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自地球形成至寒武纪将近40亿年（距今46亿～5.4亿年,通常称为前寒武纪）的气候演变是一个具有特殊难度和挑战性的研究领域,同时也是基础和前沿的研究领域。文章选择了前寒武纪气候演化中的三个重要科学问题进行综述：大气演化、两次全球性的冰川期以及暗弱太阳问题。关于大气演化,本文首先描述了大气成分的演化历史,然后简述了影响大气成分演化的三个基本过程：大气逃逸、两次大气氧含量突然增加、碳酸盐-硅酸盐循环及其对气候系统的负反馈作用。两次全球性的冰川期分别发生在古元古代（距今24亿～21亿年）和新元古代（距今8亿～5.8亿年）,文章简述了其成因以及相关的气候模拟结果。暗弱太阳问题是地球历史气候演化的一个经典问题,论文简要地综述了一些最新的研究成果和观点。 相似文献
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我所在学校的规模不算大 ,但“麻雀虽小 ,五脏俱全” ,我这个当头头的教学、纪律、思想政治工作都得管。学校离家又远 ,我只好每天早来晚走 ,双休日也闲不着。为此 ,工作也很忙的夫人对我颇有意见 ,说我把家当成“旅店” ,什么活都不干……我脾气也不好 ,缺乏耐心 ,因此 ,家庭“战争”便时有发生。可是万万没想到 ,扭转我们家庭这种局面的竟是一条可爱的小狗———雪球。雪球真正让我们家人喜欢的不是别的 ,它会“劝架”。雪球落户我家以后 ,头两次我们家有些琐事争吵 ,它还漠然处之。有一次我真的动了气 ,争吵中不敢拿“人”怎么样 ,就把怀… 相似文献
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北京大学地球物理系数值预报班!工农兵学员 《气象》1975,1(3):1-2
在批林批孔运动继续普及、深入、持久发展的大好形势下,北京大学地球物理系气象专业数值预报班的工农兵学员,运用辩证唯物主义和历史唯物主义的观点,遵循“古为今用”的原则,研究法家著作,对古代唯物主义哲学家王充的著作——《论衡》中有关气象部份的篇章作了评注。本刊将陆续选登,供广大读者参阅。 相似文献
5.
英国利物浦大学一组地质学家,古生物学家和古气候学家研究了气候灾变对地球生物圈的影响。他们详细考察了4.39亿年以前发生的全球冰川作用过程,清楚地查明了各种生物大量灭绝的三个阶段。首先死亡的是温带的三叶虫、棘皮动物门和浮游生物;随后死亡的是热带浅海中的生物;最后轮到的是栖息在海洋大陆架中的腕足动物、珊瑚虫和苔藓动物。这样的死亡顺序决非偶然。在第一个阶段,冰川从温带气候区迅速缩小或完全消失。第二个毁灭性阶段又由于发生冰 相似文献
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地球系统科学、全球变化与可持续发展 总被引：4，自引：0，他引：4
针对当今全球性环境危机问题,阐述了地球系统科学、全球变化与可持续发展的关系,提出只有积极地进行全球变化研究,才能很好地协调自然与社会的持续稳定发展。 相似文献
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大气本底污染监测中的几个问题介绍 总被引：3，自引：1，他引：3
“大气本底污染监测”是指为了获取全球性和区域性大气组成本底浓度值的监测工作及与此相联系的各项科学研究活动。由于近半个世纪以来世界各国工业和经济的迅速发展,人类活动排入大气中的有害气体日益增多,引起了诸如“温室效应”、“平流层臭氧减少”、“酸雨”等危及人类生存条件、促使生态环境发生巨大变化的全球性环境污染问题。大气本底污染监测受到了世界气象组织(WMO)、世界卫生组织(WHO)和联合国环境计 相似文献
9.
向平流层注入硫化物粒子以抵消全球增暖的想法曾引起许多讨论。新的研究表明,该做法可能会对保护地球的臭氧层产生重大影响,延缓南极臭氧洞的恢复,并引起北极臭氧严重损失。该研究由NCAR的Simone Tilmes主持,发表在2008年4月24日的Science Express上。文章指出,对地球实施人工降温的尝试可能会带来危险的副作用,虽然气候变化对人类是重大威胁,但是在实施全球性的地球工程行动（global geoengineering solution）之前,有必要进行更深入的研究。 相似文献
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针对当今全球性环境危机问题，阐述了地球系统科学、全球变化与可持续发展关系，提出只有积极地进行全球变化研究，才能很好地协调自然与社会的持续稳定发展。 相似文献
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We use the coupled atmosphere–ocean general circulation model ECHAM5/MPI-OM to investigate the transition from the present-day
climate to a modern Snowball Earth, defined as the Earth in modern geography with complete sea-ice cover. Starting from the
present-day climate and applying an abrupt decrease of total solar irradiance (TSI) we find that the critical TSI marking
the Snowball Earth bifurcation point is between 91 and 94% of the present-day TSI. The Snowball Earth bifurcation point as
well as the transition times are well reproduced by a zero-dimensional energy balance model of the mean ocean potential temperature.
During the transition, the asymmetric distribution of continents between the Northern and Southern Hemisphere causes heat
transports toward the more water-covered Southern Hemisphere. This is accompanied by an intensification of the southern Hadley
cell and the wind-driven subtropical ocean cells by a factor of 4. If we set back TSI to 100% shortly before the transition
to a modern Snowball Earth is completed, a narrow band of open equatorial water is sufficient for rapid melting. This implies
that for 100% TSI the point of unstoppable glaciation separating partial from complete sea-ice cover is much closer to complete
sea-ice cover than in classical energy balance models. Stable states can have no greater than 56.6% sea-ice cover implying
that ECHAM5/MPI-OM does not exhibit stable states with near-complete sea-ice cover but open equatorial waters. 相似文献
12.
Guillaume Le Hir Yannick Donnadieu Gerhard Krinner Gilles Ramstein 《Climate Dynamics》2010,35(2-3):285-297
The current state of knowledge suggests that the Neoproterozoic snowball Earth is far from deglaciation even at 0.2 bars of CO2. Since understanding the termination of the fully ice-covered state is essential to sustain, or not, the snowball Earth theory, we used an Atmospheric General Climate Model (AGCM) to explore some key factors which could induce deglaciation. After testing the models’ sensitivity to their parameterizations of clouds, CO2 and snow, we investigated the warming effect caused by a dusty surface, associated with ash release during a mega-volcanic eruption. We found that the snow aging process, its dirtiness and the ash deposition on the snow-free ice are key factors for deglaciation. Our modelling study suggests that, under a CO2 enriched atmosphere, a dusty snowball Earth could reach the deglaciation threshold. 相似文献
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Responses of ocean circulation and ocean carbon cycle in the course of a global glaciation from the present Earth conditions are investigated by using a coupled climate-biogeochemical model. We investigate steady states of the climate system under colder conditions induced by a reduction of solar constant from the present condition. A globally ice-covered solution is obtained under the solar constant of 92.2% of the present value. We found that because almost all of sea water reaches the frozen point, the ocean stratification is maintained not by temperature but by salinity just before the global glaciation (at the solar constant of 92.3%). It is demonstrated that the ocean circulation is driven not by the surface cooling but by the surface freshwater forcing associated with formation and melting of sea ice. As a result, the deep ocean is ventilated exclusively by deep water formation in southern high latitudes where sea ice production takes place much more massively than northern high latitudes. We also found that atmospheric CO2 concentration decreases through the ocean carbon cycle. This reduction is explained primarily by an increase of solubility of CO2 due to a decrease of sea surface temperature, whereas the export production weakens by 30% just before the global glaciation. In order to investigate the conditions for the atmospheric CO2 reduction to cause global glaciations, we also conduct a series of simulations in which the total amount of carbon in the atmosphere?Cocean system is reduced from the present condition. Under the present solar constant, the results show that the global glaciation takes place when the total carbon decreases to be 70% of the present-day value. Just before the glaciation, weathering rate becomes very small (almost 10% of the present value) and the organic carbon burial declines due to weakened biological productivity. Therefore, outgoing carbon flux from the atmosphere?Cocean system significantly decreases. This suggests the atmosphere?Cocean system has strong negative feedback loops against decline of the total carbon content. The results obtained here imply that some processes outside the atmosphere?Cocean feedback loops may be required to cause global glaciations. 相似文献
14.
L. G. Bell 《Theoretical and Applied Climatology》2003,74(3-4):245-253
Summary ?Evidence is presented for a previously unknown climate cycle of 30,000 yr period. The cycle is deemed to be related to the
gyroscopic precession, or wobble of the Earth axis. Since it inhibits glaciation, the 30,000 yr cycle is called the summer
cycle while its counterpart, the 22,000 yr “precession” cycle, is the winter cycle. Because of the aspect presented to the
Sun, summer is effectively longer than winter. This is used to explain the difference between summer and winter cycle periods
and that of the wobble. Some of the problems encountered in interpreting oxygen ratio glaciation data are resolved by knowledge
of the existence of the summer cycle and a means is devised for determining the relative volume of glacial ice. An argument
is made that essentially eliminates the 100,000 yr-orbit cycle, by itself or in combination with other attitude cycles, as
a possible cause of the glacial/interglacial cycles.
Received August 17, 2002; accepted September 3, 2002 相似文献
15.
Prof. Dr. R. S. Lindzen 《Meteorology and Atmospheric Physics》1988,38(1-2):42-49
Summary In an earlier paper (Lindzen, 1986), it was shown that allowing CO2 to vary with snow/sea ice position could lead to a greatly enhanced response in glaciation to 100 K year orbital forcing—even when 20 K year forcing was much stronger. In that model, snow/sea ice position (SSIP) and glaciation were different: the former was the forcing for the latter. However, SSIP and glaciation were not decorrelated. Observations (Berner et al., 1979; Lorius et al., 1985; Neftel et al., 1982) suggest that CO2 may be independently related to both SSIP and glaciation. In the present paper, we allow (in a highly simplified manner) such independent dependence, and show how it alters the earlier results. Briefly, the dependence of CO2 on glaciation can contribute to and even cause a highly enhanced response to the 100 K year component of the forcing. However, the CO2 dependence on SSIP is, on the whole, more effective in this regard. Thus, we expect time series of CO2 to show variation on the faster time scales than does glaciation.With 5 Figures 相似文献
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In the 20th century on the territory of the northern slope of the Greater Caucasus the number of glaciers increased by 245 (or by 19%) and the glaciation area decreased by 849 km2 (or by 52.6%). It is revealed that the increase in the number of glaciers occurred as a result of the disintegration of larger glaciers into smaller parts and as a result of the cutoff of their tributaries, and the decrease in the glaciation area, due to the negative balance of the mass of glaciers. The length of all glaciers decreased by 128–3520 m during that period. It is demonstrated that in 1970–2011 the decrease in the glaciation area occurred with the rate being smaller than in 1895–1970 by 1.6 times that is associated with more favorable climatic conditions in 1970–2011. According to the computations of the climate model by the Main Geophysical Observatory (moderate scenario) for 2011–2099, average annual air temperature will increase by 1.06–2.70°C and the annual amount of precipitation, by 2.09–2.77%. According to the results of computations, the glaciation area in 2011–2099 will reduce by 585 km2 or by 76.5%. In the region under consideration, glaciation with the area of 180 km2 which will be concentrated only in the central part of the Greater Caucasus will maintain by 2099. The glacier runoff will decrease by 74–80%. 相似文献
17.
液态水含量和冰晶浓度对闪电频数影响的数值模拟研究 总被引：4，自引：1，他引：4
假定在软雹和冰晶碰撞的非感应起电机制为主要的起电机制成立的条件下，数值模拟研究了国际上公认的Fletcher和H—M冰晶产生机制以及云中的液态水含量对雷暴云放电过程（区分了云闪和地闪）的影响。结果表明，随着气压和温度的变化，在两种冰晶产生机制假定下，冰晶浓度分布有很大差异，这直接导致了雷暴云内电活动的差异。液态水含量的增加将使得首次放电时间延迟，同时将引起放电位置的下降和闪电频数的减少。 相似文献
18.
For over twenty years it has been known that energy balance models (EBMs) with snow-albedo feedback are characterized by unstable behavior in some areas of parameter space. This behavior leads to rapid changes in snow area due to small changes in forcing, and has been termed the small ice cap instability (SICI). It has never been clarified whether this behaviour reflects a real feature of the climate system or a limitation in EBMs. In this study we demonstrate that evidence for similar unstable behavior can also be found in an atmospheric general circulation model (GCM), using a realistic set of boundary conditions for the Carboniferous (300 Ma), one of the most extensive periods of glaciation in Earth history. When solar luminosity is sequentially lowered to near values appropriate for the Carboniferous, there is a discontinuous increase in summer snow area. The instability occurs in approximately the same area of parameter space as one previously found in an EBM. Analysis of selected fields indicates that the circulation is primarily affected in the area of snow increase; far-field effects are minimal. There is good agreement between model-generated summer snowcover and one reconstruction of Carboniferous ice cover. Although more work is required on this topic, our results provide increased support for the possibility that the snowline instability represents a real feature of the climate system, and that it may help explain some cases of glacial inception and abrupt transitions in Earth history. 相似文献
19.
The impact of atmospheric and oceanic heat transports on the sea-ice-albedo instability during the Neoproterozoic 总被引：1，自引：0，他引：1
In order to simulate the climatic conditions of the Neoproterozoic, we have conducted a series of simulations with a coupled ocean–atmosphere model of intermediate complexity, CLIMBER-2, using a reduced solar constant of 6% and varied CO2 concentrations. We have also tested the impact of the breakup of the supercontinent Rodinia that has been hypothesized to play an important role in the initiation of an ice-covered Earth. Our results show that for the critical values of 89 and 149 ppm of atmospheric CO2, a snowball Earth occurs in the supercontinent case and in the dislocated configuration, respectively. The study of the sensitivity of the meridional oceanic energy transport to reductions in CO2 concentration and to the dislocation of the supercontinent demonstrates that dynamics ocean processes can modulate the CO2 threshold value, below which a snowball solution is found, but cannot prevent it. The collapse of the overturning cells and of the oceanic heat transport is mainly due to the reduced zonal temperature gradient once the sea-ice line reaches the 30° latitudinal band but also to the freshening of the tropical ocean by sea-ice melt. In term of feedbacks, the meridional atmospheric heat transport via the Hadley circulation plays the major role, all along the CO2 decrease, by increasing the energy brought in the front of the sea-ice margin but does not appear enough efficient to prevent the onset of the sea-ice-albedo instability in the case of the continental configurations tested in this contribution. 相似文献
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Gareth S. Jones Jonathan M. Gregory Peter A. Stott Simon F. B. Tett Robert B. Thorpe 《Climate Dynamics》2005,25(7-8):725-738
Volcanic ‘super-eruptions’ have been suggested to have significantly influenced the Earth’s climate, perhaps causing glaciations
and impacting on the human population. Climatic changes following a hypothetical ‘super-eruption’ are simulated using a coupled
atmosphere ocean general circulation model, incorporating scaled volcanic stratospheric aerosols. Assumptions are made about
the stratospheric sulphate aerosol loading, size distribution, lifetime, chemical make up and spatial distribution. As this
study is concentrating on the physical climatological impacts over long timescales, microphysics and chemical interactive
processes are not simulated. Near-surface temperatures fall by as much as 10 K globally for a few months and a considerable
deviation from normal temperatures continues for several decades. A warming pattern is evident over northern land masses during
the winter due to increased longwave forcing and a positive AO mode. The overturning rate of the North Atlantic thermohaline
circulation doubles in intensity. Snow and ice increases in extent to a maximum coverage of 35% of the Earth. Despite these
and other impacts longer term climatic changes that could lead to a transition to a glaciation do not occur, for present day
boundary conditions and one possible plausible aerosol loading. 相似文献