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Climate change affects relationships between regions. The sequence of peacemaking events between farming and nomadic groups in northern China from the Western Han to the Qing dynasty was constructed based on historical documents. We analyzed the impacts of climate change on ethnic relationships using war and temperature sequence data from previous studies. The main results are as follows: 1) There were 504 peacemaking events between farming and nomadic groups, with an average frequency of 2.4 times per decade. Paying tribute (68.9%) occurred significantly more frequently than intermarriage for pacification (31.1%). The sequences showed different stages. 2) There were more peacemaking events during cold periods and fewer during warm periods. Intermarriage for pacification played a greater role in peacemaking during warm periods, while paying tribute was more important during cold periods. 3) High-incidence stages of war and of peacemaking events alternated. Peacemaking events occurred more frequently during cold periods and wars occurred more frequently during warm periods. 4) During warm periods, farming and nomadic groups had enough power to contend with each other, wars occurred frequently, and intermarriage was often used for peacemaking. During cold periods, agriculture and animal husbandry declined, both sides weakened, and the power difference between them usually increased. Wars rarely occurred, and paying tribute was often used for peacemaking. Ethnic relationships are affected by many factors. As a background factor influencing land productivity, climate indirectly affected conflict-resolution measures between farming and nomadic groups. We can hereby consider ways to manage interregional ethnic relationships under global climate change today.

To improve the accuracy of historical cropland data, we reconstructed cropland cover in the northern China’s farming–pastoral zone during the Liao dynasty using historical literature and settlement relics. We first reconstructed the total cropland area using historical household data based on the cropland area per household. Next, we allocated the cropland area into 5′ grid cells weighted by settlement density to generate a cropland data. Our main findings were as follows: (1) Data on settlement relics enabled not only the identification of ancient farming areas but also the allocation of cropland cover within high resolution grids in the study area. (2) In the flourishing period of the Liao dynasty, the total cropland area was 0.39 × 104 km2. The cropland grids comprised 28.30% of the total grids, with average and maximum values of cropland fractions of 6.61% and 31.18%, respectively. (3) Compared with our result, we found that the PJ overestimate the cropland area of the study area in 1100 AD, whereas the HYDE 3.2 underestimate it. The area of anthropogenic land use in KK 10 was larger than the cropland area in this study too. None of the three global datasets revealed the mosaic spatial distribution pattern of cropland cover in this study area. (4) The orders of land suitability for cultivation during the Liao dynasty and the present period were almost the identical, even in the farming–pastoral zone of northern China, which has fragile ecological environment.

Land use-induced land cover change (LUCC) is an important anthropogenic driving force of global change that has influenced, and is still influencing, many aspects of regional and global environments. Accurate historical global land use/cover datasets are essential for a better understanding of the impacts of LUCC on global change. However, there are not only evident inconsistencies in current historical global land use/cover datasets, but inaccuracies in the data in these global dataset revealed by historical record-based reconstructed regional data throughout the world. A focus in historical LUCC and global change research relates to how the accuracy of historical global land cover datasets can be improved. A methodology for assessing the credibility of existing historical global land cover datasets that addresses temporal as well as spatial changes in the amount and distribution of land cover is therefore needed. Theoretically, the credibility of a global land cover dataset could be assessed by comparing similarities or differences in the data according to actual land cover data (the “true value”). However, it is extremely difficult to obtain historical evidence for assessing the credibility of historical global land cover datasets, which cannot be verified through field sampling like contemporary global land cover datasets. We proposed a methodological framework for assessing the credibility of global land cover datasets. Considering the types and characteristics of the available evidence used for assessments, we outlined four methodological approaches: (1) accuracy assessment based on regional quantitative reconstructed land cover data, (2) rationality assessment based on regional historical facts, (3) rationality assessment based on expertise, and (4) likelihood assessment based on the consistency of multiple datasets. These methods were illustrated through five case studies of credibility assessments of historical cropland cover data. This framework can also be applied in assessments of other land cover types, such as forest and grassland.

The North China Famine of 1876&ndash, 1879, known in Chinese as the Dingwu qihuang (丁戊奇荒), is a famous case of drought-induced famine in Chinese history. The purpose of this paper is to provide empirical and historical evidence for understanding the impacts of extreme climate events and major disasters and the mechanisms of adaptation. From the aspects of famine-related migration and the allocation of relief money and grain, the regional interactions in social responses to extreme climate events were analyzed. This paper collected 186 records from historical documents. Regarding the regions as the nodes and the relationships between regions as the links, the spatial patterns of famine-related migration and the allocation of money and grain from 1877 to 1878 were rebuilt. The results show that, firstly, famine-related migration appeared to be spontaneous and short-distanced, with the flow mainly spreading to the surrounding areas and towns. Secondly, as a state administrative action, the relief money and grain from the non-disaster areas were distributed to the disaster areas. However, the distribution of relief grain affected the equilibrium of the food market in non-disaster areas, which led to fluctuations in food prices.

Modern global cropland products have been widely used to assess the impact of land use and cover change (LUCC) on carbon budgets, climate change, terrestrial ecosystems, etc. However, each product has its own uncertainty, and inconsistencies exist among different products. Understanding the reliability of these datasets is essential for knowing the uncertainties that exist in the study of global change impact forced by cropland reclamation. In this paper, we propose a set of coincidence assessments to identify where reliable cropland distribution is by overlaying ten widely used global land cover/cropland datasets around 2000 AD. A quantitative assessment for different spatial units is also performed. We further discuss the spatial distribution characteristics of different coincidence degrees and explain the reasons. The results show that the high-coincidence proportion is only 40.5% around the world, and the moderate-coincidence and low-coincidence proportion is 18.4% and 41.1%, respectively. The coincidence degrees among different continents and countries have large discrepancies. The coincidence is relatively higher in Europe, South Asia and North America, while it is very poor in Latin America and Africa. The spatial distribution of high and moderate coincidence roughly corresponds to the regions with suitable agricultural conditions and intensive reclamation. In addition to the random factors such as the product&rsquo, s quality and the year it represented, the low coincidence is mainly caused by the inconsistent land cover classification systems and the recognition capability of cropland pixels with low fractions in different products.

Relic archeological settlement is used to indicate the development of agriculture. We extracted 8865 relic archeological settlements from theAtlas of Chinese Cultural Relicsto analyze how the spatiotemporal distribution of archaeological settlements was influenced by temperature changes and social factors during the last millennium. During the Liao dynasty (AD 916–1125) and Jin dynasty (AD 1115–1234) in the Medieval Warm Period (MWP), a large number of settlements indicated the development of agriculture as far north as 47°N. The warm climate of the MWP provided sufficient heat resources to promote the implication of positive policies of the Liao and Jin dynasties to develop agriculture and settlements. By contrast, during the dynasties of Yuan (AD 1279–1368), Ming (AD 1368–1644), and Qing (AD 1644–1911) in the Little Ice Age (LIA), the number of settlements declined drastically, and the northern boundary of the settlement distribution retreated by 3–4 degrees of latitude to modern Liaoning Province. Although the southward retreat of the settlements and related agriculture occurred in the cold climate of the LIA, it could not be completely explained by the drop in temperature. Social factors including nomadic customs, ethnic policies, and postal road systems played more important roles to the northern boundaries of the settlement distributions during the Yuan, Ming, and Qing dynasties.

The study on the relationship of abandoned settlements and climate change in the oases could provide a historical reference for understanding human responses to present and future global warming in the arid zone. A total of 554 abandoned historical settlements in Xinjiang Uygur Autonomous Region, China, were used to examine the relationship between abandoned settlements and temperature change over the past 2000 years. The analysis covered dynastic epochs from the Han Dynasty (206BC–220AD) to the Qing Dynasty (1644AD–1911AD) in the oases of Xinjiang. Greater density of settlements was found at the oases larger than 2000 km2, which were more stable and less sensitive to climate change compared to smaller oases. Settlements flourished at small oases and the middle and lower reaches of rivers during warm periods and shrank back to piedmont basins and upstream alluvial fans during cold periods. These results demonstrated responses of oasis agriculture to climate change.

In ancient China, shifts in regional productivity of agriculture and animal husbandry, caused by climate change, either led to wars or peaceful relations between nomadic and farming groups. During the period spanning the Western Han Dynasty to the Tang Dynasty, 367 wars were waged between these groups. While 69 % of the wars were initiated by nomads, 62.4 % were won by the farming groups. On a centennial timescale, the battlegrounds were mostly in northern areas (at an average latitude of 38.92° N) during warm periods, moving southward (at an average latitude of 34.66° N) during cold periods. On a decadal timescale, warm climates corresponded to a high incidence of wars (a correlation coefficient of 0.293). While farming groups were inclined to initiate wars during dry and cold periods, their chances of achieving victory were reduced at such times. The main reasons for this are, first, that a warm climate provided a solid material foundation for nomadic and farming groups, contributing especially to enhanced productivity among the former. However, the overriding desire of nomadic groups to expand essential subsistence means led to wars. Second, during cold periods, farming groups moved to and settled in the south, while nomadic groups occupied the Central Plain. Thus, the locations of the battlefields also changed. While other factors also influenced these wars, climate change served as a backdrop, playing an indirect role in wars between these groups.

To better understand the process of land reclamation in the Dongting Plain (DTP), this paper reconstructed the spatiotemporal distribution of polders in the area. The images of polder patches were extracted from Google Earth using visual interpretation, and the corresponding polder names and times of polder construction were extracted from maps and local gazetteers. Moreover, this paper examined the possible relationships between the spatiotemporal distribution of polders and the regional environment change and socio-economic history. The results showed that: (1) The total area occupied by modern polders (in the 2010s) is 9703.18 km2, and the area was constructed in six stages that constituted 5.73% of the modern total area in 1368–1644, 8.29% in 1644–1735, 9.33% in 1736–1850, 31.71% in 1851–1911, 18.51% in 1912–1949, and 26.41% in 1949–1980. (2) In terms of the spatial distribution of polders constructed at each stage, the polders in 1368–1644 were predominately located in the northern DTP, and polders in 1644–1735 and 1736–1850 were predominately located in the south. Owing to the formation of the Ouchi River and the Songzi River, the new polders were constructed along the rivers in the central plain in the last three stages after 1850. (3) Multi-factors played distinctive roles in the construction of polders in different stages. The location affected the initial spatial distribution of polders in the mid-14th century. In the long run, the growth in population contributed to the increase of polders. The Four Rivers mainly affected the spatial distribution of polders in the south part of the DTP before 1850, and the four channels of the Yangtze River mainly affected polders in the north-central part of the DTP after 1850. The polders along the Xiang and Zi Rivers were cumulatively constructed and formed in multiple stages. The polders were constructed in the period from 1368 to 1850, and area accounted for 57.82% of polders along rivers. The polders along the four channels of the Yangtze River were a gradual development with continuous expansion, and the polder area in 1850–1980 was 92.40%.

The increase in efficiency per surface area of solar cells in recent years, coupled with the continuous miniaturization of electric propulsion systems, have made propulsive capability a highly viable option for small satellites. These propulsion systems enable small satellites to perform orbital maneuvers, to the point where CubeSat-class satellites have been suggested for missions past the lunar orbit. However, applications of these miniature electric propulsion systems on small satellites pose a new challenge for satellite designs, where the appropriate distancing of the thrusters from solar panels cannot be accomplished within the limited volumetric constraints of small satellites. Accordingly, the degradation effects of the exhaust plume on the solar panels may have an undetermined impact on the small satellites. In addition, these new generation miniature electric propulsion systems often use an unconventional propellant that produces unconventional plasma within their plumes. One example is a pulse plasma thruster using metal propellant that results in a metallic plasma plume. Solar cell performance degradation due to radiation and ultraviolet light has been thoroughly studied in the past. Gaseous-plasma effects also have been studied, but there is a lack of data on how a metallic plasma plume will affect solar cells mainly because it is non-conventional plasma that is not frequently used in space applications. The main goal of this research is to characterize the degradation and coating effects of metallic plasma plume on solar cells. In particular, this study will focus on the Micro-Cathode Arc Thruster developed at The George Washington University. It is a compact propulsion system designed for small satellites and has been previously flown on a CubeSat. This paper will examine the theoretical issues, and characterize solar cell performance degradation resulting from deposition of the metallic exhaust plasma plume on the surface of the cover glass.1

The impact of climate change on agricultural production is integral to understanding the impacts of historical climate change on society and the economy, which could provide historical references for dealing with current and future global climate change. Continuous proxy series of human activity that extend to more than 1000 years in the past are few, especially for high-resolution series. There was a lack of quantitative records of grain harvest in Chinese history except during the Qing Dynasty. Thus, it is difficult to reconstruct long-term and high-resolution agricultural production series. In this paper, the method developed by Su et al. (2014) is used to reconstruct the grain grade sequence with a 10-year resolution from 210 BC to 1910 AD in China, and the changes between temperature and grain yield grades are compared. A positive correlation between the winter half-year temperature departure and the grain yield from 210 BC to 1910 AD in China was found. The change of grain yield grades could be divided into five stages. The bumper harvest stages corresponded to the warm periods, and poor harvest stages corresponded to the cold periods. In both warm and cold periods, the grain yield grades assumed a trend of convergence with the temperature increase. The sensitivity of grain yield to temperature change became weakened over time from 210 BC to 1910 AD, perhaps due to the strengthened adaptive capacity of agriculture to temperature change, with the extension of farming to southern China, progress of farming technology, and introduction of high-yielding crop varieties. Remote linkages between the agricultural change in China and the human civilization in Europe were found, implying the impacts of temperature change are globally synchronous.

Cropland area per capita and pressure index on cropland are important parameters for measuring the social vulnerability and sustainability from the perspective of food security in a certain region in China during the historical periods. This study reconstructed the change in spatial distribution of cropland area per labor/household and pressure index on cropland during the 17th–20th century by using historical documents, regression analysis, pressure index model, and GIS (geographic information system). Following this, we analyzed the impacting process of climate change and sustainability of cropland use during the different periods. The conclusions of this study are as follows: (i) there was an obvious spatial difference of labor/household density, as there was higher density in three agricultural areas, which had the same pattern as cropland distribution during the same periods; (ii) Cropland area per capita was relatively higher during the 17th–18th century, which were above 0.4 ha/person in the majority of counties and were distributed homogenously. Until the 19th century and the beginning of 20th century, cropland area per capita in a considerable proportion of regions decreased below 0.2 ha/person, which embodies the increase in social vulnerability and unsustainability at that time; (iii) The pressure index on cropland also showed a spatial pattern similar to cropland area per capita, which presented as having a lower threshold than nowadays. During the 17th–18th century, there was no pressure on cropland. In comparison, in the 19th century and at the beginning of 20th century, two high-value centers of pressure index on cropland appeared in the Middle Shandong and the Jiaodong region. As a result, pressure on cropland use increased and a food crisis was likely to have been created; (iv) A higher extent of sustainable cropland use corresponded to the cold period, while a lower extent of sustainable cropland use corresponded to the warm period in Shandong over the past 300 years. The turning point of the 1680s from dry to wet was not distinctively attributed to the decrease in the extent of sustainable cropland use in Shandong. Since the beginning of the 20th century, the increasing pressure on the sustainability of cropland use finally intensified the social conflict and increased the probability of social revolts.

The occurrence of bumper or poor grain harvests in ancient China plays an important role in explaining how past climate changes affected the economy. Because of the lack of long-term continuous and high-resolution quantitative data for reconstructing the series of grain harvests in ancient China, understanding of the impacts and mechanisms involved in climate change is limited. This study presents a method designed for reconstructing grain harvest series by quantifying grain output levels based on the descriptions in historical documents. The method involves setting the grain output level for each year based on very specific meanings of different words, calculating a yield index based on the structure of each level and assessing grain yields (bumper or poor harvests) every 10 years. First, 1636 records related to grain yields (including crop yields, food security, agricultural disasters, grain prices, grain storage and people’s livelihoods) for each year were retrieved from history books called the Twenty-Four Histories. Second, using this method, a 10-year resolution graded grain harvest series from the Western Han Dynasty to the Five Dynasties (206 BC–960 AD) is reconstructed. Finally, the relationship between the variations in temperature and precipitation and the fluctuation of grain yields is examined. The results show that from the Western Han Dynasty to the Five Dynasties, bumper, average and poor harvest decades accounted for 33.3%, 39.3% and 27.4% of the 1,166-year period, respectively. The grain yields during 206 BC–960 AD can be divided into three stages: a period of bumper harvests during 206–51 BC, poor harvests during 50 BC–590 AD and bumper harvests during 591–960 AD. Bumper harvest decades typically experienced a warm climate with normal or high levels of precipitation, while poor harvest decades had a cold and dry climate. A positive correlation was found between temperature and grain yield because a warm climate allows a full use of resources. The observed relationship between precipitation and grain yield indicated that both flooding and droughts cause poor harvests, which confirms that agricultural production in the monsoon climate of eastern China is greatly impacted by conditions of limited heat and extreme precipitation.

Using land reclamation information from gazetteers and corresponding historical records as further evidence, we extracted information about land reclamation in the early years of reclamation (at the “beginning date”) and during the climax period (the maximum extent). We analyzed land reclamation processes in the farming–grazing transitional zone in northeast China during the Qing Dynasty (1644–1911). Among thirty-seven counties for which the beginning date of land reclamation was recorded, 32 percent began reclamation early, primarily between the Shunzhi (1644–1661) and the Kangxi reigns (1662–1722), 19 percent were exploited during the Yongzheng reign (1723–1735), and 19 percent were exploited during the Guangxu reign (1875–1908). Among forty-six counties for which the maximum extent of land reclamation was recorded, the counties of Fengning, Longhua, and Longjiang were extensively exploited before 1800. From 1800 to 1860, four counties were extensively exploited, including Changtu County, Horqin Left Wi...

Climate change affected the agricultural expansion and the formation of farming-grazing transitional patterns during historical periods. This study analyzed the possible range of the boundary shift of the potential suitable agriculture area in the farming-grazing transitional zone in the northeastern China during the 20th century. Based on modern weather data, 1 km-resolution land cover data, historical climatic time series, and estimation by using similar historical climatic scenes, the following was concluded: 1) The climate conditions of suitable agriculture areas in the farming-grazing transitional zone in the northeastern China between 1971 and 2000 required an average annual temperature above 1°C or ≥ 0°C accumulated temperature above 2500°C–2700°C, and annual precipitation above 350 mm. 2) The northern boundary of the potential suitable agriculture area during the relatively warmer period of 1890–1910 was approximately located at the position of the 1961–2000 area. The northern boundary shifted back to the south by 75 km on average during the colder period of the earlier 20th century, whereas during the modern warm period of the 1990s, the area shifted north by 100 km on average. 3) The western and eastern boundaries of the suitable agriculture area during the heaviest drought periods between 1920s and 1930s had shifted northeast by 250 km and 125 km, respectively, contrasting to the boundaries of 1951–2008. For the wettest period, that is, the 1890s to the 1910s, the shift of western and eastern boundaries was to the southwest by 125 km and 200 km, respectively, compared with that in the 1951–2008 period. This study serves as a reference for identifying a climatically sensitive area and planning future land use and agricultural production in the study area.

How the past human society responded to climatic disasters could provide better understanding on the nature of climate–human–ecosystem interactions and the knowledge of the vulnerability for the society in the context of changing climate. In this paper, the North China Plain in the Qing dynasty (1644–1911) is selected as a typical regional social-ecological system; with historical information kept in official documents, social responsive behavior and measures to flood/drought (e.g., reclamation, disaster relief, migration, revolt) are quantitatively described with proxy indicator time-series. It is found that the dominant responsive strategy altered significantly in different stages: (1) stage of cropland expansion (1644–1720); (2) stage of governmental disaster relief (1721–1780); (3) stage of increasing climate refugees (1781–1860); (4) stage of revolt and emigration (1861–1911). The multi-stage evolution of social response was impacted by various natural and social factors: (1) regional population–food balance and governmental finance were the most important limiting factors; (2) the interaction between the governmental policy and refugees’ behavior in disasters affected the social consequences to a certain extent; (3) decadal-to-multi-decadal climate change would also impact the social response measures, even directly trigger the shift of dominant responsive strategy. This study would be helpful for deeper understanding of social resilience and better responding to climate change and extreme events in the present and future.

In the present study, Eastern Inner Mongolia (EIM) and the North China Plain (NCP) during the Qing Dynasty (1644-1911) were selected as study areas. Based on records of agricultural exploitation, settlement expansion, and revolts obtained from the Veritable Records of the Qing Dynasty (a collection of official records), a collection of proxy data reflecting historical social change in EIM was gathered. The social response in EIM to the immigrants from the NCP, who were mainly destitute and homeless refugees and came into EIM under the acquiescence or even with the encouragement of the government in and after a severe flood or drought, was analysed by comparing the data on climatic factors as well as changes in governmental policy. The results indicated that social response was significantly dependent on phase changes. In the 18th century, immigrants from the NCP promoted the reclamation of EIM, which was a pastoral region throughout the 17th century and displayed agricultural prosperity, settlement expansion, and positive regional interactions. However, from the beginning of the 19th century, agriculture declined and settlement slowed. Immigrants intensified local social contradictions in EIM, which led to a series of armed revolts and collapse in the late 19th century. This transformation was affected by both natural and human factors, especially periodic fluctuations in temperature, which significantly affected land use and environmental capacity in EIM by controlling the location of the agro-pastoral transitional zone, and the implementation and repeal of quarantine policy, which immediately affected the extent of immigration in EIM. (c) 2012 Elsevier Ltd. All rights reserved.

Land cover changes induced by historical cultivation in ecologically fragile areas involving important issues such as environmental change, ecology, and human sustainability are particularly worthy of attention. This paper reconstructs the spatial distribution of cultivated areas at the county level in the eastern farming-pastoral ecotone of northern China for four time periods during the twentieth century. The paper also analyzes how the location of cultivation ratio contours of 15 and 30 %, representing the boundaries of agricultural areas, have moved and the formation process of farming-pastoral ecotone patterns during this period. The study concludes that the area and ratio of cultivated land fluctuations increased during the twentieth century. The boundaries of the cultivation ratio contours of 15 and 30 % continually moved west and north. Moving north took priority over the other directions during the period of 1916–1940, when its center moved the farthest during the twentieth century, and the boundaries primarily moved westward during 1940–1980 and northwestward during 1980–2000. The distance, direction, and extent of the movement of the cultivation boundaries are all related to agricultural area expansion processes during this period, finally resulting in the creation of the modern farming-pastoral ecotone pattern.

Climatic disaster-induced migration and its effects on land exploitation of new settlements is a crucial topic that needs to be researched to better understand the impact of climate change and human adaptation. This paper focuses on the process and mechanism of migrant–reclamation in Northeast China in response to climatic disasters over the past 300 years. The research used comparative analysis of key interlinked factors in this response involving drought/flood events, population, cropland area, farmer revolts, administrations establishment, and land reclamation policies. It draws the following conclusions: (1) seven peaks of migrants–reclamation in Northeast China were evident, most likely when frequent climatic disasters happened in North China, such as the drought–flood in 1851–1859, drought in 1875–1877, and drought 1927–1929; (2) six instances of policy transformation adopted to cope with extreme climatic events, including distinctive examples like changing to a firm policy prohibiting migration in 1740 and a subsequent lifting of that prohibition in 1860; and (3) the fast expansion of the northern agricultural boundary since the middle of the nineteenth century in this area benefited from a climate change trend from a cold period into a warm period. Altogether, over the past 300 years, extreme climatic disasters in North China have deepened the contradiction between the limited land resources and the rapidly increasing population and have resulted in migration and reclamation in Northeast China. Climate, policy, and reclamation constructed an organic chain of response that dominated the land use/cover change process of Northeast China.

International trade is an important impact factor to the carbon emissions of a country. As the rapid development of Chinese foreign trade since its entry into the WTO in 2002, the effects of international trade on carbon emissions of China are more and more significant. Using the recent available input-output tables of China and energy consumption data, this study estimated the effects of Chinese foreign trade on carbon emissions and the changes of the effects by analyzing the emissions embodied in trade between 2002 and 2007. The results showed a more and more significant exporting behavior of embodied carbon emissions in Chinese international trade. From 2002 to 2007, the proportion of net exported emissions and domestic exported emissions in domestic emissions increased from 18.32% to 29.79% and from 23.97% to 34.76%, respectively. In addition, about 22.10% and 32.29% of the total imported emissions were generated in processing trade in 2002 and 2007, respectively, which were imported and later exported emissions. Although, most of the sectors showed a growth trend in imported and exported emissions, sectors of electrical machinery and communication electronic equipment, chemical industry, and textile were still the biggest emission exporters, the net exported emissions of which were also the largest. For China and other developing countries, technology improvement may be the most favorable and acceptable ways to reduce carbon emissions at present stage. In the future negotiations on emissions reduction, it would be more fair and reasonable to include the carbon emissions embodied in international trade when accounting the total emissions of an economy.

Historical cropland datasets are fundamental for quantifying the effects of human land use activities on climatic change and the carbon cycle. Two representative global land-use datasets, the Global Land Use Database (termed SAGE dataset) and the Historical Database of the Global Environment (termed HYDE dataset) have been established and used widely. Despite improvement of data quality and methodologies for extracting historical land use information, certain dataset limitations exist that need to be quantified and communicated to users so that they can make informed decisions on whether and how these land-use products should be used. The Cropland data of Northeast China (CNEC) is based on calibrated historical data and a multi-sourced data conversion model, and reconstructs cropland cover change in Northeast China over the last 300 years. Using the CNEC as a reference, we evaluated the accuracy of cropland cover for SAGE and HYDE in Northeast China at spatial scales ranging from the entire Northeast China to provinces and even individual raster grid cells. Neither SAGE nor HYDE reflects real historical land reclamation. Cropland areas in SAGE are overestimated by 20.98 times in 1700 to 1.6 times in 1990. Although HYDE is better, there are significant disagreements in cropland area and distribution between HYDE and CNEC, especially in the 18th and 19th centuries. The proportion of total grid cells whose relative error was greater than 100% was 63.55% in 1700 and 53.27% in 1780. Global cropland dataset errors over Northeast China originate mainly from both the reverse calculation method for historical cropland data based on modern spatial patterns, and modern land-use outputs from satellite data.

Land use/cover change induced by human activities has emerged as a “global” phenomenon with Earth system consequences. Northeast China is an area where the largest land cultivation activities by migrants have happened in China during the past 300 years. In this paper, methods including documentary data calibration and multi-sourced data conversion model are used to reconstruct historical cropland cover change in Northeast China during the past 300 years. It is concluded that human beings have remarkably changed the natural landscape of the region by land cultivation in the past 300 years. Cropland area has increased almost exponentially during the past 300 years, especially during the past 100 years when the ratio of cropland cover changed from 10% to 20%. Until the middle of the 19th century, the agricultural area was still mainly restricted in Liaoning Province. From the late 19th century to the early 20th century, dramatic changes took place when the northern boundary of cultivation had extended to the middle of Heilongjiang Province. During the 20th century, three agricultural regions with high ratio of cropland cover were formed after the two phases of spatial expansion of cropland area in 1900s–1930s and 1950s–1980s. Since 1930s–1940s, the expansion of new cultivated area have invaded the forest lands especially in Jilin and Heilongjiang Provinces.

Impacts of climate warming on heating energy consumption and southern boundaries of severe cold and cold regions of China in the past 20 years are analyzed by using daily and monthly average temperature data from 590 weather stations in China and based on regulations of Heating Ventilation and Air Conditioning Design Rules (GB50019-2003) and Thermal Design Rules for Civil Building (GB50175-93) (China National Standard). The contribution of climate warming to coal saving for heating during cold seasons in major cities is calculated according to indices of coal consumption for heating in major cities during cold seasons defined in Energy Conservation Design Standard for New Heating Residential Buildings (JCJ26-95). Comparing with the period before 1980, southern boundaries of severe cold and cold regions shift toward north up to 2 degrees in latitude since the mid-1980s. Theoretically, climate warming could contribute to 5%–10% coal savings for heating since the mid-1980s in major cities, and even more since the mid-1990s.

To advance global change rssearch, it is essential to reconstruct changes in historical cropland coverage on a regional scale in China. This paper presents data collected from 244 local gazetteers, government statistical records and remote-sensing land cover data from the Shandong Province. The study reconstructed the spatial distribution of the rate of reclaimed land at the county level and compared this map with a map of the current spatial distribution of suitable cropland. The following conclusions were drawn: (i) The rate of cultivated land grew exponentially. The extent of reconstruction in cropland areas during the 17th century, 18th~19th centuries, the beginning of the 20th century, the 1980 s and the beginning of the 20th century are 4.51 mha, 6.51 mha, 7.52 mha, 8.53 mha and 11.80–12.00 mha, respectively. (ii) Several agricultural centers formed during the late 17th century. Until the beginning of the 20th century, the reclamation rate increased rapidly near the four southern lakes, which are located in the Zaozhuang and Linyi regions. (iii) Most reclamation activities before the 19th century occurred in suitable agricultural areas and the cultivated land was already reclaimed by the beginning of the 20th century.

Since 1980s, global environmental change has gradually become the hot research field of earth science and life science. Ecology, as an interdisciplinary of the two sciences, intervenes more global environmental change study. This study concerns the change of support capacity from earth system to life, which obviously accords with ecology’s mission. Recognizing the importance of integral systematic concept and long-term systematic simulating observation on solving the problem of environmental change, international geological and ecological circles changes the organization formation of scientific research and continuously establish many large research projects. The research organization formation and related academic exchange activities had promoted the intercross fusion between different subjects and the meta-synthesis of studies on resource, environment, ecology, and disaster.

An approach to controlling heat flux based on electron emission in the double layer assembly of two materials with different work functions has been developed. It is shown that this two-electrode assembly promotes the inverse heat flux exhibiting a thermal metamaterial property in a wide range of temperatures. The proposed thermal metamaterial can be used as an active element of a thermal diode, ensuring heat flux in one direction regardless of temperature difference.

Background The process of human response to natural disasters and its mechanisms as revealed by historical events still has a broad significance for modern society. This study analyzed the disaster relief process and the social response for two floods in China: the Yongding River flood in 1801 and the Yellow River flood in 1841. These two floods reflect the different response processes between the national and provincial capitals during a stage of climate cooling and social transition in the Qing dynasty. Results Applying methods of historical documents analysis and qualitatively comparative analysis to the materials such as Relief Chronicles Authorized by the Emperor in XinYou and Flood Description in Bian Liang, it shows that: (1) In 1801, the central government took on a lead position, from flood surveying to relief processes. However, local government and gentries played an important role in 1841. (2) In 1801, the government successfully undertook a series of relief measures addressing production, housing, food prices, taxes, and water conservancy and administration. In 1841, the response measures were relatively simple, focusing mainly on providing shelter and food for victims. (3) The government carried out long-term disaster prevention measures such as dredging channels after the flood in 1801. In 1841, however, the efforts were focused mainly on emergency rescue. (4) Refugees in the 1801 flood were effectively managed by a centralized authority. In 1841, regulation of the flooding was delayed by corruption and conflicts between officers, leading to an expansion of the disaster’s impact. Conclusions Above results have led to the conclusion that disaster relief systems and response measures had a significant effect on the consequences of those floods. Various flood relief measures and natural disasters management regimes have implications for contemporary flood hazard mitigation.