This study assesses projection skill of Arctic Oscillation (AO) in initialized decadal experiment with the Beijing Climate Center Climate System Model (BCC_CSM1.1). As compared with the observations and uninitialized historical experiment, the contribution of climate model initialization to predict the seasonal scale AO and its interannual variations is estimated. Results show that the spatial correlation coefficient of AO mode, which depicts the dominant mode of the extra-tropical atmospheric variability, simulated by the decadal experiment is higher than that in the historical experiment. The two groups of experiments can basically reproduce the characteristics of the strongest winter AO index and the weakest summer index. Compared with historical experiment, the correlation coefficient of the monthly and winter AO index is higher in the decadal experiment. In particular, the correlation coefficient of the monthly AO index between the decadal simulations and the observation reached 0.1 significant level. Furthermore, the periodicity of the monthly and spring AO index are achieved only in the decadal experiment. Hence, the hindcast skill of AO is robust when the initial state is initialized by sea surface temperature data.

Based on monthly gauged rainfall data in Northeast China and the global atmospheric and oceanic reanalysis dataset for 1961-2015, the decadal changes of rainfall in May over Northeast China (NEC) as well as its relationship with atmospheric circulation and sea surface temperature were investigated using statistical and diagnostic methods. Different from that in late-summer, the rainfall in May over NEC depicted negative anomalies during 1984-1993 and positive anomalies during the early 21st century. The decadal changes of rainfall in May over NEC is mainly attributed to the decadal variation of Northern East Asian Low (NEAL) in May. During the early 21st century, the NEAL was much stronger than its climatology, resulting in surplus rainfall over NEC. Nevertheless, the NEAL was weakened into a shallow trough during 1984-1993, leading to deficient rainfall over NEC. A wave train in the geopotential height field over the Eurasia causes significant vertical motion over the Northern East Asia, which contributes to the above variation of the NEAL. The sea surface temperature anomalies over the tropical North Atlantic in May is the possible external forcing generating the above wave train, which gives rise to the corresponding decadal changes of rainfall over NEC.

Taking the Lancang River Basin as the study area, the ISIMIP2b protocol having provided four global climate models: GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-LR, MIROC5, combining with the VIC model, the ability of simulation, on the extreme value of flood peak and flood volumes (annual maximum flood peak flow, the maximum flood volumes during three days) and extreme floods, was analyzed, in the historical periods (from 1961 to 2005). The changes of average annual runoff volume in the future periods (from 2021 to 2050) compared with the base periods (from 1971 to 2000) under the two scenarios of RCR2.6 and RCP6.0 were also analyzed. Then the P-III distribution curve was combined to predict the intensity of extreme floods in the Lancang River Basin in the future periods. The VIC model can better simulate extreme flood in this basin. The output datas of HadGEM2-ES and MIROC5 climate models have good applicability for runoff simulation in the Lancang River Basin; in the scenario of RCP2.6, the average annual runoff volume in the Lancang River Basin does not change significantly in the future, and may increase slightly, while in the scenario of RCP6.0, the average annual runoff in the future may increase significantly compared with the historical periods; the extreme floods in the Lancang River Basin in the future periods, have no obvious changes under the RCP2.6 scenario. While, under the RCP6.0 scenario, the flood peak and flood volumes are more likely to increase, and frequency and intensity of the extreme floods are also likely to increase.

The atmospheric heat source (AHS) over Tibetan Plateau (TP) during 1980-2016 was calculated using four reanalysis data (NCEP/DOE, MERRA2, ERA-Interim and JRA-55 data), and the uncertainties was also discussed. The main conclusions are as follows: (1) Methods and data can both make deviation. Indirect method can not only get the whole layer of AHS, but also the vertical structure of AHS, while its estimation precision mainly depends on reanalysis data. (2) Compared with four reanalysis data, we found that adopting two methods with ERA-Interim data can get consistent inter-decadal variation of AHS over TP, while the AHS value calculated by direct method is greater than the indirect method. The results from four reanalysis data by indirect method obtained the obviously identical decadal variation during 1980-2016. (3) Positive AHS mainly distributed in the center and eastern of TP during March-August, and the vertical structure of AHS is “source-sink-source” from surface to high troposphere. (4) The results revealed that latent heat flux calculated by ERA-Interim data is stronger in the western and southern Gangdise, and is weaken in the south slope of Himalaya range.

To have a more complete evaluation of the solar geoengineering effect on global climate, it is of great importance to examine the effects of geoengineering on ocean acidification. In this study the UVic Earth System Model was used to simulate the effects of solar geoengineering on sea surface pH and aragonite (a metastable form of calcium carbonate) saturation (Ω). We run the UVic model from pre-industrial to the year 2100 under RCP8.5 scenario, and quantified the effects of individual environment factors on ocean acidification. The simulations show that by the year 2100, relative to pre-industrial levels, global mean sea surface pH would decrease by 0.43 and Ω state will decrease by 1.77. Relative to the RCP8.5 scenario without geoengineering, by the year 2100, solar geoengineering would increase sea surface pH by 0.003, but decrease Ω by 0.16. Relative to the RCP8.5 scenario without geoengineering, geoengineering-induced increase of dissolved inorganic carbon would decrease pH and Ω, but the increase of alkalinity would increase pH and Ω. Geoengineering-induced decrease of temperature would increase pH but decrease Ω. The net effect of solar geoengineering on pH and Ω is small. Our study indicates that solar geoengineering could cool the earth but fails to mitigate ocean acidification.

In this paper, a GDP projection model was constructed based on the Cobb-Douglas production function and the Autoregressive Integrated Moving Average (ARIMA) model. Under the consideration of balanced development the Gini coefficient of provincial GDP per capita was used to measure the degree of development balance. This model projects Chinese provincial GDP and GDP per capita from 2016 to 2050. Based on the balanced development from technology, labor, and capital. The projection results show that from 2016 to 2050, the gap between the GDP and GDP per capita in each province will shrink and the Gini coefficient will decline. In this projection, the Gini coefficient will decrease from 0.219 in 2015 to 0.176 in 2030 and then to 0.137 in 2050. The results also show that development of each province will tend to be balanced in the future.

Based on the meteorological and animal phonological observations in Qingdao, the characteristics of climate and phonological changes and their relations were investigated. From 1986 to 2016, the first song days of animals in Qingdao respectively exhibit smoothly fluctuations for Cryptotympana atratas, first delaying and then advancing trend for crickets, and distinct delaying trend for Hirundo rusticas and frogs. All their last song days display a significant advancing trend, and their first-last song intervals have a remarkable shortening trend. Under the influence of global warming, the temperature rises significantly, the precipitation changes a little, but the annual sunshine durations and wind speed both present a trend of dramatic decrease during 1961-2016 in Qingdao. The decrease for sunshine durations affects phenophase the most for the four animals, which is beneficial to advancing the last song days and shortening the first-last song intervals for all, and delaying the first song days for Hirundo rusticas. The phenophase for crickets and frogs responds notably to the temperature rising, but not for Cryptotympana atratas and Hirundo rusticas. The decreasing wind speed helps advancing the last song days and shortening the first-last song intervals for Cryptotympana atratas and Hirundo rusticas, but is conducive to delaying the last song days and extending the first-last song intervals for frogs. Hence, the phenophase variation occurs in conjunction with several climate factors. Except for the influence from climate change, the inter-restriction of food chain among animals also plays a role in causing the phenophase variation.

Current studies show the withdrawal of the U.S. from the Paris Agreement will lead to an increase of 1.2 Gt CO₂-eq in its own emission by 2025. However, the effect of the U.S.’s withdraw does not limit to the effect on its own emission, but also have impacts on global emission through indirect impacts such as financial effect, political effect and inertia effect. In this study, various global emission scenarios were built to model the different effects caused by the U.S.’s withdrawal from the Paris Agreement. The results show that the self-effects, financial effects, political effects on umbrella countries, and political effects on developing countries will lead to an increase in net global greenhouse gases (GHGs) emissions by 2.0, 1.0, 1.0 and 1.9 Gt CO₂-eq, respectively in 2030, and will lead to an increase in 2100 cumulative GHGs emissions by 246.9, 145.3, 102.0 and 270.2 Gt CO₂-eq, respectively. To manage the negative impact of the U.S.’s withdrawal, China should take the lead actively on the establishment and development of global climate governance, cooperate with other countries closely to promote the implementation of the Paris Agreement in a comprehensive and balanced manner.

The EKC relationship between GDP and greenhouse gas (GHG) emissions shows an inverted U-shape based on the GHG emissions accounting data in Heilongjiang province from 2001 to 2015, and the curve is expected to reach inflection point in 2019. The results of average annual emission reduction of 4 paths by partial least-squares regression model are as follows: the reduction of energy consumption per unit GDP, the adjustment of economic structure, the growth of per capita GDP, the change of trade structure. The dynamic impact effects for corresponding impulse response functions are fluctuating emission increase, convergent emission reduction, divergent emission reduction, and transformational emission effect. The paths order of promoting GHG emission reduction in Heilongjiang province is to control fossil energy consumption, optimize economic structure, develop low-carbon economy and adjust trade structure.

During the process of CO₂ geological sequestration suitability evaluation with analytic hierarchy method, problems include that weight of low level evaluation index is calculated with little consideration of the real research region and suitability evaluation result isn’t studied further. To solve the above problems, through calculating the index composition weight and suitability score, CO₂ geological sequestraion suitability evaluation in Ordos Basin was carried out combined with its geological feature. Then, the research of caprock closure, taking the Chang 4+5 layer in Xingzichuan oilfield for example was done. At the same time, CO₂ geological sequestration potential in deep saline aquifer and reservoir was calculated with corresponding methods. Calculated results show that the CO₂ geological sequestraion suitability in Triassic is the best, closely followed by Carboniferous-Permian and Ordovician. Meanwhile, sealing ability of Chang 4+5 caprock in Xingzichuan oilfield is good for CO₂ geological sequestraion. Moreover, the potential of CO₂ geological sequestration in deep saline aquifer and reservoir is 1.33×10 ¹⁰ t and 1.91×10 ⁹t, respectively. In addition, there are 56 suitable areas in Wuqi, Jingbian and Xingzichuan blocks in Yanchang Petroleum and its CO₂ geological sequestraion potential is about 1.77×10 ⁸ t.