The evolution of climate over the last millennium

Knowledge of past climate variability is crucial for understanding and modeling current and future climate trends. This article reviews present knowledge of changes in temperatures and two major circulation features-El Ni?o-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO)-over much of the last 1000 years, mainly on the basis of high-resolution paleoclimate records. Average temperatures during the last three decades were likely the warmest of the last millennium, about 0.2 degrees C warmer than during warm periods in the 11th and 12th centuries. The 20th century experienced the strongest warming trend of the millennium (about 0.6 degrees C per century). Some recent changes in ENSO may have been unique since 1800, whereas the recent trend to more positive NAO values may have occurred several times since 1500. Uncertainties will only be reduced through more extensive spatial sampling of diverse proxy climatic records.     

Natural variability of Greenland climate, vegetation, and ice volume during the past million years

The response of the Greenland ice sheet to global warming is a source of concern notably because of its potential contribution to changes in the sea level. We demonstrated the natural vulnerability of the ice sheet by using pollen records from marine sediment off southwest Greenland that indicate important changes of the vegetation in Greenland over the past million years. The vegetation that developed over southern Greenland during the last interglacial period is consistent with model experiments, suggesting a reduced volume of the Greenland ice sheet. Abundant spruce pollen indicates that boreal coniferous forest developed some 400,000 years ago during the "warm" interval of marine isotope stage 11, providing a time frame for the development and decline of boreal ecosystems over a nearly ice-free Greenland.     

胶州地区近5年气候变化特征分析

利用近5年胶州地区自动气象观测站的监测资料,对胶州市的气候进行分析研究。研究表明：胶州市平均气温13.8℃;年平均降水量为535毫米,降水从5月份开始增多,8月份最多;平均风速3.0～5.2m/s,春季和冬季风速偏大,风向以东南风为主。通过对胶州市气候变化的特征分析和研究,为胶州市森林防火、生态建设等工作提供科学依据。     

Flood basalt volcanism during the past 250 million years

A chronology of the initiation dates of major continental flood basalt volcanism is established from published potassium-argon (K-Ar) and argon-argon (Ar-Ar) ages of basaltic rocks and related basic intrusions. The dating is therefore independent of the biostratigraphic and paleomagnetic time scales. Estimated errors of the initation dates of the volcanic episodes determined from the distributions of the radiometric ages are, approximately, plus or minus 4 percent. There were 11 distinct episodes during the past 250 million years. Sometimes appearing in pairs, the episodes have occurred quasi-periodically with a mean cycle time of 32 +/- 1 (estimated, error of the mean) million years. The initiation dates of the episodes are close to the estimated dates of mass extinctions of marine organisms. Showers of impacting comets may be the cause.     

Synchronous radiocarbon and climate shifts during the last deglaciation

Radiocarbon data from the Cariaco Basin provide calibration of the carbon-14 time scale across the period of deglaciation (15,000 to 10, 000 years ago) with resolution available previously only from Holocene tree rings. Reconstructed changes in atmospheric carbon-14 are larger than previously thought, with the largest change occurring simultaneously with the sudden climatic cooling of the Younger Dryas event. Carbon-14 and published beryllium-10 data together suggest that concurrent climate and carbon-14 changes were predominantly the result of abrupt shifts in deep ocean ventilation.     

2.8 million years of Arctic climate change from Lake El'gygytgyn, NE Russia

The reliability of Arctic climate predictions is currently hampered by insufficient knowledge of natural climate variability in the past. A sediment core from Lake El'gygytgyn in northeastern (NE) Russia provides a continuous, high-resolution record from the Arctic, spanning the past 2.8 million years. This core reveals numerous "super interglacials" during the Quaternary; for marine benthic isotope stages (MIS) 11c and 31, maximum summer temperatures and annual precipitation values are ~4° to 5°C and ~300 millimeters higher than those of MIS 1 and 5e. Climate simulations show that these extreme warm conditions are difficult to explain with greenhouse gas and astronomical forcing alone, implying the importance of amplifying feedbacks and far field influences. The timing of Arctic warming relative to West Antarctic Ice Sheet retreats implies strong interhemispheric climate connectivity.     

Abrupt climate oscillations during the last deglaciation in central north america

Evidence from stable isotopes and a variety of proxies from two Ontario lakes demonstrate that many of the late glacial-to-early Holocene events that are well known from the North Atlantic seaboard, such as the Gerzensee-Killarney Oscillation (also known as the Intra-Allerod Cold Period), Younger Dryas, and Preboreal Oscillation, also occurred in central North America. These results thus imply that climatic forcing acted in the same manner in both regions and that atmospheric circulation played an important role in the propagation of these events.     

Local orbital forcing of antarctic climate change during the last interglacial

During the last interglacial, Antarctic climate changed before that of the Northern Hemisphere. Large local changes in precession forcing could have produced this pattern if there were a rectified response in sea ice cover. Results from a coupled sea ice-ocean general circulation model supported this hypothesis when it was tested for three intervals around the last interglacial. Such a mechanism may play an important role in contributing to phase offsets between Northern and Southern Hemisphere climate change for other time intervals.     

近60年尚志市极端气温变化规律

选用世界气象组织（WMO）提供的6种极端气温指数对尚志市1953 201 2年近60年来逐日最高气温、最低气温资料数据进行计算和分析,得出了尚志市近60年来的极端气温变化规律.结果表明：近60年来,尚志市暖日和暖夜显著增多,分别以1.9 d/10a和3.7 d/10a的速度增加;冷日和冷夜显著减少,分别以1.9 d/10a和3.9 d/10a速度减少;年极端最高和最低气温分别以0.2 C/10a和0.6 C/10a速度显著升高;年极端低温升高趋势高于年极端高温,即夜间增暖幅度高于白天增暖幅度,夜间气温上升对增暖贡献更大.尚志市与黑龙江省极端气温比较发现,极端气温变化趋势一致,但增加和减少速度明显低于黑龙江省.     

Asynchronous climate changes in the North Atlantic and Japan during the last termination

Pollen records from the annually laminated sediment sequence in Lake Suigetsu, Japan, suggest a sequence of climate changes during the Last Termination that resembles that of the North Atlantic region but with noticeable differences in timing. An interstadial interval commenced a few centuries earlier [approximately 15,000 years before the present (yr B.P.)] than the North Atlantic GI-1 (B?lling) event. Conversely, the onset of a Younger Dryas (YD)-like cold reversal (12,300 to 11,250 yr B.P.) postdated the North Atlantic GS-1 (YD) event by a few centuries. Climate in the Far East during the Last Termination reflected solar insolation changes as much as Atlantic influences.     

Large variations in Southern Hemisphere biomass burning during the last 650 years

We present a 650-year Antarctic ice core record of concentration and isotopic ratios (δ(13)C and δ(18)O) of atmospheric carbon monoxide. Concentrations decreased by ~25% (14 parts per billion by volume) from the mid-1300s to the 1600s then recovered completely by the late 1800s. δ(13)C and δ(18)O decreased by about 2 and 4 per mil (‰), respectively, from the mid-1300s to the 1600s then increased by about 2.5 and 4‰ by the late 1800s. These observations and isotope mass balance model results imply that large variations in the degree of biomass burning in the Southern Hemisphere occurred during the last 650 years, with a decrease by about 50% in the 1600s, an increase of about 100% by the late 1800s, and another decrease by about 70% from the late 1800s to present day.     

The rise of oxygen over the past 205 million years and the evolution of large placental mammals

On the basis of a carbon isotopic record of both marine carbonates and organic matter from the Triassic-Jurassic boundary to the present, we modeled oxygen concentrations over the past 205 million years. Our analysis indicates that atmospheric oxygen approximately doubled over this period, with relatively rapid increases in the early Jurassic and the Eocene. We suggest that the overall increase in oxygen, mediated by the formation of passive continental margins along the Atlantic Ocean during the opening phase of the current Wilson cycle, was a critical factor in the evolution, radiation, and subsequent increase in average size of placental mammals.     

Seven million years of glaciation in greenland

Glacial till, glaciomarine diamictites, and ice-rafted detritus found in marine cores collected off the shore of southeast Greenland record multiple Late Cenozoic glaciations beginning in the Late Miocene. Distinct rock assemblages and seismic stratigraphic control correlate the diamictites with glaciation of the southeast Greenland margin. Glaciers advanced to the sea during several intervals in the Pliocene and Pleistocene. North Atlantic glaciation may have nucleated in southern Greenland rather than further north because of the high mountains and the high levels of precipitation in this region.     

Timing of millennial-scale climate change in Antarctica and Greenland during the last glacial period

A precise relative chronology for Greenland and West Antarctic paleotemperature is extended to 90,000 years ago, based on correlation of atmospheric methane records from the Greenland Ice Sheet Project 2 and Byrd ice cores. Over this period, the onset of seven major millennial-scale warmings in Antarctica preceded the onset of Greenland warmings by 1500 to 3000 years. In general, Antarctic temperatures increased gradually while Greenland temperatures were decreasing or constant, and the termination of Antarctic warming was apparently coincident with the onset of rapid warming in Greenland. This pattern provides further evidence for the operation of a "bipolar see-saw" in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales.     

Genome size in conodonts (chordata): inferred variations during 270 million years

DNA is too unstable to be preserved during fossilization, but it still seems possible to infer the genome content of fossils because in every group of organisms investigated cell size is proportional to quantity of DNA. Accordingly, information on macroevolutionary trends in genome size through millions of years is potentially available. This survey of inferred variation in genome content in fossils is based on measurements of epithelial cells in extinct conodonts over a period of 270 million years. Why genome size varies so widely amongst living organisms is a subject of continuing debate. Paleontology offers a distinct temporal perspective, but lack of data on conodont paleoecology make the proposed adaptive explanations for genome variation difficult to test.     

Evidence from Western north america for rapid shifts in climate during the last glacial maximum

The Estancia basin in southwestern United States contains evidence for strong and rapid pulsations in the supply of moisture brought into the region during the last ice age. The pulses were recorded during episodes of stream discharge that spread plumes of fresh water laden with quartz sand over the saline lake. The largest pulses in stream discharge lasted only a few decades, were organized into cycles that were spaced approximately 200 to 250 and 2000 years apart, and were of sufficient magnitude to freshen and maintain the lake at its maximum recorded elevation.     

Oxygen-18 content of atmospheric precipitation during last 11,000 years in the Great Lakes region

Freshwater lake marl and mollusks from Indiana show variations in ratios of oxygen-18 to oxygen-16 of a few per mil during the Postglacial. For the last 9000 years these variations are about 1 per mil for properly selected lake sediments. Thus the oxygen isotope composition of atmospheric precipitation appears relatively stable over this interval, indicating stationary atmospheric circulation patterns over the Great Lakes region. A reduction in oxygen-18 content around 10,000 years ago corresponds with the climate change indicated by pollen profiles. Large systematic differences were found between carbon-13 and oxygen-18 content of marl and mollusks.     

安徽省近50年极端低温事件的变化特征和季节性差异

基于安徽省17个观测站1962～2011年的逐日最低温度资料,利用百分位阈值法计算了各站极端低温事件,在此基础上使用线性趋势、Mann-Kendall和EOF方法对安徽省极端低温事件的变化特征进行了分析。结果表明安徽省极端低温事件的变化特征具有明显的季节性差异。总体上,年极端低温事件空间分布呈西多东少,北多南少,季节尺度上则表现为春、秋季南北多、中部少,夏、冬季西多东少。各站极端低温事件均表现为冬季最多、春秋次之、夏季最少的季节特征。年和四季极端低温事件均是皖东北减少最快,但减少最慢的区域各不相同,其中夏、秋季部分区域没有显著的变化趋势,其变化在空间上都具有一致性,均中部大、南北小。年及春、秋、冬季极端低温事件在20世纪60至70年代初总体以偏多为主,70至80年代偏多偏少相间,而夏季则变化幅度较大。90年代中期之后,年及四季极端低温事件均以偏少为主。年及春、秋、冬季极端低温事件在70年代之后均总体呈减少趋势,90年代左右开始显著减少,而夏季则在90年代中期之后才开始显著减少。另外春、秋季极端低温事件在80年代末出现了突变特征,而年及夏、冬季则表现出渐变的特征。     

Atmospheric CO2 and climate on millennial time scales during the last glacial period

Reconstructions of ancient atmospheric carbon dioxide (CO2) variations help us better understand how the global carbon cycle and climate are linked. We compared CO2 variations on millennial time scales between 20,000 and 90,000 years ago with an Antarctic temperature proxy and records of abrupt climate change in the Northern Hemisphere. CO2 concentration and Antarctic temperature were positively correlated over millennial-scale climate cycles, implying a strong connection to Southern Ocean processes. Evidence from marine sediment proxies indicates that CO2 concentration rose most rapidly when North Atlantic Deep Water shoaled and stratification in the Southern Ocean was reduced. These increases in CO2 concentration occurred during stadial (cold) periods in the Northern Hemisphere, several thousand years before abrupt warming events in Greenland.