Paleoanalogues of global warming in the 21st century

On the basis of landscape-climatic reconstructions for warming periods in the past, likely scenarios of future global warming have been developed for various warming levels that might be reached during the current century. The paleoanalogue of global warming by 0.7–1°C is the Holocene climatic optimum (5.5–6 ka B.P.) and that by 1.7–2°C is the last interglacial optimum (about 125 ka B.P.). The complex analysis concerning response of the principal ecosystem components to the expected warming signifies that there will not be any shifts of vegetation zones during the 21st century; reconstruction will touch only the internal structure of vegetable associations and broadening of interzonal ecotones.     

<Emphasis Type="Italic">An Inconvenient Truth</Emphasis> and the scientists

An Inconvenient Truth provides an opportunity to examine the differences between scientific statements and the mixed statements made by politicians. The Gore movie is a powerful example of the latter. There are some inaccuracies and exaggerations in the film, but on the whole it represents mainstream scientific views on global warming. This essay looks into the state of the art of climate change research including its scientific underpinnings. Climate science is in a state of ‘normal science’ as discussed by Kuhn. There is a large body of scientists who are adherents to the paradigm and there does not appear to be any serious alternative at this time.     

An Inconvenient Truth: blurring the lines between science and science fiction

Al Gore’s movie An Inconvenient Truth gives a variety of unusually biased interpretations of the state of climate science and global warming theory. These cover a wide range of natural events and processes which could potentially be impacted by global warming, but which the movie misrepresents as clear examples of the human influence on climate. A few examples include the mixing up of cause and effect in his graphical portrayal of temperature and carbon dioxide variations over hundreds of thousands of years; the repeated depiction of ice calving from glaciers as a sign of global warming; the implication that Hurricane Katrina was the fault of humans; and the particularly extreme view that the Greenland ice sheet will melt, flooding coastal cities worldwide. Ultimately, all of these are related to the widespread perception that scientists have uniquely tied global warming to anthropogenic greenhouse gas emissions. The real inconvenient truth is that science has no idea how much of recent warming is natural versus the result of human activities.     

Comparison of element abundance between the exposed crust of the continent of China and the global averaged upper continental crust: Constraints on crustal evolution and some speculations

Based on the results of a study of regional element abundance in eastern China and the 1:200 000 geochemical surveys in northern Xinjiang, the element geochemical characteristics of the exposed crust in 23 tectonic units of the continent of China are summarized. Compared with the global average abundance of the upper continental crust, the exposed crust of the continent of China is compositionally more evolved than the upper crust of the island arc, but less evolved than the mature Precambrian Canadian shield. The exposed crust of the North China and Yangtze platforms has a lower SiO₂ content, but markedly higher CaO and MgO contents due to the presence of widespread carbonate strata, which suggests that we should not neglect the contribution of carbonate rocks in the study of the exposed crust and the element abundance of the upper crust. In comparison with two recently published average compositional models of the global upper continental crust, the exposed crust of the continent of China is depleted in Au, Hg, Mo, Sn, and W, which suggests that their abundance in the present global models is overestimated. The exposed crust of the North China platform and the Qinling-Dabieshan fold belt to its south has lower μ(²³⁸U/²⁰⁴Pb) values (<8), but other regions of the continent of China exhibit much higher μ values, which implies that the low μ feature of the North China platform and its adjacent regions does not have global significance. Considering the apparent lateral variation in composition of the exposed crust for the tectonic units of the continent of China, there is no adequate reason to take the average upper crust compositional model of the North China platform and its adjacent regions as a reliable composition representative for Chinese and global upper continental crust composition. Translated from Geological Bulletin of China, 2005, 24(10–11): 906–915 [译自: 地质通报]     

Deccan volcanism linked to the Cretaceous-Tertiary boundary mass extinction: New evidence from ONGC wells in the Krishna-Godavari Basin

A scientific challenge is to assess the role of Deccan volcanism in the Cretaceous-Tertiary boundary (KTB) mass extinction. Here we report on the stratigraphy and biologic effects of Deccan volcanism in eleven deep wells from the Krishna-Godavari (K-G) Basin, Andhra Pradesh, India. In these wells, two phases of Deccan volcanism record the world’s largest and longest lava mega-flows interbedded in marine sediments in the K-G Basin about 1500 km from the main Deccan volcanic province. The main phase-2 eruptions (∼80% of total Deccan Traps) began in C29r and ended at or near the KTB, an interval that spans planktic foraminiferal zones CF1–CF2 and most of the nannofossil Micula prinsii zone, and is correlative with the rapid global warming and subsequent cooling near the end of the Maastrichtian. The mass extinction began in phase-2 preceding the first of four mega-flows. Planktic foraminifera suffered a 50% drop in species richness. Survivors suffered another 50% drop after the first mega-flow, leaving just 7 to 8 survivor species. No recovery occurred between the next three mega-flows and the mass extinction was complete with the last phase-2 mega-flow at the KTB. The mass extinction was likely the consequence of rapid and massive volcanic CO₂ and SO₂ gas emissions, leading to high continental weathering rates, global warming, cooling, acid rains, ocean acidification and a carbon crisis in the marine environment.     

全球变暖停滞的研究进展回顾

1998—2012年,全球平均地面增温速率较之前明显趋缓,出现全球变暖停滞现象,该现象的成因与机制是当前气候变化研究的一个热点领域。主要从外部强迫和内部变率2个角度回顾全球变暖停滞产生机制的研究进展。从气候系统外部强迫影响来说,全球变暖停滞主要受到太阳活动、火山爆发、气溶胶以及平流层水汽等的影响。从气候系统内部调控作用来看,全球增温速率减缓主要受到太平洋、大西洋、印度洋和南大洋自然变率以及相应的热量再分配过程的影响。全球变暖停滞期间气候系统内部能量并没有减少,其中一部分能量被转移并储存在了海洋中深层,从而对全球增温减缓产生影响。同时,重点回顾了针对部分耦合强迫作用的"起搏器"试验,该类试验是研究全球变暖停滞的特征、成因及机制的有力手段。此外,也总结了全球变暖停滞现象对气候系统能量收支平衡、资料、模拟以及相关政策制定等方面带来的挑战,展望了未来的研究重点。     

Annual variation of temperature sensitivity of soil organic carbon decomposition in North peatlands: implications for thermal responses of carbon cycling to global warming

Temperature sensitivities of microbial respiration and dissolved organic carbon (DOC) production were investigated by using a novel method, thermal gradient (2–20°C) temperature bar, in two typical peatlands (bog and fen) in North Wales, UK over 12 months. The study indicated that temperature sensitivity of soil organic carbon decomposition in North peatlands was regulated not only by temperature but soil water content, dry–rewet event and phenologies. Potential decreases of Q₁₀ (CO₂) with increasing soil temperature were confirmed in both peatlands, but Q₁₀ (DOC) increase with increasing soil temperature in both bog and fen sites. These results imply, if other factors such as the so-called CO₂ fertilization effect are simultaneously taken into account, that the feedback of global warming induced CO₂ release from peatlands to climate change may be overestimated in current biogeochemical models. However, global warming might have been nonlinearly accelerating DOC thermal production, and therefore it helps explaining the causes of remarkable increase of DOC in surface water in the Northern Hemisphere during last several decades.     

Review of the Research Progress in Global Warming Hiatus

From 1998 to 2012, the warming rate of global mean surface air temperature showed significantly slower than before, which is referred to as the global warming hiatus. The causes and underlying mechanisms of this phenomenon are currently a hot topic of climatic change research. The research significance of global warming hiatus was discussed and relevant research progress was reviewed from two perspectives of external forcings and internal variabilities. In term of external forcings, global warming hiatus is mainly affected by solar activities, volcanic eruptions, aerosols and stratospheric water vapor. With respect to internal variabilities, the warming rate of global mean surface air temperature slowdown is mainly related to the natural variabilities of the Pacific Ocean, the Atlantic Ocean, the Indian Ocean and the Southern Ocean and influenced by the related heat redistribution processes. During the global warming hiatus period, some energy is transferred and restored in the deep ocean so as to modulate the global warming rate, rather than there is a reduction of global total energy in the climate system. In addition, the partially coupled forcing pacemaker model experiment was also reviewed. The pacemaker experiment is a powerful tool for studying the characteristics, causes and underlying mechanisms of the global warming hiatus. Besides, some challenges resulted from the global warming hiatus, including the global energy imbalance, data, simulation and related policy-making were summarized, and future research directions were also discussed.     

<Emphasis Type="Italic">An Inconvenient Truth</Emphasis>: the scientific argument

The movie An Inconvenient Truth is a powerful portrayal of global warming and its impacts. The main scientific argument presented in the movie is for the most part consistent with the weight of scientific evidence, but with some of the main points needing updating, correction, or qualification. The detailed argument relies almost entirely on past and current evidence and neglects almost all information that can be gained from computer models, perhaps because such information would be difficult for a lay audience to grasp, believe, or connect with emotionally. This places an undue weight on current events as signs of ongoing climate change: some such events are apparently not related at all to climate change, while for other specific events the role of global warming is difficult or impossible to establish.     

Some features of twisting of the Earth in geological history: the tectonophysical aspect

In this work some examples of “twisting” of the Earth in the geologic past are given: displacement of the northern parts of the global submeridional structures to the west relative to their southern parts; the rotation of the “geodynamic pair” of Siberia-Laurentia in the Proterozoic; sinistral displacement of the Northern Hemisphere relative to the Southern Hemisphere after the collapse of the last Pangaea; the equatorial rotation of the continental plates; oblique orientation of the global network of planetary fracturing; an inclination of the axis of submeridional compression; sinistral “beveling”; the dextral “twisting” of Venus. All these examples confirm the idea of possible sinistral “twisting” of the Earth that has been proposed by many authors. The cause of such “twisting” is unclear, although it is likely connected with the Earth’s rotation around its axis. Some of these examples show that many paleomagnetic reconstructions can be usefully discussed in a tectonophysical aspect. Moreover, in connection with this data, the development of a new scientific field, called “paleomagnetic tectonophysics”, is possible.     

Late Paleocene–early Eocene Tethyan carbonate platform evolution — A response to long- and short-term paleoclimatic change

The early Paleogene experienced the most pronounced long-term warming trend of the Cenozoic, superimposed by transient warming events such as the Paleocene–Eocene Thermal Maximum (PETM). The consequences of climatic perturbations and associated changes on the evolution of carbonate platforms are relatively unexplored. Today, modern carbonate platforms, especially coral reefs are highly sensitive to environmental and climatic change, which raises the question how (sub)tropical reef systems of the early Paleogene reacted to gradual and sudden global warming, eutrophication of shelf areas, enhanced CO₂ levels in an ocean with low Mg/Ca ratios. The answer to this question may help to investigate the fate of modern coral reef systems in times of global warming and rising CO₂ levels.Here we present a synthesis of Tethyan carbonate platform evolution in the early Paleogene (~ 59–55 Ma) concentrating on coral reefs and larger foraminifera, two important organism groups during this time interval. We discuss and evaluate the importance of the intrinsic and extrinsic factors leading to the dissimilar evolution of both groups during the early Paleogene. Detailed analyses of two carbonate platform areas at low (Egypt) and middle (Spain) paleolatitudes and comparison with faunal patterns of coeval platforms retrieved from the literature led to the distinction of three evolutionary stages in the late Paleocene to early Eocene Tethys: Stage I, late Paleocene coralgal-dominated platforms at low to middle paleolatitudes; stage II, a transitional latest Paleocene platform stage with coralgal reefs dominating at middle paleolatitudes and larger foraminifera-dominated (Miscellanea, Ranikothalia, Assilina) platforms at low paleolatitudes; and stage III, early Eocene larger foraminifera-dominated (Alveolina, Orbitolites, Nummulites) platforms at low to middle paleolatitudes. The onset of the latter prominent larger foraminifera-dominated platform correlates with the Paleocene/Eocene Thermal Maximum.The causes for the change from coral-dominated platforms to larger foraminifera-dominated platforms are multilayered. The decline of coralgal reefs in low latitudes during platform stage II is related to overall warming, leading to sea-surface temperatures in the tropics beyond the maximum temperature range of corals. The overall low occurrence of coral reefs in the Paleogene might be related to the presence of a calcite sea. At the same time larger foraminifera started to flourish after their near extinction at the Cretaceous/Paleogene boundary. The demise of coralgal reefs at all studied paleolatitudes in platform stage III can be founded on the effects of the PETM, resulting in short-term warming, eutrophic conditions on the shelves and acidification of the oceans, hampering the growth of aragonitic corals, while calcitic larger foraminifera flourished. In the absence of other successful carbonate-producing organisms, larger foraminifera were able to take over the role as the dominant carbonate platform inhabitant, leading to a stepwise Tethyan platform stage evolution around the Paleocene/Eocene boundary. This szenario might be also effective for threatened coral reef sites.     

Constraints on graphite crystallinity in some Spanish fluid-deposited occurrences from different geologic settings

Epigenetic, vein-type graphite mineralization originates by deposition from C—O—H fluids in high-temperature environments. Consequently, fluid-deposited graphite is uniformly highly crystalline in volumetrically large occurrences. This work examines the factors controlling graphite crystallinity in fluid-deposited occurrences with reference to some case studies from southern Spain where vein-type graphite is associated with a variety of host rocks. Possible causes influencing high crystallinity of graphite in these occurrences include: (1) large graphite occurrences are generated from large volumes of fluids that maintain their temperatures for long periods of time, which is easier at higher temperatures; (2) high temperature conditions are required for a fluid to precipitate a major part of its dissolved carbon during a small temperature decrease; (3) carbon is incorporated into C—O—H fluids mainly through devolatilization reactions which also require high temperatures; (4) highly crystalline graphite generated at high-T/high-P conditions is less susceptible to resorption as P decreases or by subsequent fluid flow; (5) graphite precipitation involves high activation energy that can be overcome only if the temperature is high enough. These causes can be extrapolated to most vein-type graphite deposits worldwide. Received: 23 February 1998 / Accepted: 28 April 1998     

A contrasting study of freezing disasters in January 2008 and in winter of 1954/1955 in China

The present paper has made a comparison of major similarities and differences of extreme cold events between the cold and warm periods for recent 50 years, in order to gain a better insight into the impact of the global warming on extreme cold events in China. Two typical events of low temperature, ice freezing and snow disasters that occurred in January 2008 and in the winter of 1954/1955, respectively, are selected as representative cases for the cold period (1950’s–1970’s) and the warm period (1980’s-present). The contrasting study has revealed that these two events both occurred under long-persistent blocking circulation over Eurasian continent, with continuous invasions of strong cold air into China mainland. They nearly brought about similar weather disasters such as extensive low temperature, record-breaking freezing rains and exceptionally heavy snowfalls. However, due to active northward transport of warm and moist air from Bay of Bengal and Indo-China Peninsula in the warm period, the January 2008 case had longer freezing rain days and heavier snowstorms in South China, thus leading to much more severe damage to electric grids and transportations. The case of the 1954/1955 winter was a stronger, extreme cold event than the case of January 2008, in terms of magnitudes of temperature drop and severity of impact on river icing. It was gradually recovered to normal condition while the case of January 2008 had a very rapid recovery to warming condition due to impact of the global warming.     

Probable consequences of climate change on freshwater production of Adams River sockeye salmon (Oncorynchus nerka)

We combine information on the influence of temperature on the thermal physiology, growth, and survival of sockeye salmon (Oncorhynchus nerka) with projections of temperature change associated with a doubling of atmospheric CO₂ concentrations (over pre-industrial levels) to determine the effect of global warming on two freshwater life history stages (lake residence of juveniles, and spawning by adults) of sockeye salmon from Adams River, British Columbia. Air temperatures are expected to increase by approximately 4.0° and 2.5° C in the summer and winter respectively in the vicinity of the Adams River. Shuswap Lake is used as a rearing area by the juvenile sockeye salmon and global warming will probably change the production characteristics of lake towards a more oligotrophic system. This will cause a reduction in the abundance and availability of food for the juvenile sockeye salmon, and hence a decrease in their freshwater growth, and freshwater and marine survival. However, the increased temperature encountered by adults on the spawning grounds of the Adams River is unlikely to result in higher rates of prespawning mortality. It is anticipated that the net effect of global warming over all freshwater life history stages will be a reduction in the freshwater production of Adams River sockeye salmon.     

Some scientific problems facing research on hydrological processes in an inland river basin

The challenge is put forward to scientific hydrology by the advancement of water sciences; that is, how should we carry out a multidisciplinary, integrated and cooperative research on hydrological processes in the basin, regional and global scales, in order to better understand the role water plays in the changes of the natural resources and environment of the earth, and to understand the hydrosphere and its interactions with the atmosphere, lithosphere and biosphere. How the changes and transformation of the components of the water cycle and water balance occur in an inland river basin has yet to be understood. We also need to understand what the interactions of water cycle, ecosystems and environment are, and what the responses and feedback of the changes to global change and to human activities are. The water cycle in an inland river basin characterizes the runoff generation region of the mountains upstream, the artificial oases region of water resources exploitation and utilization midstream and the natural desert oases region of runoff dissipating downstream. The mountain hydrological processes are discussed from water cycle, energy balance, water balance and ecological processes. The interactions of water and vegetation are discussed in relation to ecohydrology, and the hydrological processes in the ground water-soil-vegetation layer are discussed from the concept of the critical zone newly put forward abroad. The basic frame is put forward to carry out the field measurement, experiment and studies of hydrological processes in a typical inland river basin. __________ Translated from Advances in Earth Science, 2007, 22(9): 940–953 [译自: 地球科学进展]     

Analysis of extreme low-temperature events during the warm season in Northeast China

The trends of global warming are increasingly significant, especially in the middle and high latitude regions of the northern hemisphere, where the impact of climate change on extreme events is becoming more noticeable. Northeast China is located in a high latitude region and is sensitive to climate change. Extreme minimum temperatures causing cold damage during the warm season is a major type of agro-meteorological disaster in Northeast China, which causes serious reductions in crop yield. In this paper, we analyzed the temporal and spatial trends in the frequency of extreme minimum temperatures during the warm season (from May to September) during 1956–2005 in Northeast China. Abrupt climatic changes were identified using the Mann–Kendall test. The results show that the frequency of extreme minimum temperature days during the warm season in Northeast China decreases significantly from 1956 to 2005 with a background of climate warming. The highest number of extreme minimum temperature days occurred in the 1970s and 1980s, and there was an abrupt climatic change in 1993. The spatial analysis identified that the north and southeast of the region experienced a larger decrease in the number of extreme low temperature days than the west and south of the region. Rice, sorghum, corn, and soybeans are most vulnerable to cold damage. In severe low temperature years, the average crop yield was reduced by 15.2% in Northeast China.     

Impact of global warming on cyclonic disturbances over south Asian region

A state-of-the-art regional climate modelling system, known as PRECIS (Providing REgional Climates for Impacts Studies) developed by the Hadley Centre for Climate Prediction and Research, UK is applied over the Indian domain to investigate the impact of global warming on the cyclonic disturbances such as depressions and storms. The PRECIS simulations at 50 × 50 km horizontal resolution are made for two time slices, present (1961–1990) and the future (2071–2100), for two socioeconomic scenarios A2 and B2. The model simulations under the scenarios of increasing greenhouse gas concentrations and sulphate aerosols are analysed to study the likely changes in the frequency, intensity and the tracks of cyclonic disturbances forming over north Indian Ocean (Bay of Bengal and Arabian Sea) and the Indian landmass during monsoon season. The model overestimates the frequency of cyclonic disturbances over the Indian subcontinent in baseline simulations (1961–1990). The change is evaluated towards the end of present century (2071–2100) with respect to the baseline climate. The present study indicates that the storm tracks simulated by the model are southwards as compared to the observed tracks during the monsoon season, especially for the two main monsoon months, viz., July and August. The analysis suggests that the frequency of cyclonic disturbances forming over north Indian Ocean is likely to reduce by 9% towards the end of the present century in response to the global warming. However, the intensity of cyclonic disturbances is likely to increase by about 11% compared to the present.     

Driving forces responsible for aeolian desertification in the source region of the Yangtze River from 1975 to 2005

The Yangtze River is the China’s longest river and the third-longest river in the world. The river’s source region in the Qinghai-Tibet Plateau is especially sensitive to global environmental change because of its high elevation and cold environment. Under the influence of global warming, aeolian desertified land has expanded rapidly in this area. To assess the trends in aeolian desertification from 1975 to 2005, remote-sensing and GIS technology were used to monitor the extent of aeolian desertification in 1975, 1990, 2000, and 2005. The data sources included Landsat multi-spectral scanner images acquired in 1975, Enhanced Thematic Mapper (ETM+) images acquired in 2000, and Thematic Mapper (TM) images acquired in 1990 and 2005. Images recorded between June and October were selected, when vegetation grew well, because aeolian desertified land was more easily recognized during this period. Thematic maps, including land use and geomorphologic maps, were used as supplementary data. Aeolian desertification maps (1:100000) were produced for each year from the Landsat images through visual interpretation. The area of aeolian desertified land increased by 2,678.43 km² from 1975 to 2005, accounting for 8.8% of the total area of aeolian desertified land in 1975, an increase of 89.28 km² a⁻¹. Increasing mean annual temperature and the combination of a dry, cold, and windy climate in winter and spring were mainly responsible for the expansion of desertified land.     

Research on the Global Warming Hiatus

A global warming “hiatus” has been observed since the beginning of the 21st century despite the increase in heat-trapping greenhouse gases, challenging the current global warming studies. Focusing on the phenomena and mechanisms of the global warming “hiatus”, the National Key Research Program of China launched a project in July, 2016. The main research themes of this project cover: ①Revealing the spatial and temporal variability of the global warming hiatus, and quantifying the contributions of external forcing and internal (natural) variability, respectively; ②Revealing the role of the atmosphere in the global heat and energy redistribution under global warming hiatus; ③Revealing the role of the ocean in the global heat and energy redistribution under global warming hiatus; ④Investigating the predictability of the global warming hiatus. The key scientific issues to be resolved include: ①Identifying characteristics of the global warming hiatus and discerning the roles of decadal, multi-decadal oscillations; ②Revealing the role of ocean-atmosphere dynamical processes in the global redistribution of heat and energy; ③Understanding the predictability of the global warming hiatus. The research aims to predict the future development of the global warming hiatus, and to point out the possible impacts on China and other important areas, including “The Belt and Road” core area and the Polar Regions.     

藏东南嘎龙曲冰川泥石流的物源特征及其对扎墨公路的影响

在全球气候变暖的大背景下,冰川消融加剧,冰舌后退,冰川泥石流加剧。扎墨公路是目前通往西藏墨脱的唯一公路,公路必经的嘎龙曲发育藏东南地区典型的海洋性冰川泥石流,针对嘎龙曲冰川泥石流的物源特征,经现场调查得出,嘎龙曲冰川泥石流物源类型有冰碛物物源、崩塌型物源以及沟道堆积型物源三类,总结分析了三种物源类型的分布特征和启动模式。通过建立物源计算模型,定量计算嘎龙曲沟域内可参与泥石流活动的松散固体物源动储量为366.28×104 m3,其中冰碛物物源为主要的动储量物源,物源补给特征在藏东南海洋性冰川发育区域具有一定代表性。嘎龙曲沟域内水动力分布的不均一特性决定了物源启动参与泥石流活动的不均一性,随着全球气候变暖影响下水动力条件的增强,嘎龙曲冰川泥石流对扎墨公路的危害会愈加严重。