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Since climatic condition is the important foundation for human subsistence and development and the key factor in sustainable development of economy and society, climate change has been a global issue attracting great attentions of politicians, scientists, governments, and the public alike throughout the world. Existing climate regionalization in China aims to characterize the regional differences in climate based on years of the mean value of different climate indexes. However, with the accelerating climate change nowadays, existing climate regionalization cannot represent the regional difference of climate change, nor can it reflect the disasters and environmental risks incurred from climate changes. This paper utilizes the tendency value and fluctuation value of temperature and precipitation from 1961 to 2010 to identify the climate change quantitatively, and completes the climate change regionalization in China (1961-2010) with county administrative regionalization as the unit in combination with China's terrain feature. Level-I regionalization divides China's climate change (1961-2010) into five tendency zones based on the tendency of temperature and precipitation, which are respectively Northeast China-North China warm-dry trend zone, East China-Central China wet-warm trend zone, Southwest China-South China dry-warm trend zone, Southeast Tibet-Southwest China wet-warm trend zone, and Northwest China-Qinghai-Tibet Plateau warm-wet trend zone; level-II regionalization refers to fourteen fluctuation regions based on level-I regionalization according to the fluctuation of temperature and precipitation. [ABSTRACT FROM AUTHOR]

Terrestrial vegetation is one of the most important components of the Earth's land surface. Variations in terrestrial vegetation directly impact the Earth system's balance of material and energy. This paper describes detected variations in vegetation activity at a national scale for China based on nearly 30 years of remote sensing data derived from NOAA/AVHRR (1982-2006) and MODIS (2001-2009). Vegetation activity is analyzed for four regions covering agriculture, forests, grasslands, and China's Northwest region with sparse vegetation cover (including regions without vegetation). Relationships between variations in vegetation activity and climate change as well as agricultural production are also explored. The results show that vegetation activity has generally increased across large areas, especially during the most recent decade. The variations in vegetation activity have been driven primarily by human factors, especially in the southern forest region and the Northwest region with sparse vegetation cover. The results further show that the variations in vegetation activity have influenced agricultural production, but with a certain time lag. [ABSTRACT FROM AUTHOR]

Global climate change and its possible ecological consequences have become the focused issue (IPCC, 2007; Mann et al., 2008; Ding et al., 2009). The Holocene contains the analogous characteristic of future climatic change and the continuous agriculture activity, providing the ideal “similar pattern” for studying the climate change and human adaption and impact in the future. Based on the recent studies of stalagmite, ice core, ocean, and lake etc., the paper introduces the new progress in the Holocene climate and agriculture research in China as follows: (1) Discuss the variability, amplitude, and unstable characteristic of climate, as well as the abrupt events and mechanisms of climate. (2) Analyze the botanical index records for studying the early agriculture. (3) Review the agricultural origin, expanding, and development. (4) Reveal the style and intensity of early agriculture and understand the agricultural impact and adaption to the environmental changes. (5) Introduce ongoing research projects in China and emphasize the significance of increasing the dating precision and the indicative effectiveness of proxies. (6) Realize how the ecosystem and environmental factors respond to the increasing temperature process, understand how the human adapt to the rapid climate change, and provide the scientific basis for assessing the effects of climate change and the human adaption in the future. [ABSTRACT FROM AUTHOR]

As an important part of the regional environment, the wet-dry climate condition is determined by precipitation and potential evapotranspiration (expressed as ET ). Based on weather station data, this study first calculated ET by using the FAO56 Penman-Monteith model. Then, the dryness index K (ratio of ET to precipitation) was used to study the spatio-temporal variation of the wet-dry condition in China from 1961 to 2015; moreover, dominant climatic factors of the wet-dry condition change were discussed. The annual precipitation and ET of the Qinling-Huaihe line were close to a balance ( K≈1.0). The annual precipitation in most areas exceeded the ET in the south of this line and the east of Hengduan Mountains ( K<1.0), where the climate is wet. Furthermore, the precipitation in the northwest inland areas of China, where the climate is dry, was markedly lower than ET ( K≥4.0). The overall annual K of China fluctuated around the 55-year mean and its linear trend was not significant. However, a relatively wet period of about 10 yr (1987-1996) was recorded. The overall annual K of China showed strong cyclicality on the time scale of 3, 7-8, 11 and 26-28 yr, and regional differences of the annual K trends and cyclicality were large. The degrees of wetness in the Northwest China and western Qinghai-Tibet Plateau were substantially increased, whereas the degrees of dryness in the Yunnan-Guizhou Plateau, Sichuan Basin, and Loess Plateau were markedly increased. The linear trend of the annual K in most regions of China was not significant, and the annual K of most areas in China showed strong cyclicality on the 8-14 yr time scale. Precipitation was the dominant factor of wet-dry condition change in most areas, especially in North China, where the annual K change was highly correlated with precipitation. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) can interact with other trace chemicals in the atmosphere, significantly impacting atmospheric chemistry and global climate change. China is a largely agricultural country with high consumption of nitrogen fertilizer and large livestock herds, resulting in high NH3 emissions. In this study, a comprehensive county-level inventory of Chinese NH3 emissions from 2013 to 2018 was compiled. Based on previous research, an estimate of NH3 emissions from household coal combustion was added to the inventory. The estimation of emissions from open biomass burning was improved by using a method based on fire radiative energy (FRE). The total NH3 emissions in China increased from 2013 (9.64 Tg) to 2015 (9.75 Tg), and then decreased to 9.12 Tg in 2018. Emissions from fossil fuels reached a peak value in 2018, accounting for 8.4% of total emissions, while fertilizer application and livestock waste were responsible for fewer emissions than in previous years, accounting for 27.7% and 49.9% of the total from non-fossil fuel sources, respectively. The highest emission rates were in central and southwestern China. Seasonally, NH3 emissions peaked in spring and summer. The inventory had a 1-km spatial resolution and a monthly temporal resolution, which confirmed its suitability for global and regional air quality simulations. [ABSTRACT FROM AUTHOR]

Phenology is a reliable biological indicator for reflecting climate change. An examination of changes in crop phenology and the mechanisms driving them is critical for guiding regional agricultural activities in attempts to adapt to climate change. Due to a lack of records based on continuous long-term observation, studies on changes in multiple consecutive phenological stages throughout a whole growing season on a national scale are rarely found, especially with regard to the spatiotemporal differentiation of phenological changes. Using a long-term dataset (1981-2010) of wheat phenology collected from 48 agro-meteorological stations in China, we qualified the spatiotemporal changes of 10 phenological stages as well as the length of wheat growth phases. Results showed that climate and wheat phenology changed significantly during the growing seasons from 1981 to 2010. On average, on a national scale, dates of sowing (0.19 d a-1), emergence (0.06 d a-1), trefoil (0.05 d a-1), and milk ripe (0.06 d a-1) showed a delaying trend, whereas dates of tillering (-0.02 d a-1), jointing (-0.15 d a-1), booting (-0.21 d a-1), heading (-0.17 d a-1), anthesis (-0.19 d a-1), and maturity (-0.10 d a-1) showed an advancing trend. Furthermore, the vegetative growth phase and growing season were shortened by 0.23 and 0.29 d a-1, respectively, whereas the reproductive growth phase was lengthened by 0.06 d a-1. Trends in dates of phenological stages or length of growing phases varied across wheat-planting regions. Moreover, spatiotemporal differentiation of sensitivity in growing season length (GSL) to variations in climatic factors during the growing season between spring and winter wheat were remarkable. The GSL of spring (winter) wheat decreased (increased) with an increase in average temperature during the growing season. In all wheat-planting regions, the GSL increased with the increasing of total precipitation and sunshine duration during the growing season. In particular, the sensitivity of GSL to precipitation for spring wheat was weaker than for winter wheat, while the sensitivity of GSL to sunshine duration for spring wheat was stronger than for winter wheat. Recognition of the spatiotemporal differentiation of phenological changes and their response to various climatic factors will provide scientific support for decision-making in agricultural production. [ABSTRACT FROM AUTHOR]

Five General Circulation Model (GCM) climate projections under the RCP8.5 emission scenario were used to drive the Variable Infiltration Capacity (VIC) hydrologic model to investigate the impacts of climate change on hydrologic cycle over continental China in the 21st century. The bias-corrected climatic variables were generated for the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5) by the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP). Results showed much larger fractional changes of annual mean Evapotranspiration (ET) per unit warming than the corresponding fractional changes of Precipitation (P) per unit warming across the country, especially for South China, which led to a notable decrease of surface water variability (P-E). Specifically, negative trends for annual mean runoff up to −0.33%/year and soil moisture trends varying between −0.02% to −0.13%/year were found for most river basins across China. Coincidentally, interannual variability for both runoff and soil moisture exhibited significant positive trends for almost all river basins across China, implying an increase in extremes relative to the mean conditions. Noticeably, the largest positive trends for runoff variability and soil moisture variability, which were up to 0.41%/year and 0.90%/year, both occurred in Southwest China. In addition to the regional contrast, intra-seasonal variation was also large for the runoff mean and runoff variability changes, but small for the soil moisture mean and variability changes. Our results suggest that future climate change could further exacerbate existing water-related risks (e.g., floods and droughts) across China as indicated by the marked decrease of surface water amounts combined with a steady increase of interannual variability throughout the 21st century. This study highlights the regional contrast and intra-seasonal variations for the projected hydrologic changes and could provide a multi-scale guidance for assessing effective adaptation strategies for China on a river basin, regional, or as a whole. [ABSTRACT FROM AUTHOR]

Soil respiration is an important process in terrestrial carbon cycle. Concerning terrestrial ecosystems in China, quantifying the spatiotemporal pattern of soil respiration at the regional scale is critical in providing a theoretical basis for evaluating carbon budget. In this study, we used an empirically based, semi-mechanistic model including climate and soil properties to estimate annual soil respiration from terrestrial ecosystems in China from 1970 to 2009. We further analyzed the relationship between interannual variability in soil respiration and climatic factors (air temperature and precipitation). Results indicated that the distribution of annual soil respiration showed clear spatial patterns. The highest and lowest annual soil respiration rates appeared in southeastern China and northwestern China, respectively, which was in accordance with the spatial patterns of mean annual air temperature and annual precipitation. Although the mean annual air temperature in northwestern China was higher than that in some regions of northeastern china, a greater topsoil organic carbon storage in northeastern China might result in the higher annual soil respiration in this region. By contrast, lower temperature, less precipitation and smaller topsoil organic carbon pool incurred the lowest annual soil respiration in northwestern China. Annual soil respiration from terrestrial ecosystems in China varied from 4.58 to 5.19 Pg C a between 1970 and 2009. During this time period, on average, annual soil respiration was estimated to be 4.83 Pg C a. Annual soil respiration in China accounted for 4.93%-6.01% of the global annual soil CO emission. The interannual variability in soil respiration depended on the interannual variability in precipitation and mean air temperature. In order to reduce the uncertainty in estimating annual soil respiration at regional scale, more in situ measurements of soil respiration and relevant factors (e.g. climate, soil and vegetation) should be made simultaneously and historical soil property data sets should also be established. [ABSTRACT FROM AUTHOR]

Multi-decadal high resolution climate change simulations over East Asia were performed by using The Abdus Salam International Centre for Theoretical Physics (ICTP) Regional Climate Model (RegCM3), nested within the NASA/NCAR global model FvGCM/CCM3. Two sets of simulations were conducted at 20-km grid spacings, one for present day (1961-1990) and one for the future climate (2071-2100, IPCC A2 scenario). Simulations of present climate conditions over China by RegCM3 and FvGCM were compared against observations to assess the model performance. Results showed that both models reproduced the observed spatial structure of 500 hPa height, surface air temperature and precipitation. Compared with FvGCM, RegCM3 provided increasing spatial detail of surface variables. Furthermore, RegCM3 improved the simulation of monsoon precipitation over the region. Changes in the mean temperature and precipitation were analyzed and compared between the two models. Significant warming in the end of the 21st century was simulated by both models in December-January-February (DJF), June-July-August (JJA), and the annual mean. In DJF, greater warming was simulated by FvGCM over Northeast and Northwest China, as well as the Tibetan Plateau, compared with RegCM. In JJA, RegCM3 simulated greater warming over northern China, Inner Mongolia, Northwest China, and the Tibetan Plateau. Simulated changes in DJF precipitation showed similar spatial patterns between the two models. In JJA, while FvGCM projected a prevailing increase of monsoon precipitation over China, which is in agreement with other global models, RegCM3 projected extended areas of decreased precipitation. Changes in the variability for annual mean temperature and precipitation also are presented. [ABSTRACT FROM AUTHOR]