Abstract Background: Carbon emissions have received increasing international attention in recent years and countries have undertaken different measures to control emissions. Research into carbon emissions has also increased year by year, but remains mainly focused on national total carbon emissions, and per-capita carbon emissions have received less attention. This paper investigates spatial and temporal changes in per-capita carbon emissions and uses the Mann-Kendall test to assess the directions and magnitudes of trends, and to investigate abrupt changes in per-capita carbon emissions. Results: We found the highest positive growth rate in Oman, at 0.439 mts/yr, and the highest negative growth rate in United Arab Emirates, at -0.462 mts/yr. If no further mitigation measures are taken, we estimate that the current emissions trends will persist into the future for 86% of countries. The number of change-points was greatest in 1994 and smallest in 1999. The shift in the center of gravity for per-capita carbon emissions changed direction in 2004. From 1992 to 2004, the gravity center for per-capita carbon emissions gradually shifted to the southwest, and, after 2004, it gradually shifted to the southeast until 2018. Conclusions: Europe has entered the carbon reduction phase, but it is not yet significant, and carbon emissions are still increasing in the rest of the continent. The main driver for the westward shift in the gravity center before 2004 was that carbon emissions grew more strongly in the West than in the East before 2004, while the driver for the eastward shift in the gravity center after 2004 was a combination of emission reductions in the West and emission increases in the East.

In recent years, carbon emissions have become a hot spot issue, and countries have made efforts to control the increasing rate of CO2 concentration. Prior studies have mainly focused on the national total carbon emissions, but per capita carbon emissions are still poorly known. Here, we used multiple economic development indices to investigate the dynamics of per capita carbon emissions. Additionally, we used the Mann–Kendall test to assess the directions and magnitudes of trends and to investigate abrupt changes in per capita carbon emissions. Our results showed the highest positive growth rate of 0.439 mts/yr in Oman, and the highest negative growth rate of −0.462 mts/yr in the United Arab Emirates. Hurst Index analysis showed that about 86% of countries will keep the current trends of carbon emissions if current mitigation measures remain unchanged. Furthermore, we analyzed the shift in the center of gravity for per capita carbon emissions and used the contribution decomposition method to identify the drivers for the shift, which changed direction in 2004. The main driver behind the westward shift in the gravity center before 2004 was the fact that carbon emissions grew more strongly in the west than in the east before 2004, while the driver for behind the eastward shift in the gravity center after 2004 was a combination of emission reductions in the west and emission increases in the east. Our results highlighted the importance of understanding that the per capita CO2 emissions are clearly defined within the context of global carbon neutrality, which can help policymakers set more reasonable targets with which to better achieve carbon neutrality goals.

The landscape index is a quantitative index which reflects characteristics of structure composition and spatial pattern in landscape studies, it is, therefore, expected to describe the spatial pattern of scientific research in bibliometric analysis. In this study, a novel attempt to regard scientific research as a kind of ‘landscape’ was made, and landscape indices were improved for bibliometric analysis to measure the spatial pattern of scientific research. For illustrating the feasibility of our method, global geoscience research from 1994 to 2018 was presented as a case. Moreover, spatiotemporal migration of landscape centroids was visualized. The results indicated that global geoscience publications increased steadily and articles were highly concentrated at the country level. The top 10 countries published 69.93% of total articles and 84.68% of geoscience articles were from top 20 productive countries. The spatial migration of centroids was mainly reflected in the longitude because of significant increasing of articles in eastern countries, especially in China with the growth rate of 747.14%. At the patch scale, the change trend of improved landscape indices verified the spatiotemporal changes of global distribution of geoscience articles. At the landscape scale, the strengthening of global international collaboration is the main driving forces of spatial heterogeneity of global geoscience research. This study is expected to help readers to understand global trends of geoscience research in the past 25 years, and to promote the development of bibliometric analysis towards the directions of spatialization and visualization.

The stationarity of hydrological systems is dead in the era of the Anthropocene. Has our hydrological or water resources knowledge been well transformed to address this change? By using publications indexed in the Web of Science database since 1900, we aim to investigate the global development of water resources knowledge at the river basin scale with a systems approach, of which water resources knowledge development in a river basin is defined as a complex system involving the co-evolutionary dynamics of scientific disciplines and management issues. It is found that (1) legacy-driven water resources knowledge structures have consistently dominated most of the highly researched river basins in the world, while innovation-driven structures are identified in the river basins receiving increasing research publications in the recent period; (2) the management issues addressed by legacy-driven river basin studies are increasingly homogenized, while a wider range of emerging issues are considered by innovation-driven river basin studies; and (3) cross-disciplinary collaborations have remained largely unchanged and collaborations with social sciences have been very limited. It is concluded that the stationarity of water resources knowledge structure persists. A structural shift of water resources knowledge development is urgently needed to cope with the rapidly changing hydrological systems and associated management issues, and opportunities for such a shift exist in those less researched but globally distributed innovation-driven river basins.

Global scientific research output has experienced continuous and rapid growth during the last 20 years. The spatial and temporal variations of the international papers at the national and regional scales were analyzed by combining the remotely sensed nighttime light data from the Defense Meteorological Satellite Program's Operational Linescan System. The findings indicate that the publication of international-circulation scientific papers in most of the countries examined have experienced a trend of exponential increase which can be positively correlated with nighttime light in those counties or regions. Furthermore, the developing countries have higher correlation coefficients than the developed countries. Thus, literal nighttime light data can potentially be used in future to better predict the number of publications of the research of figurative 'luminaries' residing in developing countries.

基于汤森路透(Thomson Reuters)的基本科学指标(ESI)和科学引文索引扩展(SCIE)文献数据统计,分析了近10年主要国家和研究机构在地球科学领域的论文产出及其研究影响力、研究热点方向等,并重点分析了中国在该领域的研究影响力.分析结果表明,在国际地球科学研究领域,美国的论文数量最多,英国和美国的论文影响力较高,日本各方面接近平均水平,俄罗斯有关地球科学研究的论文占其本国科研论文的比例高于其他国家,新兴经济体国家普遍重视地球科学研究,但论文的国际影响力总体还偏弱.中国的地球科学研究近年来发展迅速,相关研究成果及其影响力在新兴经济体国家中表现突出,但在国际合作和高影响力论文产出方面与发达国家相比尚有一定差距.

Cited information is an important pathway of scientific influence. It can reflect the knowledge flows among research units. This study develops two new bibliometric indices—the Citation Flow Index (CFI) and the Normalized Citation Flow Index (NCFI)—to measure knowledge flows based on scientific literature citations. The CFI measures the interactions of knowledge flows among different research units. The NCFI measures the number of papers that a research unit cited and the number of papers by a research unit that are cited. The newly developed indices were tested on a country-wide scale using the literature on the Qinghai-Tibet Plateau (QTP) as an example. The results indicate that the worldwide flow of knowledge on the QTP can be quantitatively measured and spatially displayed. Additionally, the annual NCFI change trend is analyzed for each research unit.

Cited information is an important pathway of scientific influence. It can reflect the knowledge flows among research units. This study develops two new bibliometric indices—the Citation Flow Index (CFI) and the Normalized Citation Flow Index (NCFI)—to measure knowledge flows based on scientific literature citations. The CFI measures the interactions of knowledge flows among different research units. The NCFI measures the number of papers that a research unit cited and the number of papers by a research unit that are cited. The newly developed indices were tested on a country-wide scale using the literature on the Qinghai-Tibet Plateau (QTP) as an example. The results indicate that the worldwide flow of knowledge on the QTP can be quantitatively measured and spatially displayed. Additionally, the annual NCFI change trend is analyzed for each research unit.

Although the research and application of a geographic information system (GIS) in bibliometrics remains in its initial stage, several valuable attempts have been made in recent years. This paper provides our overview regarding this area. We first reviewed the spatial information mining derived from literature, including structured and unstructured data. The spatial display and the basic spatial operations for the geographic information derived from literature were then introduced, demonstrating that GIS can be directly used to construct digital libraries. Some literature database websites have begun to utilize WEBGIS to display the spatial distribution of an author's location. Additionally, the spatial distribution information can be displayed in various modes with other specialized tools. Potential spatial analyses in bibliometrics were then discussed, introducing geostatistical and buffer analyses as case studies. Finally, several bibliometric indicators attached with research units were investigated. When the quantitative research index units are linked with the research spatial position, they can be displayed, queried and retrieved spatially. Future work to advance the application and research of GIS in bibliometrics is still warranted.

The subject intersection becomes one of the hot research topics recently. It is a new direction to integrate the GIS technologies with Bibliometrics. The literatures concerned with geosciences normally involve some spatial related information. In this paper, the spatial information of the study area and sampling or observing points was extracted. Then these data were analyzed and presented by using the GIS technologies. The results indicate that there are big variations of the spatial distribution. For the whole Qinghai-Tibet plateau, the degree of interest increase as follow: southwest, northwest, southeast, and northeast. For the regions, Qilian Mountains, Qiangtang plateau, Qinghai-Tibet Road and Qinghai-Tibet Railway, Qinghai Lake, and Sichuan-Tibet Road are the hotspot regions. There are differences of the distribution characteristics in the different segments along the latitudinal direction and longitudinal direction. There is transfer tendency from middle Qinghai-Tibet Plateau to northern Qinghai-Tibet Plateau. Most of sampling and observing points are close to the traffic lines. The point numbers decrease quickly along with the increasing distance to the traffic lines.

The subject intersection becomes a hot research topic recently. This paper tried to couple the Bibliometrics and Geographical Information System (GIS) technologies for studying on the spatial information mining and visualization from the Qinghai-Tibet Plateau's literature. All the literatures about Qinghai-Tibet Plateau research were indexed in the ISI Web of Knowledge. The statistical tables about the authors were extracted from the papers by using the method of bibliometrics. The spatial information of the author's countries was linked with the GIS database. The spatial distribution was presented by the format of maps based on the GIS technologies. Comparing with the regular presentation forms of the bibliometrical analysis, the spatial distribution maps can afford more abundant and intuitive senses for the users.

The northwest China, typical arid and semi-arid regions, is the first or second-degree sensitivity zones for global change. Monitoring vegetation change is an important method to study the impacts of global climate change. Time-series satellite remote sensing data make it possible to monitor vegetation at different spatial and temporal resolutions globally. A long time series of Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) data with 8x8 km2 spatial resolution and during 1982 to 2003 were used to monitor the vegetation cover in the northwest China. The monitoring results indicate an obvious greening trend exists. The precipitation and relative humidity have high correlations with the SINDVI. So the water condition is the most important factors for the spatial distribution of the SINDVI levels. The precipitation and temperature are the primary driving factors for inter-annual vegetation changes.

The urban population density declines from Central Business District (CBD) to city edge. Some studies have explored several mathematical forms to describe the relationship between population density and location. But these models assume that the city is single center and the urban population decline with concentric circle format. It is difficult to satisfy this requirement in actual cities. A distance variable, city edge distance, has been developed to solve the problem in this paper. Using city edge distance can express multi-centered city situation. The irregular city is easily transformed into a virtual concentric circle city. Then the Clark model and power exponential model are transformed into new format based on the city edge distance. A case study indicates that the transformed formats could successfully simulate the urban population density. But more applications are needed in different city types to validate and improve this distance variable.