Impacts of external forcing on the 20th century global warming

The impacts of external forcing,including natural and anthropogenic,on the 20th century global warming were assessed with the use of the Grid Atmospheric Model of IAP/LASG Version 1.1.0,fol-lowing the standard coordinated experiment design of the Climate Variability and Predictability(CLIVAR) International Climate of the Twentieth Century Project(C20C) ,Phase II. The results indicate that external forcing plays an important role in the evolution of the land surface air temperature on in-terannual,decadal,and interdecadal time scales,and contributes greatly to the global warming in the following two periods:the early twentieth century between the 1910s and the 1940s and the late twen-tieth century after the 1970s. External forcing also has strong impact on the regional temperature change during the two warming periods except for parts of the Eurasia and the North America conti-nents. In the cooling period,however,the impact of internal variability is dominant.     

Estimation on the response of glaciers in China to the global warming in the 21st century

Glaciers in China can be categorized into 3 types, i.e. the maritime (temperate) type, sub-continental (sub-polar) type and extreme Continental (polar) type, which take 22%, 46% and 32% of the total existing glacier area (59 406 km2) respectively. Researches indicate that glaciers of the three types show different response patterns to the global warming. Since the Maxima of the Little Ice Age (the 17th century), air temperature has risen at a magnitude of 1.3℃on average and the glacier area decreased corresponds to 20% of the present total glacier area in western China. it is estimated that air temperature rise in the 2030s, 2070s and 2100s will be of the order of 0.4-1.2, 1.2-2.7 and 2.1-4.0 K in western China. With these scenarios, glaciers in China will suffer from further shrinkage by 12%, 28% and 45% by the 2030s, 2070s and 2100s. The uncertainties may account for 30%-67% in 2100 in China.     

Widespread amphibian extinctions from epidemic disease driven by global warming

As the Earth warms, many species are likely to disappear, often because of changing disease dynamics. Here we show that a recent mass extinction associated with pathogen outbreaks is tied to global warming. Seventeen years ago, in the mountains of Costa Rica, the Monteverde harlequin frog (Atelopus sp.) vanished along with the golden toad (Bufo periglenes). An estimated 67% of the 110 or so species of Atelopus, which are endemic to the American tropics, have met the same fate, and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis) is implicated. Analysing the timing of losses in relation to changes in sea surface and air temperatures, we conclude with 'very high confidence' (> 99%, following the Intergovernmental Panel on Climate Change, IPCC) that large-scale warming is a key factor in the disappearances. We propose that temperatures at many highland localities are shifting towards the growth optimum of Batrachochytrium, thus encouraging outbreaks. With climate change promoting infectious disease and eroding biodiversity, the urgency of reducing greenhouse-gas concentrations is now undeniable.     

人类影响引起全球变暖的证据

 按照归因分析的研究方法和工具,综述了近些年有关人类影响引起全球变暖证据的科学研究成果。利用全球气候模式考虑人类影响,采用指纹法检测和归因证实,发现人类影响几乎肯定是引起近百年特别是近50年全球变暖的主因。地球系统5个圈层（大气、海洋、陆地、冰雪、生物）与全球变暖有关的证据,如热浪增加、寒潮减弱、低层大气变暖、陆地和海洋变暖、受海水热膨胀和冰融化引起全球海平面上升、冰雪和永冻土融化加速、海洋酸度增加、植物生长季延长等,都与人类影响有密切联系。     

Origins and estimates of uncertainty in predictions of twenty-first century temperature rise

Predictions of temperature rise over the twenty-first century are necessarily uncertain, both because the sensitivity of the climate system to changing atmospheric greenhouse-gas concentrations, as well as the rate of ocean heat uptake, is poorly quantified and because future influences on climate-of anthropogenic as well as natural origin-are difficult to predict. Past observations have been used to help constrain the range of uncertainties in future warming rates, but under the assumption of a particular scenario of future emissions. Here we investigate the relative importance of the uncertainty in climate response to a particular emissions scenario versus the uncertainty caused by the differences between future emissions scenarios for our estimates of future change. We present probabilistic forecasts of global-mean temperatures for four representative scenarios for future emissions, obtained with a comprehensive climate model. We find that, in the absence of policies to mitigate climate change, global-mean temperature rise is insensitive to the differences in the emissions scenarios over the next four decades. We also show that in the future, as the signal of climate change emerges further, the predictions will become better constrained.     

Eocene global warming events driven by ventilation of oceanic dissolved organic carbon

'Hyperthermals' are intervals of rapid, pronounced global warming known from six episodes within the Palaeocene and Eocene epochs (～65-34 million years (Myr) ago). The most extreme hyperthermal was the ～170 thousand year (kyr) interval of 5-7 °C global warming during the Palaeocene-Eocene Thermal Maximum (PETM, 56?Myr ago). The PETM is widely attributed to massive release of greenhouse gases from buried sedimentary carbon reservoirs, and other, comparatively modest, hyperthermals have also been linked to the release of sedimentary carbon. Here we show, using new 2.4-Myr-long Eocene deep ocean records, that the comparatively modest hyperthermals are much more numerous than previously documented, paced by the eccentricity of Earth's orbit and have shorter durations (～40?kyr) and more rapid recovery phases than the PETM. These findings point to the operation of fundamentally different forcing and feedback mechanisms than for the PETM, involving redistribution of carbon among Earth's readily exchangeable surface reservoirs rather than carbon exhumation from, and subsequent burial back into, the sedimentary reservoir. Specifically, we interpret our records to indicate repeated, large-scale releases of dissolved organic carbon (at least 1,600 gigatonnes) from the ocean by ventilation (strengthened oxidation) of the ocean interior. The rapid recovery of the carbon cycle following each Eocene hyperthermal strongly suggests that carbon was re-sequestered by the ocean, rather than the much slower process of silicate rock weathering proposed for the PETM. Our findings suggest that these pronounced climate warming events were driven not by repeated releases of carbon from buried sedimentary sources, but, rather, by patterns of surficial carbon redistribution familiar from younger intervals of Earth history.     

Response of monsoon variability in Himalayas to global warming

Reconstructed annual net accumulation from the Dasuopu ice core recovered in Himalayas, with a good correlation to Indian monsoon, reflects a major precipitation trend in central Himalayas. The Dasuopu accumulation (DSP An) also shows a strong correlation to the Northern Hemispheric temperature. Generally, as the Northern Hemispheric temperature increases by 0.1 K, the accumulation decreases by about 90 mm and vise versa. Under the condition of global warming, especially since 1920, the Northern Hemispheric mean temperature has increased by about 0.5 K, whereas accumulation in Dasuopu ice core has decreased by about 450 mm. According to the relationship between accumulation and temperature, a scenario prediction of monsoon rainfall in central Himalayas is made.     

湖北地区气温变化对全球变暖的响应

选用湖北省77个代表站1960-2003年逐日气温观测资料,分析了湖北省气温的年、季节变化规律及其地域分布特征．结果表明：湖北省近44年气温呈上升趋势,至2003年气温上升了0．5℃,增温速率约为0．12℃／10a,和近50年来的全球平均增温速率相当．20世纪90年代升温最剧烈．春季、秋季和冬季气温均呈上升趋势,冬季增温最明显,而夏季气温却呈下降趋势．夏季平均日最高气温也呈下降趋势,冬季平均日最低气温上升趋势显著．气温变化不同的地区差异较大,西部地区变化趋势不明显,有微弱的下降趋势,而中东部地区则有较明显的升温趋势．     

Fingerprints of global warming on wild animals and plants

Over the past 100 years, the global average temperature has increased by approximately 0.6 degrees C and is projected to continue to rise at a rapid rate. Although species have responded to climatic changes throughout their evolutionary history, a primary concern for wild species and their ecosystems is this rapid rate of change. We gathered information on species and global warming from 143 studies for our meta-analyses. These analyses reveal a consistent temperature-related shift, or 'fingerprint', in species ranging from molluscs to mammals and from grasses to trees. Indeed, more than 80% of the species that show changes are shifting in the direction expected on the basis of known physiological constraints of species. Consequently, the balance of evidence from these studies strongly suggests that a significant impact of global warming is already discernible in animal and plant populations. The synergism of rapid temperature rise and other stresses, in particular habitat destruction, could easily disrupt the connectedness among species and lead to a reformulation of species communities, reflecting differential changes in species, and to numerous extirpations and possibly extinctions.     

Multimodel projections and uncertainties of net ecosystem production in China over the twenty-first century

Ecosystems in China have been absorbing anthropogenic CO2 over the last three decades. Here, we assess future carbon uptake in China using models from phase 5 of Coupled Model Intercomparison Project under four socio-economic scenarios. The average of China＇s carbon sink from 2006 to 2100 represented by multimodel mean net ecosystem production （NEP） is projected to increase （relative to averaged NEP from 1976 to 2005） in the range of 0.137 and 0.891 PgC a^-1 across different scenarios. Increases in NEP are driven by increases in net primary production exceeding increases in heterotrophic respiration, and future carbon sink is mainly attributed to areas located in eastern China. However, there exists a considerable model spread in the magnitude of carbon sink and model spread tends to be larger when future climate change becomes more intense. The model spread may result from intermodel discrepancy in the magnitude of CO2 fertilization effect on photosynthesis, soil carbon turnover time, presence of carbon-nitrogen cycle and interpretation of land-use changes. For better quantifying future carbon cycle, a research priority toward improving model representation of these processes is recommended.     

全球变暖背景下极端降水变化率与气温的响应关系

以中国整体为研究区,基于1960—2013年520个气象站逐日降水和气温数据,选取极端降水变化率(α)和饱和水汽压变化率(β)2个指标,定量分析了极端降水与全球变暖之间的内在联系.结果表明:全球变暖背景下我国整体上极端降水呈现增加的趋势,α和β分别为6.4%·℃-1和9.3%·℃-1,且α更接近理论值(约7%·℃-1),β与平均气温存在指数定量化关系.在此基础上,根据平均气温的不同将我国划分为9个对照组,进一步分析其空间差异,结果表明:α和β在空间上存在显著的正相关关系(r=0.63),具体表现为平均气温较高的地区,α和β值也较大.证明了饱和水汽压随温度的变化率可以从大尺度上解释极端降水增加的空间变化特征.     

全球变暖背景下大连地区寒潮活动的气候变化

利用1961~2005年大连地区6个气象观测站的逐日平均气温、最低气温和最大平均风力资料,分析近45年大连地区寒潮活动的气候特征,着重研究大连地区寒潮的年代际、年际变化.结果表明:大连地区寒潮活动各地差异较大,南部开始早,结束晚;东部开始晚,结束早.大连地区寒潮主要出现在11、12月和1月.近45年来,大连地区寒潮异常具有三次跃变,跃变发生在20世纪70年代中期、80年代中后期和21世纪初期.大连的寒潮活动也可以分为四个阶段:活跃期—沉寂期—正负振荡期—沉寂期.近45年来,大连地区寒潮活动具有减少的趋势,从1961~2005年,趋势性寒潮频数减少为0.7次/10年.     

智能机器人:21世纪科技皇冠上的璀璨明珠

 在回顾智能机器人发展历程的基础上,阐述了机器人的过去:人类的幻想,机器人的现在:从幻想走向现实,机器人的未来:智能机器人。介绍了工业机器人、军用机器人、仿生机器人、服务机器人、多指灵巧手和类人机器人的主要功能、研究现状和应用背景。展望了智能机器人的发展前景。     

Astronomical pacing of late Palaeocene to early Eocene global warming events

At the boundary between the Palaeocene and Eocene epochs, about 55 million years ago, the Earth experienced a strong global warming event, the Palaeocene-Eocene thermal maximum. The leading hypothesis to explain the extreme greenhouse conditions prevalent during this period is the dissociation of 1,400 to 2,800 gigatonnes of methane from ocean clathrates, resulting in a large negative carbon isotope excursion and severe carbonate dissolution in marine sediments. Possible triggering mechanisms for this event include crossing a threshold temperature as the Earth warmed gradually, comet impact, explosive volcanism or ocean current reorganization and erosion at continental slopes, whereas orbital forcing has been excluded. Here we report a distinct carbonate-poor red clay layer in deep-sea cores from Walvis ridge, which we term the Elmo horizon. Using orbital tuning, we estimate deposition of the Elmo horizon at about 2 million years after the Palaeocene-Eocene thermal maximum. The Elmo horizon has similar geochemical and biotic characteristics as the Palaeocene-Eocene thermal maximum, but of smaller magnitude. It is coincident with carbon isotope depletion events in other ocean basins, suggesting that it represents a second global thermal maximum. We show that both events correspond to maxima in the approximately 405-kyr and approximately 100-kyr eccentricity cycles that post-date prolonged minima in the 2.25-Myr eccentricity cycle, implying that they are indeed astronomically paced.     

Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model

The continued increase in the atmospheric concentration of carbon dioxide due to anthropogenic emissions is predicted to lead to significant changes in climate. About half of the current emissions are being absorbed by the ocean and by land ecosystems, but this absorption is sensitive to climate as well as to atmospheric carbon dioxide concentrations, creating a feedback loop. General circulation models have generally excluded the feedback between climate and the biosphere, using static vegetation distributions and CO2 concentrations from simple carbon-cycle models that do not include climate change. Here we present results from a fully coupled, three-dimensional carbon-climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a 'business as usual' scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5 Gt C yr(-1) is balanced by the terrestrial carbon source, and atmospheric CO2 concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models, resulting in a global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle feedback.     

Recognition of climatic effects of land use/land cover change under global warming

Greenhouse gas emissions and land use/land cover change (LUCC) are two human activities notably affecting climate change. Will temperature and precipitation increase significantly during global warming resulting in more pronounced LUCC climatic effects? Considering the interannual forcing of these two factors, the NCAR Community Atmosphere Model (CAM4.0) was used in this study to investigate the importance of climatological background to LUCC impacts. Experiments based on the difference in the background climate, the greenhouse gas concentrations in 1850 and in the present age indicate contrary changes in climate sensitivity through estimations of the radiative forcing associated with LUCC, which are 0.54°C/(W/m²) and ?0.26°C/(W/m²), respectively. Therefore, the background climate appears to play an important role in the regional impact of LUCC, especially at higher latitudes. In addition, global warming predominantly influences snow-albedo feedback in the mid-latitudes, thus determining the impact of LUCC, whereas the regional difference in precipitation caused by global warming is responsible for the differing climate response to LUCC in the tropics and subtropics.     

Numerical simulation of the sensitivity of the Pacific subtropical-tropical meridional cell to global warming

Sensitivity of the Pacific subtropical-tropical meridional cell to global warming is examined by using a global ocean-atmosphere coupled model developed at LASG/IAP. Results indicate that associated with the increasing of atmospheric carbon dioxide, the most prominent signals of global warming locate at high latitudes, and the change of middle and low latitudes, in particular the surface wind, is relatively weak, which leads to a weak response of the Pacific subtropical-tropical meridional cell. At the time of atmospheric carbon dioxide doubling, the change of the meridional cell strength is smaller than the amplitude of natural variability.     

Release of methane from a volcanic basin as a mechanism for initial Eocene global warming

A 200,000-yr interval of extreme global warming marked the start of the Eocene epoch about 55 million years ago. Negative carbon- and oxygen-isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid (approximately 10,000 yr) input of isotopically depleted carbon. It has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change. Large-scale hydrate melting, however, requires a hitherto unknown triggering mechanism. Here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the V?ring and M?re basins in the Norwegian Sea. We propose that intrusion of voluminous mantle-derived melts in carbon-rich sedimentary strata in the northeast Atlantic may have caused an explosive release of methane--transported to the ocean or atmosphere through the vent complexes--close to the Palaeocene/Eocene boundary. Similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the Siberian Traps (approximately 250 million years ago) and the Karoo Igneous Province (approximately 183 million years ago).