Driving force behind global cooling in the Cenozoic: an ongoing mystery

The stepwise cooling marks the long-time global climate change during the Cenozoic, particularly since the Oligocene/Eocene boundary. This climatic evolution has been punctuated by several warming such as the peak Cenozoic warmth at 52 Ma, the late Oligocene warming at ～25 Ma and the Mid-Miocene Climatic Optimum at 17–14 Ma. Concurring with the global temperature changes, the Asian paleoenvironment has been modulated by the global cooling and the tectonic uplift during the Cenozoic, but what have driven the global climatic changes remains unresolved. In this review paper, I hypothesize that a threshold CO_2 level in combination with favorable orbital configuration, ocean circulation,enhanced ice albedo and possible roles of silicate mineral and basalt weathering together facilitated the development of glaciations in the Cenozoic and the past temperature change. The synchronous variations between Earth's surface temperature and atmospheric CO_2 level may indicate that the atmospheric CO_2 content is the direct driving force for the global climatic cooling, but this hypothesis needs testing by using high-resolution geological record and paleoclimatic modeling.

Linear Global Temperature Correlation to Carbon Dioxide Level, Sea Level, and Innovative Solutions to a Projected 6°C Warming by 2100

Too many climate committees, conferences, articles and publications continue to suggest a one and a half (1.5°C) to two degrees (2°C) Celsius as an achievable global limit to climate changes without establishment of any causal link to the proposed anti-warming mechanism. A comprehensive review has found instead that observationally informed projections of climate science underlying climate change offer a different outlook of five to six-degree (5°C - 6°C) increase as “most accurate” with regard to present trends, climate history and models, yielding the most likely outcome for 2100. The most causative triad for the present warming trend from 1950 to the present is identified in this paper: 1) the tripling (3×) of world population;2) the quadrupling (4×) of carbon emissions;and 3) the quintupling (5×) of the world energy consumption. This paper presents a quantitative, linear global temperature correlation to carbon dioxide levels that has great predictive value, a short temporal feedback loop, and the finding that it is also reversible. The Vostok ice core temperature and CO2 values for the past 400,000 years, with past sea level estimates have produced the sufficiently evidential “Hansen’s Graph”. Detailed analysis results in an equation for global average temperature change and an indebted, long-term sea level rise, from even a 20 ppm of CO2 change above 290 ppm, commonly taken as a baseline for levels before 1950. Comparison to the well-known 800,000 year old Dome C ice core is also performed. The best-performing climate change models and observational analysis are seen to project more warming than the average model often relied upon. World atmosphere, temperature, and sea level trends for 2100 and beyond are analyzed. A laboratory experiment proves the dramatic heat-entrapment capability of CO2 compared to pure air, which yields insights into the future global atmospheric system. Policy-relevant climate remediation, including gigaton carbon capture, zero and negative emissions and positive individual action, are reviewed and updated, with recommendations.

Paleoclimatic and provenance implications of magnetic parameters from the Miocene sediments in the Subei Basin

Thick sediments from foreland basins usually provide valuable information for understanding the relationships between mountain building,rock denudation,and sediment deposition.In this paper,we report environmental magnetic measurements performed on the Miocene sediments in the Subei Basin,northeastern Tibetan Plateau.Our results show two different patterns.First,the bulk susceptibility and SIRM,ARM,and HIRM mainly reflect the absolute-concentration of magnetic minerals;all have increased remarkably since 13.7 Ma,related to provenance change rather than climate change.Second,the ratios of IRM100mT/SIRM,IRM100mT/IRM30mT,and IRM100mT/IRM60mT,together with the redness and S ratio,reflect the relative-concentration of hematite,being climate-dependent.Their vertical changes correlate in general with the long-term Miocene climatic records of marine oxygen isotope variations,marked by the existence of higher ratios between 17 and 14 Ma.This may imply that global climate change,rather than uplift of the Tibetan Plateau,played a dominant role in the long-term climatic evolution of the Subei area from the early to middle Miocene.

Quartz grain surface microtextural evidence for provenance of the Quaternary aggradation red earth deposit, southern China

The Quaternary aggradation red earth(QARE)deposit in the middle reaches of the Yangtze River(MRYR)in southern China provides important evidence for understanding the paleoenvironment.However,its provenance remains controversial.In this study,the surface microtextures of grains from the QARE were observed,and compared with those of grains from the loess deposit on the Loess Plateau in northern China.The results show that the surface microtextures and morphologies of the quartz grains in the QARE are distinctly different from those in the northern loess,indicating that the deposits in the two regions have different provenances.The Gobi and deserts in inland northwestern China are not considered as the primary provenance for the QARE in southern China.It is suggested that the large areas of dry and bare river and lake beds and floodplains in the MRYR,which became exposed during glacial periods,provided the dominant source for materials in the QARE.We suggest that against the background of the middle-Pleistocene climate transition(MPT),regional aridification and a strengthened east Asian winter monsoon(driven by global cooling and the rapid uplift of the Tibetan Plateau)were primary drivers for the initiation of the QARE deposit in the MRYR region in southern China.The development of large areas of aeolian red earth deposit is direct evidence of environmental deterioration in the MRYR,indicating a cold and dry environment with frequent aeolian activity,in an area that now experiences a warm and humid subtropical monsoon climate.The results are also evidence of a regional response in the mid-subtropics of southern China to the MPT global cooling event around 1.2 Ma.

Solar Activity and Climate Change Hazards

This paper discusses that the global worming caused by the green-house gases effect will be equal or less than that of the global cooling resulting from the solar activities. In this respect, we refer to the MDM （Modern Dalton Minimum） which stated that starting from 2005 to the next 40 years; the earth＇s surface temperature will become cooler than nowadays. However, the degree of cooling, previously mentioned in old Dalton Minimum （c. 210 year ago）, will be minimized by building-up of green-house gases effect during MDM period. Regarding to the periodicities of solar activities, it is clear that we have a new solar cycle of around 210 years now.

The Gutian Invasion in the Middle East as a Possible Anthropogenic Trigger Factor in the Development of the 4.2 ky Event

It is commonly accepted that the current global warming is caused by humans, especially by anthropogenic emission of carbon dioxide. It is justifiably considered to be one of the biggest threats for life on the planet and human civilization. However, since millennia humans have been changing the climate locally and globally. Especially after the development of agriculture and animal husbandry people have been progressively increasing the albedo of the planet. The cooling of the climate that took place since the Neolithic Revolution and lasted until the onset of the Industrial Revolution corresponds better with the growth of human population than with any other factor. The current global warming threatens with drought, hunger, migrations and inundation of coastal areas. However, throughout the human history, it was the cooling that was related to drought and hunger. The cooling and drought that occurred about 4.2 thousand years ago (the 4.2 ky event) were the most severe. It resulted in the collapse of all Neolithic civilizations. Its reason is still not explained. This paper presents a hypothesis how people could unwillingly cause change in monsoons’ strength and direction as well as global climate catastrophe that occurred 4.2 thousand years ago.

Variations in chemical compositions of the eolian dust in Chinese Loess Plateau over the past 2.5 Ma and chemical weathering in the Asian inland

Major and trace elements as well as strontium isotopic composition have been analyzed on the acid-insoluble (AI) phase of the loess-paleosol sequence from Luochuan, Shaanxi Province, China. Results show that the chemical composition of AI phase of loess and paleosols is distinctive to the average composition of upper continental crust (UCC), characterized by depletion of mobile elements Na, Ca and Sr. The distribution pattern of elements in AI phase reveals that initial dust, derived from a vast area of Asian inland, has suffered from Na- and Ca-removed chemical weathering compared to UCC. Some geochemical parameters (such as CIA values, Na/K, Rb/Sr and87Sr/86Sr ratios) display a regular variation and evolution, reflecting that the chemical weathering in the source region of loess deposits has decreased gradually since 2.5 Ma with the general increase of global ice volume. This coincidence reflects that the aridity of Asian inland since the Quaternary is a possible regional response to the global climate change.

Innovations and stepwise evolution of CBFs/DREB1s and their regulatory networks in angiosperms

The C-repeat binding factors/dehydrationresponsive element binding protein 1 s(CBFs/DREB1 s)have been identified as major regulators of cold acclimation in many angiosperm plants.However,their origin and evolutionary process associated to cold responsiveness are still lacking.By integrating multi-omics data of genomes,transcriptomes,and CBFs/DREB1 s genome-wide binding profiles,we unveil the origin and evolution of CBFs/DREB1 s and their regulatory network.Gene collinearity and phylogeny analyses show that CBF/DREB1 is an innovation evolved from tandem duplication-derived DREBⅢgene.A subsequent event of e-whole genome duplication led to two CBF/DREB1 archetypes(CladesⅠandⅡ)in ancient angiosperms.In contrast to cold-insensitivity of Clade I and their parent DREBⅢgenes,CladeⅡevolved a further innovation in cold-sensitive response and was stepwise expanded in eudicots and monocots by independent duplications.In geological time,the duplication events were mainly enriched around the Cretaceous-Paleogene(K-Pg)boundary and/or in the Late Cenozoic Ice Age,when the global average temperature significantly decreased.Consequently,the duplicated CBF/DREB1 genes contributed to the rewiring of CBFs/DREB1 s-regulatory network for cold tolerance.Altogether,our results highlight an origin and convergent evolution of CBFs/DREB1 s and their regulatory network probably for angiosperms adaptation to global cooling.

Enhanced weathering input from South Asia to the Indian Ocean since the late Eocene

nhanced silicate weathering induced by the uplift of the Himalayan-Tibetan Plateau(HTP)has been considered as the major cause of pCO_(2) decline and Cenozoic cooling.However,this hypothesis remains to be validated,largely due to the lack of a reliable reconstruction of the HTP weathering flux.Here,we present a 37-million-year record of the difference in the seawater radiogenic neodymium isotopic composition(△ε_(Nd))of Ocean Drilling Program(ODP)sites and Fe-Mn crusts between the northern and central Indian Ocean,which indicates the contribution of regional weathering input from the South Asian continent to the Indian Ocean.The results show a long-term increase in △ε_(Nd) and thus provide the first critical evidence of enhanced South Asian weathering input since the late Eocene.The evolution coincided well with major pulses of surface uplift in the HTP and global climatic transitions.Our foraminiferal eNd record suggests that tectonic uplift and silicate weathering in South Asia,especially in the Himalayas,might have played a significant role in the late Cenozoic cooling.

Convergent evolution of AP2/ERF Ⅲ and IX subfamilies through recurrent polyploidization and tandem duplication during eudicot adaptation to paleoenvironmental changes

Whole-genome duplication(WGD or polyploidization)has been suggested as a genetic contributor to angiosperm adaptation to environmental changes.However,many eudicot lineages did not undergo recent WGD(R-WGD)around and/or after the Cretaceous-Paleogene(K-Pg)boundary,times of severe environmental changes;how those plants survived has been largely ignored.Here,we collected 22 plants from major branches of the eudicot phylogeny and classified them into two groups according to the occurrence or absence of R-WGD:12 R-WGD-containing plants(R-WGD-Y)and 10 R-WGD-lacking plants(R-WGD-N).Subsequently,we identified 496 gene-rich families in R-WGD-Y and revealed that members of the AP2/ERF transcription factor family were convergently over-retained after R-WGDs and showed exceptional cold stimulation.The evolutionary trajectories of the AP2/ERF family were then compared between R-WGD-Y and R-WGD-N to reveal convergent expansions of the AP2/ERF Ⅲ and IX subfamilies through recurrent independent WGDs and tandem duplications(TDs)after the radiation of the plants.The expansions showed coincident enrichments in-times around and/or after the K-Pg boundary,when global cooling was a major environmental stressor.Consequently,convergent expansions and co-retentions of AP2/ERF Ⅲ C-repeat binding factor(CBF)duplicates and their regulons in different eudicot lineages contributed to the rewiring of cold-specific regulatory networks.Moreover,promoter analysis of cold-responsive AP2/ERF genes revealed an underlying cis-regulatory code(G-box:CACGTG).We propose a seesaw model of WGDs and TDs in the convergent expansion of AP2/ERF Ⅲ and IX genes that has contributed to eudicot adaptation during paleoenvironmental changes,and we suggest that TD may be a reciprocal/alternative mechanism for genetic innovation in plants that lack WGD.