interhemispheric temperature gradient, the anticipated loss of half of the Antarctic sea ice by 2100 would lead to the southward shift of the Intertropical Convergence Zone and associated drought in the ISM region.

Geochemical records from loess-paleosol deposits offer valuable insights into past paleoclimate and paleoecological changes. Here we explore the potential of mercury (Hg) stable isotopes to study the changes of paleoprecipitation and paleovegetation and their causal effect on terrestrial Hg accumulation on the Chinese Loess Plateau (CLP). We first document how variations of Hg concentrations, Δ199Hg and Δ200Hg isotope signatures in modern soils and loess are controlled by coupled precipitation-vegetation gradients on the CLP, and unaltered by postdepositional processes. Increased precipitation promotes vegetation growth and foliar gaseous elemental Hg uptake, lowering Δ199Hg and Δ200Hg in modern soils and loess. Similar to modern soils and loess, we attribute Hg accumulation and isotope signatures in loess-paleosol deposits to changes in vegetation Hg uptake in response to variation in paleoprecipitation. Both modern and paleo loess and soils suggest faster Δ199Hg changes and Hg accumulation to precipitation under high precipitation conditions (e.g., > 500 mm yr-1) than under arid conditions, reflecting their potential as proxies for pronounced wet and dry climate changes in the CLP. Our results evidence enhanced sequestration of atmospheric Hg emissions in loess soils during interglacial wetter periods. Warming and changes in precipitation patterns in response to global climate change may therefore lead to enhanced Hg burial in soils.

Early Eocene hyperthermal events, including the Paleocene-Eocene Thermal Maximum (PETM) and subsequent events (ETM2/H1, H2, and I1), provide critical insights into vegetation and carbon cycle responses to extreme warming during the Early Eocene. Here, we present multiproxy biomarker records and compound-specific delta 13C data from the Fushun Basin in Northeast China, systematically reconstructing the vegetation dynamics and carbon flux changes during these hyperthermals. We focused on gymnosperm-derived diterpenoids and angiosperm-derived triterpenoids as tracers of floral response. During the PETM, gymnosperms experienced a transient surge in vegetation carbon flux, in contrast to angiosperms, which exhibited a persistent decline across all hyperthermal phases. This challenges the conventional paradigm of gymnosperm vulnerability to warming. Concurrently, Climate change has induced complex alterations in vegetation composition. Compound-specific delta 13C analysis revealed a significant negative carbon isotope excursion (CIE) in diterpenoids during the PETM, comparable to that of total organic carbon (delta 13CTOC), suggesting that climate intensity, rather than vegetation shifts, drove isotopic fractionation. These findings highlight the differential responses of gymnosperms and angiosperms to hyperthermals, with gymnosperms dominating carbon flux during the PETM. Our study emphasizes the role of the magnitude of climate change in modulating vegetation carbon fluxes and isotopic fractionation, highlighting the need to consider plant physiological adaptations under extreme climatic conditions to understand carbon cycle dynamics.

AbstractThe Paleocene–Eocene Thermal Maximum (PETM; ∼56 Ma) was a period of extreme global warming associated with a massive influx of isotopically light carbon into the ocean–atmosphere system. The burning of Paleocene peatland (wildfire hypothesis) has been proposed as a potential light carbon source. In addition, numerical models have predicted that wildfire activity would intensify in response to CO2‐induced global warming. In this study, we tested the wildfire hypothesis and model prediction by tracing the wildfire history across the PETM in East Asia using polycyclic aromatic hydrocarbons (PAHs). The PAH record exhibited notable spatiotemporal heterogeneity, indicating that wildfire activity varied widely across different regions and time periods during the PETM and highlighting the complex interplay between climate, vegetation, and fire dynamics. Global wildfire records do not support the global burning of Paleocene peatland; therefore, a wildfire‐related light carbon source requires close scrutiny.

Geologic records support a short-lived carbon release, known as the pre-onset excursion (POE), shortly before the Paleocene-Eocene Thermal Maximum (PETM; ~ 56 Ma). However, the source and pace of the POE carbon release and its relationship to the PETM remain unresolved. Here we show a high-temporal-resolution stratigraphic record spanning the POE and PETM from the eastern Tethys Ocean that documents the evolution of surface ocean carbon cycle, redox and eutrophication, confirming the global nature of the POE. Biomarkers extracted from the sedimentary record indicate a smaller environmental perturbation during the POE than that during the PETM in the eastern Tethys Ocean. Earth system modeling constrained by observed δ13C and pH data indicates that the POE was driven by a largely thermogenic CO2 source, likely associated with sill intrusions prior to the main eruption phase of the North Atlantic Igneous Province and possibly biogeochemical feedbacks involving the release of biogenic methane.

Lakes are critical sentinels of climate change, yet their responses to rapid warming remain poorly understood. Here we present organic geochemical data of lacustrine sediments from eastern China during the Paleocene-Eocene Thermal Maximum (56 million years ago) to unravel environmental and biotic responses to rapid warming. Organic geochemical proxies indicate >= 7 degrees C continental warming in East Asia, triggering cascading effects including intensified stratification, bottom-water deoxygenation, eutrophication, and methanogenesis. These processes, evidenced by isotopic, productivity, and redox proxies, parallel modern lake responses to anthropogenic forcing. During the Paleocene-Eocene Thermal Maximum, elevated methane emissions from lacustrine systems likely amplified warming through positive carbon-cycle feedbacks. Our findings highlight lakes as one of potential dynamic amplifiers of carbon cycle perturbations, providing critical insights into freshwater ecosystem resilience in a warming world. This deep-time perspective underscores the vulnerability of modern lakes to cascading ecological disruptions, informing models of ecosystem resilience and carbon-climate interactions under sustained warming.

Recent increases in carbon emissions have driven global temperatures upward, significantly elevating wildfire risks and posing substantial challenges to ecosystems. The Mid-Cretaceous (110~82Ma) and Early Paleogene (56~47Ma) periods represent two characteristic hothouse periods that serve as crucial geological analogs for understanding potential future extreme climates and their ecological impacts. This study examines the Cretaceous-Paleogene hothouse period by compiling fire event proxies, including black carbon records, to analyze paleofire characteristics and their relationship with hothouse environments. We conduct a comparative analysis of paleofire patterns between these two periods and investigate their underlying controlling factors. Our key findings reveal: (1) Fire events were predominantly concentrated in the mid-latitude regions of the Northern Hemisphere during both hothouse periods, with geological evidence and climate modeling suggesting that pronounced seasonal climate variations in these regions facilitated fire occurrences; (2) The Cretaceous hothouse period experienced more frequent fire events compared to the Paleogene hothouse period; (3) Elevated temperatures and atmospheric oxygen levels during the Cretaceous hothouse period created favorable conditions for fire activity, while changes in vegetation composition and reduced climatic seasonality during the Paleogene hothouse period suppressed fire occurrence. Future research should prioritize the comprehensive analysis of fire proxies, the development of deep-time paleofire databases, and the assimilation of paleoclimate data to advance understanding of the coupled interactions among fire regimes, vegetation dynamics, and hothouse climates. Such efforts will provide critical insights for projecting future wildfire trends and ecological responses under sustained global warming.

Human civilization's evolution is shaped by climate change, with solar energy input into the Earth's system as the primary external driver. This influence should be more pronounced during agricultural stages and periods of extreme solar activity. The late Joseon Dynasty of Korea serves as an ideal civilization sample of political continuity and stability, maintaining a 285-year-long meteorological diary and rainfall records with a temporal resolution of up to 2 hours, perfectly encompassing the Maunder Minimum (MM). Here we quantitatively reconstruct the rainfall patterns, revealing a rare, nearly century-long drought around the MM, accompanied by decadal climate fluctuations correlated to the sunspot cycle. Quantitative socio-environmental analyses further indicate that the convergence of cold, arid conditions and heightened climate instability ultimately precipitated cascading ecological and societal crises during the late Joseon Dynasty. Our findings offer new perspectives for understanding and addressing the impacts of future periods of extreme solar activity on modern civilization.

The mid-Cretaceous (100 similar to 80Ma) to early Paleogene (56 similar to 47 Ma) represents the most recent and prominent greenhouse interval in Earth's history, characterized by markedly elevated surface temperatures and persistently high atmospheric CO2 concentrations. However, its deep Earth driving mechanisms remain inadequately constrained. Through a systematic synthesis and analysis, this study finds that carbon emissions from mid-ocean ridges, large igneous provinces (LIPs), and continental rift systems-although significant-exhibit limited temporal coupling with the major greenhouse phases during this interval. In contrast, low-latitude continental arcs exhibit distinctly high-carbon characteristics, rendering them disproportionately important contributors to global deep carbon emission. Our compiled evidence suggests that continental arcs situated within the low-latitude Neo-Tethyan tectonic domain (Kohstein-Ladakh-Gangdese-Lohit-Sumatra) -experienced two major magmatic flare-ups during the Late Cretaceous (ca. 100 similar to 80Ma) and Early Eocene (ca. 52 similar to 48Ma). This period was accompanied by massive CO2 emissions (with estimated carbon fluxes of 0.9 similar to 3. 15Tmol/yr during the Cretaceous and 5.94Tmol/yr during the Paleogene), which likely played a pivotal role in driving and sustaining the Cretaceous-Paleogene greenhouse climate. This mechanism significantly advances our understanding of the coupling between deep carbon cycling and surface climate systems, and provides a new conceptual framework for interpreting the origin of extreme climatic events in Earth's history. It also underscores the need to further investigate low-latitude continental ares as critical deep carbon sources in long-term climate regulation.