Carbon dioxide emissions from Deccan volcanism and a K/T boundary greenhouse effect

A greenhouse warming caused by increased emissions of carbon dioxide from the Deccan Traps volcanism has been suggested as the cause of the terminal Cretaceous extinctions on land and in the sea. We estimate total eruptive and noneruptive CO2 output by the Deccan eruptions (from 6 to 20 x 10(16) moles) over a period of several hundred thousand years based on best estimates of the CO2 weight fraction of the original basalts and basaltic melts, the fraction of CO2 degassed, and the volume of the Deccan Traps eruptions. Results of a model designed to estimate the effects of increased CO2 on climate and ocean chemistry suggest that increases in atmospheric pCO2 due to Deccan Traps CO2 emissions would have been less than 75 ppm, leading to a predicted global warming of less than 1 degree C over several hundred thousand years. We conclude that the direct climate effects of CO2 emissions from the Deccan eruptions would have been too weak to be an important factor in the end-Cretaceous mass extinctions.     

Climate change and global cycling of persistent organic pollutants: A critical review

Climate warming, one of the main features of global change, has exerted indelible impacts on the environment, among which the impact on the transport and fate of pollutants has aroused widespread concern. Persistent organic pollutants (POPs) are a class of pollutants that are transported worldwide. Determining the impact of climate warming on the global cycling of POPs is important for understanding POP cycling processes and formulating relevant environmental policies. In this review, the main research findings in this field over the past ten years are summarized and the effects of climate warming on emissions, transport, storage, degradation and toxicity of POPs are reviewed. This review also summarizes the primary POP fate models and their application. Additionally, research gaps and future research directions are identified and suggested. Under the influence of climate change, global cycling of POPs mainly shows the following responses. (1) Global warming directly promotes the secondary emission of POPs; for example, temperature rise will cause POPs to be re-released from soils and oceans, and melting glaciers and permafrost can re-release POPs into freshwater ecosystems. (2) Global extreme weather events, such as droughts and floods, result in the redistribution of POPs through intense soil erosion. (3) The changes in atmospheric circulation and ocean currents have significantly influenced the global transport of POPs. (4) Climate warming has altered marine biological productivity, which has changed the POP storage capacity of the ocean. (5) Aquatic and terrestrial food-chain structures have undergone significant changes, which could lead to amplification of POP toxicity in ecosystems. (6) Overall, warming accelerates the POP volatilization process and increases the amount of POPs in the environment, although global warming facilitates their degradation at the same time. (7) Various models have predicted the future environmental behaviors of POPs. These models are used to assist governments in comprehensively considering the impact of global warming on the environmental fate of POPs and therefore controlling POPs effectively. Future studies should focus on the synergistic effects of global changes on the cycling of POPs. Additionally, the interactions among global carbon cycling, water cycling and POP cycling will be a new research direction for better understanding the adaptation of ecosystems to climate change.     

Control of atmospheric CO<Subscript>2</Subscript> concentrations by 2050: A calculation on the emission rights of different countries

This paper is to provide quantitative data on some critical issues in anticipation of the forthcoming international negotiations in Denmark on the control of atmospheric CO2 concentrations. Instead of letting only a small number of countries dominate a few controversial dialogues about emissions reductions, a comprehensive global system must be established based on emissions allowances for different countries, to realize the long-term goal of controlling global atmospheric CO2 concentrations. That a system ...     

Fugitive emissions from Norwegian oil and gas production

Fugitive hydrocarbon emissions from oil and gas production, always a safety concern, are currently a growing environmental and economic concern. Fugitive emissions from the offshore industry comprise mainly methane, which has an atmospheric warming contribution of approximately 14 times that of CO₂, and Volatile Organic Compounds (VOCs), which have an atmospheric warming contribution of around twice that of CO₂.

Current studies indicate that fugitive emissions are approximately equivalent to 0.02% of the total gas produced in 1992 on the Norwegian Continental Shelf. A positive downward trend in fugitive emissions from oil and gas production has been identified and attributed to advances in technology and changes in design and operating philosophy.     

The role of atmospheric nuclear explosions on the stagnation of global warming in the mid 20th century

This study suggests that the cause of the stagnation in global warming in the mid 20th century was the atmospheric nuclear explosions detonated between 1945 and 1980. The estimated GST drop due to fine dust from the actual atmospheric nuclear explosions based on the published simulation results by other researchers (a single column model and Atmosphere-Ocean General Circulation Model) has served to explain the stagnation in global warming. Atmospheric nuclear explosions can be regarded as full-scale in situ tests for nuclear winter. The non-negligible amount of GST drop from the actual atmospheric explosions suggests that nuclear winter is not just a theory but has actually occurred, albeit on a small scale. The accuracy of the simulations of GST by IPCC would also be improved significantly by introducing the influence of fine dust from the actual atmospheric nuclear explosions into their climate models; thus, global warming behavior could be more accurately predicted.     

The inhibition of marine nitrification by ocean disposal of carbon dioxide

In an attempt to reduce the threat of global warming, it has been proposed that the rise of atmospheric carbon dioxide concentrations be reduced by the ocean disposal of CO2 from the flue gases of fossil fuel-fired power plants. The release of large amounts of CO2 into mid or deep ocean waters will result in large plumes of acidified seawater with pH values ranging from 6 to 8. In an effort to determine whether these CO2-induced pH changes have any effect on marine nitrification processes, surficial (euphotic zone) and deep (aphotic zone) seawater samples were sparged with CO2 for varying time durations to achieve a specified pH reduction, and the rate of microbial ammonia oxidation was measured spectrophotometrically as a function of pH using an inhibitor technique. For both seawater samples taken from either the euphotic or aphotic zone, the nitrification rates dropped drastically with decreasing pH. Relative to nitrification rates in the original seawater at pH 8, nitrification rates were reduced by ca. 50% at pH 7 and more than 90% at pH 6.5. Nitrification was essentially completely inhibited at pH 6. These findings suggest that the disposal of CO2 into mid or deep oceans will most likely result in a drastic reduction of ammonia oxidation rates within the pH plume and the concomitant accumulation of ammonia instead of nitrate. It is unlikely that ammonia will reach the high concentration levels at which marine aquatic organisms are known to be negatively affected. However, if the ammonia-rich seawater from inside the pH plume is upwelled into the euphotic zone, it is likely that changes in phytoplankton abundance and community structure will occur. Finally, the large-scale inhibition of nitrification and the subsequent reduction of nitrite and nitrate concentrations could also result in a decrease of denitrification rates which, in turn, could lead to the buildup of nitrogen and unpredictable eutrophication phenomena. Clearly, more research on the environmental effects of ocean disposal of CO2 is needed to determine whether the potential costs related to marine ecosystem disturbance and disruption can be justified in terms of the perceived benefits that may be achieved by temporarily delaying global warming.     

Numerical analysis of the source-sink alternation of composite global warming potential of the paddy ecosystem in the Yangtze Delta

The three important greenhouse gases, namely CO2, CH4 and N2O[1,2], participate in the process of carbon and nitrogen cycling in the paddy field simultaneously. CO2 is assimilated by rice through photosynthesis, which means the paddy field is the sink of …     

The Global Warming Debate: A Review of the State of Science

A review of the present status of the global warming science is presented in this paper. The term global warming is now popularly used to refer to the recent reported increase in the mean surface temperature of the earth; this increase being attributed to increasing human activity and in particular to the increased concentration of greenhouse gases (carbon dioxide, methane and nitrous oxide) in the atmosphere. Since the mid to late 1980s there has been an intense and often emotional debate on this topic. The various climate change reports (1996, 2001) prepared by the IPCC (Intergovernmental Panel on Climate Change), have provided the scientific framework that ultimately led to the Kyoto protocol on the reduction of greenhouse gas emissions (particularly carbon dioxide) due to the burning of fossil fuels. Numerous peer-reviewed studies reported in recent literature have attempted to verify several of the projections on climate change that have been detailed by the IPCC reports.The global warming debate as presented by the media usually focuses on the increasing mean temperature of the earth, associated extreme weather events and future climate projections of increasing frequency of extreme weather events worldwide. In reality, the climate change issue is considerably more complex than an increase in the earth’s mean temperature and in extreme weather events. Several recent studies have questioned many of the projections of climate change made by the IPCC reports and at present there is an emerging dissenting view of the global warming science which is at odds with the IPCC view of the cause and consequence of global warming. Our review suggests that the dissenting view offered by the skeptics or opponents of global warming appears substantially more credible than the supporting view put forth by the proponents of global warming. Further, the projections of future climate change over the next fifty to one hundred years is based on insufficiently verified climate models and are therefore not considered reliable at this point in time.     

Siberian gas venting and the end-Permian environmental crisis

The end of the Permian period is marked by global warming and the biggest known mass extinction on Earth. The crisis is commonly attributed to the formation of the Siberian Traps Large Igneous Province although the causal mechanisms remain disputed. We show that heating of Tunguska Basin sediments by the ascending magma played a key role in triggering the crisis. Our conclusions are based on extensive field work in Siberia in 2004 and 2006. Heating of organic-rich shale and petroleum bearing evaporites around sill intrusions led to greenhouse gas and halocarbon generation in sufficient volumes to cause global warming and atmospheric ozone depletion. Basin scale gas production potential estimates show that metamorphism of organic matter and petroleum could have generated > 100,000 Gt CO₂. The gases were released to the end-Permian atmosphere partly through spectacular pipe structures with kilometre-sized craters. Dating of a sill intrusion by the U–Pb method shows that the gas release occurred at 252.0 ± 0.4 million years ago, overlapping in time with the end-Permian global warming and mass extinction. Heating experiments to 275 °C on petroleum-bearing rock salt from Siberia suggests that methyl chloride and methyl bromide were significant components of the erupted gases. The results indicate that global warming and ozone depletion were the two main drivers for the end-Permian environmental crisis. We demonstrate that the composition of the heated sedimentary rocks below the flood basalts is the most important factor in controlling whether a Large Igneous Provinces causes an environmental crisis or not. We propose that a similar mechanism could have been responsible for the Triassic-Jurassic (~ 200 Ma) global warming and mass extinction, based on the presence of thick sill intrusions in the evaporite deposits of the Amazon Basin in Brazil.     

20世纪温度变化中自然变率和人为因素的影响:基于耦合气候模式的归因模拟

本文基于中国科学院大气物理研究所大气科学和地球流体力学国家重点实验室(LASG/IAP)发展的气候系统模式FGOALS_gl对近百年气温变化的模拟,讨论了自然变率和人为因素对20世纪全球变暖的相对贡献.数值试验结果表明,在自然和人为因子的共同强迫作用下,耦合模式能够合理再现20世纪全球平均气温随时间的演变;仅在自然因子作用下,模式不能再现1970年以后的全球变暖.自然因素对20世纪第一次变暖的作用是显著的,但温室气体是20世纪后期变暖的主要原因.在这一定性结论基础上,进一步对近百年变化中自然和人为因素的相对贡献做定量的归因分析,结果表明,除赤道中东太平洋和北大西洋外,人为因素对近百年的增暖起决定性作用.对全球、半球及大陆尺度而言,外强迫可以解释平均气温变化的70%以上,而内部变率贡献较小;但对于区域尺度而言,多数地区内部变率的贡献大于外强迫,区域尺度气温变化的机制较全球、半球尺度要复杂.对中国地区而言,20世纪早期的气温变化受自然变率影响,但20世纪后期的变暖主要是温室气体增加的结果.中国东部气温变化的空间分布表明,自然因素对近50年及近百年中国地区的变暖趋势贡献较小.在自然和人为因子共同作用下,模式能够再现近50年中国东部气温变化冬春两季增暖的特征、但没有模拟出夏季长江中下游地区及淮河流域的降温趋势;自然因子试验的结果表明,太阳活动对该区域的变冷有贡献,但模式无法再现该地区气温的季节变化特征.     

Climate change during the last 150 million years: reconstruction from a carbon cycle model

Variations of the atmospheric CO₂ level and the global mean surface temperature during the last 150 Ma are reconstructed by using a carbon cycle model with high-resolution input data. In this model, the organic carbon budget and the CO₂ degassing from the mantle, both of which would characterize the carbon cycle during the Cretaceous, are considered, and the silicate weathering process is formulated consistently with an abrupt increase in the marine strontium isotope record for the last 40 Ma. The second-order variations of the atmospheric CO₂ level and the global mean surface temperature in addition to the first-order cooling trend are obtained by using high-resolution data of carbon isotopic composition of marine limestone, seafloor spreading rate, and production rate of oceanic plateau basalt. The results obtained from this model are in good agreement with the previous estimates of palaeo-CO₂ level and palaeoclimate inferred from geological, biogeochemical, and palaeontological models and records. The system analyses of the carbon cycle model to understand the cause of the climate change show that the dominant controlling factors for the first-order cooling trend of climate change during the last 150 Ma are tectonic forcing such as decrease in volcanic activity and the formation and uplift of the Himalayas and the Tibetan Plateau, and, to a lesser extent, biological forcing such as the increase in the soil biological activity. The mid-Cretaceous was very warm because of the high CO₂ level (4–5 PAL) maintained by the enhanced CO₂ degassing rate due to the increased mantle plume activities and seafloor spreading rates at that time, although the enhanced organic carbon burial would have a tendency to decrease the CO₂ level effectively at that period. The variation of organic carbon burial rate may have been responsible for the second-order climate change during the last 150 Ma.     

Effect of experimental and seasonal warming on litter decomposition in a temperate stream

Litter decomposition, a fundamental ecosystem process in woodland streams, is potentially affected by the predicted increase in water temperature. Here, we assessed the effects of experimental and seasonal warming on oak litter decomposition and on the relative contributions of microbes and invertebrates to this process. Experimental warming (~3 °C) stimulated litter decomposition in the coldest, but not in the warmest, months. This may be attributed to (1) higher temperature sensitivity of decomposition at lower ambient temperature due to temperature limitation of enzymatic activity, (2) higher relative temperature increase in winter than in warmer months, (3) existence of a previous warming period in winter, and (4) stronger stimulation of the activity of detritivores by warming in winter due to the prevalence of earlier (smaller) instars than in warmer months. The low response of litter decomposition to warming may have been due to the low nutrient availability in the study stream. The 30-day litter decomposition was stimulated over the seasonal gradient (monthly mean temperature: 6–16 °C), which may be attributed to a stimulation of metabolic activities by warming and to changes in detritivore life history over the seasons. The stimulation of litter decomposition with temperature suggests that the rate of CO₂ release from freshwaters will increase under global warming. However, invertebrate-driven litter decomposition was more responsive to warming than microbial-driven litter decomposition, suggesting that a larger fraction of litter carbon may be converted into secondary production and stored in the system for longer periods.     

Comments on “Evidence for global runoff increase related to climate warming” by Labat et al.

We have examined the evidence presented by Labat et al. and found that (1) their claims for a 4% increase in global runoff arising from a 1 °C increase in air temperature and (2) that their article provides the “first experimental data-based evidence demonstrating the link between the global warming and the intensification of the global hydrological cycle” are not supported by the data presented. Our conclusions are based on the facts that (1) their discharge records exhibit non-climatic influences and trends, (2) their work cannot refute previous studies finding no relation between air temperature and runoff, (3) their conclusions cannot explain relations before 1925, and (4) the statistical significance of their results hinges on a single data point that exerts undue influence on the slope of the regression line. We argue that Labat et al. have not provided sufficient evidence to support their claim for having detected increases in global runoff resulting from climate warming.     

Ice sheets and the CO2 problem

In this review, the carbon dioxide problem is discussed, with special reference to the possible effects of a global warming on the ice sheets of Greenland and Antarctica. Instead of detailed projections of future climate and the consequences, the basic mechanisms are explained and illustrated with results described in the literature.It is concluded that a doubling of the atmospheric CO₂ content (most likely to occur somewhere in the second half of the next century) will result in a globally-averaged warming of 2–4°C, and an intensification of the hydrological cycle. In the polar regions, this warming will be a few degrees larger and as a consequence the Greenland Ice Sheet will decrease in size. Antarctica, on the other hand, is expected to grow because of the increased snowfall. The instability of the West Antarctic Ice Sheet is also discussed and, although no conclusive prediction to its long-term response can be made, it is argued that on a short time scale (less than about 100 y) nothing dramatically wil happen to this part of Antarctica.     

GPS大气掩星技术在全球气候变化研究中的应用

人类活动引起全球变暖,衡量全球气候变化的指标有陆地、大气和海洋温度,水汽含量等等.研究对流层底层大气温度和水汽含量变化的传统方法是用数值天气预报模型和微波声纳,尚未实现用全球均匀覆盖的数据来做精确的定量研究.和GNSS系列卫星计划比较,最近发射的COSMIC卫星气象探测数据的空间、时间以及垂直分辨率都大大提高.采用COSMIC数据可以改进和量化南极洲的大气压力模型,并综合GNSS系列卫星测量的水汽和温度剖面研究全球气候变化.用一维协方差算法估计南极洲及附近海洋的大气压、温度和湿度剖面.把COSMIC卫星密集测量期间演算得到的大气折射率和GNSS系列卫星的结果进行比较.再和独立测量数据进行比较,包括南极洲自动气象观测站资料,数值天气预报模型资料,多种测高卫星水汽资料和海洋表面温度资料以及区域GPS水汽图.上述工作将改进发展中的气象遥感技术并应用于天气预报和空间天气预报及全球气候变化研究.     

Quantifying the carbon source of pedogenic calcite veins in weathered limestone: implications for the terrestrial carbon cycle

The continent is the second largest carbon sink on Earth’s surface.With the diversification of vascular land plants in the late Paleozoic,terrestrial organic carbon burial is represented by massive coal formation,while the development of soil profiles would account for both organic and inorganic carbon burial.As compared with soil organic carbon,inorganic carbon burial,collectively known as the soil carbonate,would have a greater impact on the long-term carbon cycle.Soil carbonate would have multiple carbon sources,including dissolution of host calcareous rocks,dissolved inorganic carbon from freshwater,and oxidation of organic matter,but the host calcareous rock dissolution would not cause atmospheric CO2drawdown.Thus,to evaluate the potential effect of soil carbonate formation on the atmospheric p CO2level,different carbon sources of soil carbonate should be quantitatively differentiated.In this study,we analyzed the carbon and magnesium isotopes of pedogenic calcite veins developed in a heavily weathered outcrop,consisting of limestone of the early Paleogene Guanzhuang Group in North China.Based on the C and Mg isotope data,we developed a numerical model to quantify the carbon source of calcite veins.The modeling results indicate that4–37 wt%of carbon in these calcite veins was derived from atmospheric CO2.The low contribution from atmospheric CO2might be attributed to the host limestone that might have diluted the atmospheric CO2sink.Nevertheless,taking this value into consideration,it is estimated that soil carbonate formation would lower 1 ppm atmospheric CO2within 2000 years,i.e.,soil carbonate alone would sequester all atmospheric CO2within 1 million years.Finally,our study suggests the C–Mg isotope system might be a better tool in quantifying the carbon source of soil carbonate.     

Response of macroinvertebrate communities to thermal regime in small Mediterranean streams (southern South America): Implications of global warming

The seasonal nature of the stream thermal regime has been recognized as an important factor for the structure of benthic macroinvertebrate communities. In this study, we show the importance of temperature and the potential implications of global warming on the composition of benthic macroinvertebrate communities in Andean watersheds. Here we show that thermal factors (mean temperature and monthly range) partially explain the seasonal variability of macroinvertebrates in Andean streams. Different thermal requirements were observed for macroinvertebrate families. Optimal monthly mean temperatures estimated for Gripopterygidae (Plecoptera), Hydrobiidae (Gastropoda) and Helicophidae (Trichoptera) were lower than 7 °C, while temperatures for Ameletopsidae, Baetidae (Ephemeroptera), Ecnomidae, Limnephilidae, Hydropsychidae, Leptoceridae (Trichoptera), Elmidae (Coleoptera) and Notonemouridae (Plecoptera) were close to 9.5 °C.According to our estimations, future global warming could cause important changes in the macroinvertebrate composition of Andean watersheds. Gripopterygidae, Austroperlidae, Diamphipnoidae (Plecoptera), Hydrobiidae and Helicophidae (Trichoptera) would be the most vulnerable families under the 2090 temperature predictions due to their preference for low temperature.     

Response of the equatorial Pacific thermocline to climate warming

Climate models project a significant shoaling of the thermocline over the western equatorial Pacific Ocean under global warming, which has been generally regarded as a direct response to surface wind change. This study investigates the formation processes for the equatorial Pacific thermocline response to CO₂ quadrupling using the Community Earth System Model version 1 (CESM1). In particular, an overriding method is applied to isolate and quantify the wind stress effect and the direct radiative effect of CO₂ emissions. Results show that both effects of the wind stress and direct radiative forcing are equally important for shoaling the equatorial thermocline, with the former responsible for its upper portion change and the latter for its lower portion change. Further passive tracer experiments with the ocean component of the CESM1 verify the role of ocean surface warming in shoaling the equatorial thermocline and identify the ocean circulation change in response to the surface warming as its dynamic cause of formation.     

Trends in the average temperature in Finland, 1847–2013

The change in the mean temperature in Finland is investigated with a dynamic linear model in order to define the sign and the magnitude of the trend in the temperature time series within the last 166 years. The data consists of gridded monthly mean temperatures. The grid has a 10 km spatial resolution, and it was created by interpolating a homogenized temperature series measured at Finnish weather stations. Seasonal variation in the temperature and the autocorrelation structure of the time series were taken account in the model. Finnish temperature time series exhibits a statistically significant trend, which is consistent with human-induced global warming. The mean temperature has risen very likely over 2 °C in the years 1847–2013, which amounts to 0.14 °C/decade. The warming after the late 1960s has been more rapid than ever before. The increase in the temperature has been highest in November, December and January. Also spring months (March, April, May) have warmed more than the annual average, but the change in summer months has been less evident. The detected warming exceeds the global trend clearly, which matches the postulation that the warming is stronger at higher latitudes.     

全球纬向平均大气环流基本模态年代际变化的凝聚小波分析

应用1871-2008年NCEP／NCAR月平均再分析资料,研究了1948-2008年期间全球纬向平均大气环流基本模态的年代际变化.小波凝聚谱的结果表明全球纬向平均大气环流基本模态存在显著的20年左右周期的年代际变化.小波凝聚位相的结果清楚地显示了纬向平均大气环流基本模态的变化顺序.在20年左右的年代际变化时间尺度上,全球纬向平均温度超前纬向平均位势高度2个月,同时超前纬向平均流10个月出现变化;全球纬向平均位势高度又超前纬向平均流8个月出现变化.全球温度上升(下降), 将使高纬度的纬向平均位势高度降低(升高),中低纬度的纬向平均位势高度升高(降低);进而使得中高纬和热带的纬向平均西风加(减)速或东风减(加)速,同时使极地和副热带的西风减(加)速或东风加(减)速.20世纪70年代末期以来全球显著增暖的异常信号最早出现在南半球对流层顶附近,其次出现在南半球对流层低层、北半球对流层顶附近和北半球对流层低层.