Transient floral change and rapid global warming at the Paleocene-Eocene boundary

Rapid global warming of 5 degrees to 10 degrees C during the Paleocene-Eocene Thermal Maximum (PETM) coincided with major turnover in vertebrate faunas, but previous studies have found little floral change. Plant fossils discovered in Wyoming, United States, show that PETM floras were a mixture of native and migrant lineages and that plant range shifts were large and rapid (occurring within 10,000 years). Floral composition and leaf shape and size suggest that climate warmed by approximately 5 degrees C during the PETM and that precipitation was low early in the event and increased later. Floral response to warming and/or increased atmospheric CO2 during the PETM was comparable in rate and magnitude to that seen in postglacial floras and to the predicted effects of anthropogenic carbon release and climate change on future vegetation.     

Nannoplankton extinction and origination across the Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene Thermal Maximum (PETM, approximately 55 million years ago) was an interval of global warming and ocean acidification attributed to rapid release and oxidation of buried carbon. We show that the onset of the PETM coincided with a prominent increase in the origination and extinction of calcareous phytoplankton. Yet major perturbation of the surface-water saturation state across the PETM was not detrimental to the survival of most calcareous nannoplankton taxa and did not impart a calcification or ecological bias to the pattern of evolutionary turnover. Instead, the rate of environmental change appears to have driven turnover, preferentially affecting rare taxa living close to their viable limits.     

Paleocene-Eocene thermal maximum and the opening of the Northeast Atlantic

The Paleocene-Eocene thermal maximum (PETM) has been attributed to a sudden release of carbon dioxide and/or methane. 40Ar/39Ar age determinations show that the Danish Ash-17 deposit, which overlies the PETM by about 450,000 years in the Atlantic, and the Skraenterne Formation Tuff, representing the end of 1 +/- 0.5 million years of massive volcanism in East Greenland, are coeval. The relative age of Danish Ash-17 thus places the PETM onset after the beginning of massive flood basalt volcanism at 56.1 +/- 0.4 million years ago but within error of the estimated continental breakup time of 55.5 +/- 0.3 million years ago, marked by the eruption of mid-ocean ridge basalt-like flows. These correlations support the view that the PETM was triggered by greenhouse gas release during magma interaction with basin-filling carbon-rich sedimentary rocks proximal to the embryonic plate boundary between Greenland and Europe.     

1961～2010年海南兴隆气候变化趋势与突变分析

利用趋势分析和Mann-kendall检验统计方法对海南省万宁市兴隆旅游经济区近50年(1961~2010年)降水量、气温和相对湿度等气象因子进行趋势分析和突变分析.结果表明:兴隆地区年平均温度呈明显上升趋势,变化倾向率约0.288℃/(10 a);年降水量变化整体变化呈下降趋势,但未能通过显著性检验;年平均相对湿度的变化整体上表现出下降趋势,变化倾向率为-1.052%/(10 a);兴隆地区年平均气温的自20世纪70年代起开始呈现升高趋势,到1990年左右发生了突变,但年降水量、相对湿度未发现突变点.综上所述,兴隆地区近50年来气候变化趋势与全国范围基本一致,增温幅度略高于全岛水平;而降水量变化趋势与海南岛相反,呈现出微弱的线性下降趋势.     

Radiative absorption enhancements due to the mixing state of atmospheric black carbon

Atmospheric black carbon (BC) warms Earth's climate, and its reduction has been targeted for near-term climate change mitigation. Models that include forcing by BC assume internal mixing with non-BC aerosol components that enhance BC absorption, often by a factor of ~2; such model estimates have yet to be clearly validated through atmospheric observations. Here, direct in situ measurements of BC absorption enhancements (E(abs)) and mixing state are reported for two California regions. The observed E(abs) is small-6% on average at 532 nm-and increases weakly with photochemical aging. The E(abs) is less than predicted from observationally constrained theoretical calculations, suggesting that many climate models may overestimate warming by BC. These ambient observations stand in contrast to laboratory measurements that show substantial E(abs) for BC are possible.     

The response of vegetation on the Andean flank in western Amazonia to Pleistocene climate change

A reconstruction of past environmental change from Ecuador reveals the response of lower montane forest on the Andean flank in western Amazonia to glacial-interglacial global climate change. Radiometric dating of volcanic ash indicates that deposition occurred ~324,000 to 193,000 years ago during parts of Marine Isotope Stages 9, 7, and 6. Fossil pollen and wood preserved within organic sediments suggest that the composition of the forest altered radically in response to glacial-interglacial climate change. The presence of Podocarpus macrofossils ~1000 meters below the lower limit of their modern distribution indicates a relative cooling of at least 5°C during glacials and persistence of wet conditions. Interglacial deposits contain thermophilic palms suggesting warm and wet climates. Hence, global temperature change can radically alter vegetation communities and biodiversity in this region.     

黄土高原半干旱区降水量对当地气候变化的响应

利用毛乌素沙漠边缘的丘陵沟壑区的观测站降水量资料,通过Mann-Kendall法等数理统计方法,分析陇东北部地区降水量对当地气候变化的响应特征。从56 a的降水量统计来看,降水呈现出逐年减少的趋势,其中年降水量、春季降水量、秋季降水量序列的线性倾向率分别为-7.36、-2.27、-6.35 mm/10 a,夏季降水量序列的线性倾向率为0.69 mm/10 a,这说明四季当中只有夏季降水量呈现出上升的变化趋势。通过对降水量的多时间尺度分析发现,年降水量存在着至少3个尺度的变化结构,主要的变换集中在5、10~15、25~30 a的尺度,在25~30 a的时间尺度上最为显著,降水量经历了偏多-偏少-偏多-偏少的交替变化,1970年前、1984~1997年降水量较多,1970~1984、1997~2007年降水量较少,2007年之后降水量又开始趋于增多,根据降水量的小波方差分析,确定25~30 a是降水量序列变化的第一主导周期。通过Mann-Kendall突变检验发现降水量在1968年之后减少的趋势明显,确定突变点为1968年。通过研究降水量与其他气象要素的相关性发现,夏季气温、秋季的日照时数,春季的地表温度伴随着相应时间段降水量的变化,均表现出负相关的变化特征,只有秋季降水量与相对湿度表现为正相关的变化规律。秋季相对湿度与降水量的变化关系最为密切,相关系数最大达到0.71,其后依次是秋季降水量和日照时数的0.60、春季降水量与地表温度的0.36,夏季气温与降水量的0.35。关系模型的建立说明通过降水量的变化情况在一定程度上可以反映出其他气象要素的变化规律,其共同影响着当地的气候环境。     

近50年来榆林市气候变化特征及其对气候生产力的影响研究

利用1961～2010年榆林市逐月气温、降水资料,分析了榆林市的气候变化特征;利用Thornthwaite Memorial模型计算了该区域气候生产力,通过二元回归模型分析了气候生产力的演变特征。结果表明:近50年来,榆林全年及四季平均气温均呈上升趋势,尤以冬季平均气温上升显著;降水量年际波动剧烈而总体变化趋势不大;de Martonne干燥度呈现下降趋势。气候生产力呈现微弱的增长趋势,年降水量是影响气候生产力的主要因素,其与气候生产力间存在极显著的正相关关系,当榆林年均气温上升1℃、年降水量上升1 mm时,榆林气候生产力将上升21.5 kg/(hm2.a)。     

Rapid acidification of the ocean during the Paleocene-Eocene thermal maximum

The Paleocene-Eocene thermal maximum (PETM) has been attributed to the rapid release of approximately 2000 x 10(9) metric tons of carbon in the form of methane. In theory, oxidation and ocean absorption of this carbon should have lowered deep-sea pH, thereby triggering a rapid (<10,000-year) shoaling of the calcite compensation depth (CCD), followed by gradual recovery. Here we present geochemical data from five new South Atlantic deep-sea sections that constrain the timing and extent of massive sea-floor carbonate dissolution coincident with the PETM. The sections, from between 2.7 and 4.8 kilometers water depth, are marked by a prominent clay layer, the character of which indicates that the CCD shoaled rapidly (<10,000 years) by more than 2 kilometers and recovered gradually (>100,000 years). These findings indicate that a large mass of carbon (>2000 x 10(9) metric tons of carbon) dissolved in the ocean at the Paleocene-Eocene boundary and that permanent sequestration of this carbon occurred through silicate weathering feedback.     

A transient rise in tropical sea surface temperature during the Paleocene-Eocene thermal maximum

The Paleocene-Eocene Thermal Maximum (PETM) has been attributed to a rapid rise in greenhouse gas levels. If so, warming should have occurred at all latitudes, although amplified toward the poles. Existing records reveal an increase in high-latitude sea surface temperatures (SSTs) (8 degrees to 10 degrees C) and in bottom water temperatures (4 degrees to 5 degrees C). To date, however, the character of the tropical SST response during this event remains unconstrained. Here we address this deficiency by using paired oxygen isotope and minor element (magnesium/calcium) ratios of planktonic foraminifera from a tropical Pacific core to estimate changes in SST. Using mixed-layer foraminifera, we found that the combined proxies imply a 4 degrees to 5 degrees C rise in Pacific SST during the PETM. These results would necessitate a rise in atmospheric pCO2 to levels three to four times as high as those estimated for the late Paleocene.     

北方森林生态系统对全球气候变化的响应研究进展

北方森林是地球上第2大生物群区,约占陆地森林面积的30%,提供了从局地到全球的生态系统服务功能。1850年以来,全球性持续升温不断显现,2000—2050年全球至少升高2 ℃,甚至更高。预计到2100年,北方森林区冬季平均温度将升高1.3~6.3 ℃。与此同时,几乎所有的北方森林生态系统功能都将会受到影响,尤其是近几十年来,该区域发生了很多与温度升高相关的潜在生态响应。本文从碳循环、生物多样性、干旱化和林火发生频率以及冻土变化等方面具体综述了北方森林生态系统对于全球气候变化的响应。响应结果如下:1)气候变化对于北方森林碳循环动态的影响是极其复杂的,迄今为止并没有达成共识, 分解对于温度的反应敏感程度至今仍存在很多不确定性。2)动物、植物和微生物(真菌)均对气候变化产生了一定的响应,表现为动物和植物的分布区进一步北移,但真菌的多样性和生产力响应机制尚无法确定。3)北方森林区随气候变化表现为进一步的干旱化和林火发生明显增加。4)北方森林区与冻土伴生,冻土随气候变暖表现出了面积缩小和活动层扩大的趋势。可见,北方森林对气候变化响应明显,尽管到目前为止有些响应机制尚不清楚,但变化趋势十分明显。本文旨在为北方森林的经营和管理提供基础数据和技术支持,实现北方森林的可持续经营。      

Interpretation of Climate Change and Agricultural Adaptations by Local Household Farmers: a Case Study at Bin County,Northeast China

Although climate change impacts and agricultural adaptations have been studied extensively, how smallholder farmers perceive climate change and adapt their agricultural activities is poorly understood. Survey-based data (presents farmers' personal perceptions and adaptations to climate change) associated with external biophysical-socioeconomic data (presents real-world climate change) were used to develop a farmer-centered framework to explore climate change impacts and agricultural adaptations at a local level. A case study at Bin County (1980s–2010s), Northeast China, suggested that increased annual average temperature (0.6°C per decade) and decreased annual precipitation (46 mm per decade, both from meteorological datasets) were correctly perceived by 76 and 66.9%, respectively, of farmers from the survey, and that a longer growing season was confirmed by 70% of them. These reasonably correct perceptions enabled local farmers to make appropriate adaptations to cope with climate change: Longer season alternative varieties were found for maize and rice, which led to a significant yield increase for both crops. The longer season also affected crop choice: More farmers selected maize instead of soybean, as implicated from survey results by a large increase in the maize growing area. Comparing warming-related factors, we found that precipitation and agricultural disasters were the least likely causes for farmers' agricultural decisions. As a result, crop and variety selection, rather than disaster prevention and infrastructure improvement, was the most common ways for farmers to adapt to the notable warming trend in the study region.     

大同盆地晚更新世以来气候变化

为了更好的了解大同盆地过去气候的变化过程,找出其气候变化规律,预测未来气候变化趋势,更好地指导农业生产。研究通过对沉积剖面地层的观察与样品的测年,运用磁化率和粒度指标,恢复了大同盆地晚更新世以来的气候变化：整体呈现出暖湿—冷干—暖干的气候旋回特征,分为上更新世许家窑组暖湿期、马兰组干冷期及全新世暖干期,并且气候有逐渐干旱化趋势。部分学者对而近些年降水与气温变化的研究以及未来气候趋势的预测,更证实了这一结论的合理性。总之,大同盆地晚更新世以来气候总体呈干旱化趋势,这一结论将为本区干旱化农业发展政策的制定提供可靠的科学依据。     

气候变化对典型草原区牧草气候生产潜力的影响

20世纪70年代以来,全球的温度变化一直在不断地上升,这给一些草原区的畜牧业带来了严重的阻碍作用。经过对草原区45 a的气候的分析和牧草量的多少,找出了现代气候对畜牧业生产的影响。实践证明草原气候的暖干化比较明显,温度也在增加、降水量在不断减少。影响着畜牧业发展的主要因素是降水量的大小,以降水量、温度对牧场气候生产建立一个实验,对温度和降水进行综合分析温度降低降水量增加时,牧草气候的生产潜力就会增加。     

Atmospheric carbon injection linked to end-Triassic mass extinction

The end-Triassic mass extinction (~201.4 million years ago), marked by terrestrial ecosystem turnover and up to ~50% loss in marine biodiversity, has been attributed to intensified volcanic activity during the break-up of Pangaea. Here, we present compound-specific carbon-isotope data of long-chain n-alkanes derived from waxes of land plants, showing a ~8.5 per mil negative excursion, coincident with the extinction interval. These data indicate strong carbon-13 depletion of the end-Triassic atmosphere, within only 10,000 to 20,000 years. The magnitude and rate of this carbon-cycle disruption can be explained by the injection of at least ~12 × 10(3) gigatons of isotopically depleted carbon as methane into the atmosphere. Concurrent vegetation changes reflect strong warming and an enhanced hydrological cycle. Hence, end-Triassic events are robustly linked to methane-derived massive carbon release and associated climate change.     

The role of carbon dioxide during the onset of Antarctic glaciation

Earth's modern climate, characterized by polar ice sheets and large equator-to-pole temperature gradients, is rooted in environmental changes that promoted Antarctic glaciation ~33.7 million years ago. Onset of Antarctic glaciation reflects a critical tipping point for Earth's climate and provides a framework for investigating the role of atmospheric carbon dioxide (CO(2)) during major climatic change. Previously published records of alkenone-based CO(2) from high- and low-latitude ocean localities suggested that CO(2) increased during glaciation, in contradiction to theory. Here, we further investigate alkenone records and demonstrate that Antarctic and subantarctic data overestimate atmospheric CO(2) levels, biasing long-term trends. Our results show that CO(2) declined before and during Antarctic glaciation and support a substantial CO(2) decrease as the primary agent forcing Antarctic glaciation, consistent with model-derived CO(2) thresholds.     

Do farmers care about climate change? Evidence from five major grain producing areas of China

Using a logistic model, this paper empirically investigated farmers' perception of climate change and its determinants based on a field survey of 1 350 rural households across five major grain producing provinces in China. The results show: i) There is an apparent difference in perception levels for long-term temperature and precipitation changes. Specifically, 57.4% of farmers perceived the long-term temperature change correctly, but only 29.7% of farmers perceived the long-term precipitation change correctly; ii) The factors influencing the farmers' perceptions are almost completely different between precipitation and temperature, the former are mostly agriculture related, while latter are mostly non-agriculture related, except for farm size; and iii) Farmers are not expected to pay more attention to long-term precipitation changes over the crop growing seasons, because less than 30% of farmers can correctly perceive long-term precipitation change. Therefore, to improve the accuracy of farmers' perceptions of climate change, the government is recommended to: i) enhance education and training programs; ii) speed up land transfer and expand household land farm size; iii) develop farmer cooperative organizations; iv) invest more in agricultural infrastructure, specifically in major grain producing regions; and v) improve the agricultural environment and increase farming income.     

近26年来南昌市气候变化特征

根据南昌市1983～2008年的气温、降水、日照时间、相对湿度等气候资料,采用相关性分析、线性回归分析、趋势分析等方法,研究了南昌市近26年来的气候变化特征。结果表明,26年来,南昌市气候变化的主要特征为气温急速上升、湿度急速下降。南昌市年均气温以0.54℃/10a的速率上升,达到极显著水平(P<0.000 1),多年平均气温为18.01℃,四季平均气温均呈上升的趋势,春秋季增温最明显,气候倾向率分别为0.89(P<0.000 1)、0.66℃/10a(P<0.000 1);年降水量以16.12 mm/10a的速率上升,多年平均降水量为1610.6 mm;年日照时间以42.26 h/10a的速率上升,春季日照时间显著上升(43.30 h/10a,P<0.01);年均相对湿度以-9.96%/10a的速率极显著下降(P<0.000 1),四季平均相对湿度倾向率分别为-10.00(P<0.005)、-11.59(P<0.000 1)、-9.67(P<0.005)、-8.57%/10a(P<0.05)。     

砂砾粒径对砂田西瓜根际温度的效应

以不覆砂露地（CK）为对照,通过铺设砂石粒径为1~3 mm的毛砂、10~20 mm豆砂、80~120 mm扁平椭圆卵石和1~100 mm当地砂田普通混砂,研究不同粒径砂砾覆盖对砂田西瓜根际温度的效应,监测砂田0~25 cm不同深度土壤温度变化。结果表明,砂田早春0~25 cm土壤日均温度比对照高0.3~3.0℃,日最高温度随土层深度的增加而逐渐降低,各层土壤最高温度出现时间比对照滞后0.5~2.5 h。毛砂、豆砂、卵石和混砂覆盖下砂层5 cm处根际平均温度分别比对照增加了20.03%、20.66%、0.47%、8.48%,除卵石外,早春其余粒径砂砾覆盖的砂田砂下5 cm处根际温度显著高于对照;砂层下5 cm处土壤温度受外界环境的影响最大,其变化规律可用一元三次函数y=ax3＋bx2＋cx＋d拟合,各处理拟合相关性系数均在0.87以上,其它土层曲线变化规律不明显。不同粒径的砂砾覆盖0~25 cm土壤温度增加效应从高到低顺序为豆砂、毛砂、混砂、卵石,其增加幅度随土壤深度的增加而减缓,豆砂和毛砂增温较慢,但增加幅度较大,卵石增温散温都快但增加量小。覆砂后0~25 cm根际最高温度毛砂、豆砂、卵石和混砂分别比对照增加了2.52、2.00、0.64、1.04℃,但不同深度土壤温度变化规律无明显差异。     

山东省棉花温度适宜度变化趋势

选取山东省近49年(1960～2008)19个站点逐旬、逐月气温资料,结合前人的研究构建了棉花的温度适宜度模型,并计算各站点的温度适宜度变化。结果表明:山东省棉花的温度适宜度总体呈现增加趋势,不同地区温度适宜度变化速度有地域差异,并对变化的原因进行了初步分析;建议未来适当扩大棉花种植面积,以应对气候变化。