Dynamics of recent climate change in the Arctic

The pattern of recent surface warming observed in the Arctic exhibits both polar amplification and a strong relation with trends in the Arctic Oscillation mode of atmospheric circulation. Paleoclimate analyses indicate that Arctic surface temperatures were higher during the 20th century than during the preceding few centuries and that polar amplification is a common feature of the past. Paleoclimate evidence for Holocene variations in the Arctic Oscillation is mixed. Current understanding of physical mechanisms controlling atmospheric dynamics suggests that anthropogenic influences could have forced the recent trend in the Arctic Oscillation, but simulations with global climate models do not agree. In most simulations, the trend in the Arctic Oscillation is much weaker than observed. In addition, the simulated warming tends to be largest in autumn over the Arctic Ocean, whereas observed warming appears to be largest in winter and spring over the continents.     

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.     

Role of seasonality in the evolution of climate during the last 100 million years

A simple climate model has been used to calculate the effect of past changes in the land-sea distribution on the seasonal cycle of temperatures during the last 100 million years. Modeled summer temperatures decreased over Greenland by more than 10 degrees C and over Antarctica by 5 degrees to 8 degrees C. For the last 80 million years, this thermal response is comparable in magnitude to estimated atmospheric carbon dioxide effects. Analysis of paleontological data provides some support for the proposed hypothesis that large changes due to seasonality may have sometimes resulted in an ice-free state due to high summer temperature rather than year-round warmth. Such "cool" non-glacials may have prevailed for as much as one-third of the last 100 million years.     

Causes of climate change over the past 1000 years

Recent reconstructions of Northern Hemisphere temperatures and climate forcing over the past 1000 years allow the warming of the 20th century to be placed within a historical context and various mechanisms of climate change to be tested. Comparisons of observations with simulations from an energy balance climate model indicate that as much as 41 to 64% of preanthropogenic (pre-1850) decadal-scale temperature variations was due to changes in solar irradiance and volcanism. Removal of the forced response from reconstructed temperature time series yields residuals that show similar variability to those of control runs of coupled models, thereby lending support to the models' value as estimates of low-frequency variability in the climate system. Removal of all forcing except greenhouse gases from the approximately 1000-year time series results in a residual with a very large late-20th-century warming that closely agrees with the response predicted from greenhouse gas forcing. The combination of a unique level of temperature increase in the late 20th century and improved constraints on the role of natural variability provides further evidence that the greenhouse effect has already established itself above the level of natural variability in the climate system. A 21st-century global warming projection far exceeds the natural variability of the past 1000 years and is greater than the best estimate of global temperature change for the last interglacial.     

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。     

扎龙湿地近50年温度和降水年际变化分析

研究基于扎龙湿地1955～2004年逐日气温和降水量资料,采用滑动平均、趋势分析、小波变换和Mann-Kendall检验等方法,探讨了扎龙湿地近50年的气候变化特征。结果表明,研究时段内扎龙湿地年及四季平均气温均呈上升的趋势,年平均气温在1988年发生了一次明显的突变,其后气温达到一个更显著的增暖时期,90年代以来的增温非常显著,该时期是50年以来的最高温期。扎龙湿地年及各季降水量除春季外均呈减少趋势,以秋季降水减少最为明显,研究时段内无明显的突变过程。扎龙湿地未来几年气候存在着向暖干期变化的可能性。     

48,000 years of climate and forest change in a biodiversity hot spot

A continuous 48,000-year-long paleoecological record from Neotropical lower montane forest reveals a consistent forest presence and an ice-age cooling of approximately 5 degrees to 9 degrees C. After 30,000 years of compositional stability, a steady turnover of species marks the 8000-year-long transition from ice-age to Holocene conditions. Although the changes were directional, the rates of community change were no different during this transitional period than in the preceding 30,000-year period of community stability. The warming rate of about 1 degrees C per millennium during the Pleistocene-Holocene transition was an order of magnitude less than the projected changes for the 21st century.     

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.     

Tropical temperature variations since 20,000 years ago: modulating interhemispheric climate change

Tropical sea surface temperatures (SSTs), as thermodynamically recorded in Barbados corals, were 5 degrees C colder than present values 19,000 years ago. Variable tropical SSTs may explain the interhemispheric synchroneity of global climate change as recorded in ice cores, snowline reconstructions, and vegetation records. Radiative changes due to cloud type and cloud cover are plausible mechanisms for maintaining cooler tropical SSTs in the past.     

Glaciation in taylor valley, antarctica, older than 2.7 million years

Potassium-argon dates for three samples of basaltic scoria from Taylor Valley, on the west side of McMurdo Sound, indicate that the basalt, which antedates and postdates major glaciations, is at least 2.7 million years old.     

近50年中国东北地区气候变化对农业的影响

在回顾中国学者关于东北地区气候变化及对农业影响研究成果基础上,系统概括分析了近50年东北地区农业气候资源和灾害的变化特征及气候变化对农业的影响特征。近50年东北地区升温明显,生长季热量资源增加;农业可用水资源和光能资源呈不同程度减少趋势,且时空分布不均。霜冻害、低温冷害、寒潮、洪涝、冰雹等农业气象灾害减少,旱灾增加。东北地区气候变化对农业影响总体有利,表现为作物适宜生育期延长,发育进程加快,全生育期缩短;积温增加且积温带北移东扩明显,主栽作物适宜种植区域扩大;作物品种由中晚熟替换早中熟;作物种植格局的变化为玉米、水稻、马铃薯等喜温作物种植面积扩大,春小麦种植面积减小。在水分为非限制因子的农区,作物气候生产潜力和产量为增加趋势。气候变化对农业影响的研究存在较大的不确定性,有必要针对农业气候变化及其对农业影响等开展系统性研究。     

Small bilaterian fossils from 40 to 55 million years before the cambrian

Ten phosphatized specimens of a small (<180 micrometers) animal displaying clear bilaterian features have been recovered from the Doushantuo Formation, China, dating from 40 to 55 million years before the Cambrian. Seen in sections, this animal (Vernanimalcula guizhouena gen. et sp. nov.) had paired coeloms extending the length of the gut; paired external pits that could be sense organs; bilateral, anterior-posterior organization; a ventrally directed anterior mouth with thick walled pharynx; and a triploblastic structure. The structural complexity is that of an adult rather than a larval form. These fossils provide the first evidence confirming the phylogenetic inference that Bilateria arose well before the Cambrian.     

Seawater strontium isotopic variations from 2.5 million years ago to the present

Measurements of marine carbonate samples indicate that during the past 2.5 million years the (87)Sr/(86)Sr ratio of seawater has increased by 14 x 10(-5). The high average rate of increase of (87)Sr/(86)Sr indicates that continental weathering rates were exceptionally high. Nonuniformity in the rate of increase suggests that weathering rates fluctuated by as much as +/-30 percent of present-day values. Some of the observed shifts in weathering rates are contemporaneous with climatic changes inferred from records of oxygen isotopes and carbonate preservation in deep sea sediments.     

气候变化背景下鄂州市近60年气温变化特征分析

基于鄂州市1959—2018年逐日气温资料,应用一元线性回归、Mann-Kendall突变检验结合累积距平法、小波分析等方法对鄂州市近60年平均气温、平均最高气温、平均最低气温、极端最高气温和极端最低气温变化特征进行统计分析。结果表明,鄂州市近60年平均气温、平均最高气温、平均最低气温、极端最高气温和极端最低气温都呈波动上升趋势,平均最低气温和极端最低气温的上升趋势相对于平均最高气温和极端最高气温的上升趋势更为明显;年平均气温无明显突变;年平均最高气温在2002年发生突变;年平均最低气温在1989年发生突变;年极端最高气温在2008年发生突变;年极端最低气温在1981年发生突变;年平均气温表现为准18年、准10年的年代际周期和准4年尺度的年际周期;年平均最高气温表现为准16年的年代际周期和准4年尺度的年际周期;年平均最低气温表现为准30年、准18年和准10年的年代际周期以及准4年的年际周期;极端最高气温表现为准12年的年代际周期和4～6年及2～4年的年际周期;极端最低气温表现为准30年、准16年和准10年的年代际周期以及准6年和准4年的年际周期。     

High-resolution Greenland ice core data show abrupt climate change happens in few years

The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.