Based on the review of the successive four assessment reports of the IPCC WGII on climate change impacts on streamflow from 1990 to 2007, it is summarized that the First (FAR) and Second (SAR) Assessment Reports were regarded as the first generation studies, featuring the impacts of mean climate change on streamflow and the adaptation to it, while the Third (TAR) and Forth (AR4) Assessment Reports as second generation studies, emphasizing the impacts of anthropogenically forced and natural climate changes on streamflow and the adaptation to them. The progresses and issues in the research methodologies of the impacts of climate change on hydrology and water resources are analyzed. It is pointed out that the impacts of decadal and multi-decadal variability of climatic variables on streamflow can be identified, but changes in interannual and daily variabilities are not taken into account in the conventional methodology of hydrological impact studies. As the results, the impacts of climate change on extreme events, such as droughts, floods and irrigation water demands are underestimated. As for further studies, the paper comes to conclusion suggesting to emphasize the interdisciplinary science study of hydrology and climatology in the next IPCC Assessment Report.

The issue of water shortage and related eco-environmental degradation in North China is one of the major emerging problems in China. Precipitation is the most important factor for water resources. Based on the historical series of instrumental data of annual precipitation obtained from 25 gauging stations and a long-term historical drought-flood grade dataset during the period of 1470-2000 obtained from 15 gauging stations in North China, the character of precipitation variability was analyzed by means of power spectrum and continuous wavelet transform. It was found that the precipitation was characterized by obvious seasonal changes, quasi-biennial oscillation, and quasi-19-year interdecadal periodicity. The M-K test results showed that abrupt changes in annual precipitation occurred around 1914 and 1964. As for the historical flood/dryness grade time series, it was characterized by the 4-5-year ENSO mode interannual oscillation, the quasi-10-year and quasi-24-year interdecadal variabilities and 50-80-year centurial periodicity.

Based on projected runoff depth of ECHAM5/MPI-OM climate model for the Yangtze River basin under different GHG emission scenarios (SRES-A2, A1B, B1) in 2001-2050, the temporal and spatial patterns of future surface water resource in the Yangtze River basin were analyzed. The results show that the long-term average annual surface water resources of the Yangtze River under three scenarios are similar, while interannual fluctuations are complicated with different trends. The surface water resource declines gradually in fluctuation under the A2 scenario, shows no obvious trend under the A1B scenario, and displays a relatively significant increasing trend under the B1 scenario. Decadal variations of the surface water resource are notable, showing an overall decline trend under all the three scenarios in 2001-2030, while an increase trend to varying extent after the 2030s, especially in summer and winter. The projected future water resource in the Yangtze River remains the current level, showing an evident spatially uneven feature.

Based on the average discharge of the Hotan River and the 0℃ level height data measured in summer at 3 hydrological and meteorological stations in the Hotan River basin, and the reanalyzed 500 hPa temperature from NCEP/NCAR, the relations of the discharge of the Hotan River with the 0℃ level height and the 500 hPa temperature were analyzed. The results are as follows: the summer average discharge and 0℃ level height decreased slightly in the Hotan River basin during 1961-2004, both the time series changed abruptly from high to low value in 1979. There were distinctive differences in summer 500 hPa temperature anomalies in the Northern Hemisphere between the typical high and low flow years of the Hotan River. The average discharge responded notably on interannual and interdecadal scales to changes of regional 0℃ level height in the Hotan River basin.

Trends in frequencies of daily precipitation at nine different levels over the last 45 years have been analyzed in this article, using the daily precipitation data from 1961 to 2005 in Ningxia. It has been found that the annual precipitation decreased at a mean rate of 3.6 mm/10 a. In the recent 15 years, precipitation obviously decreased in winter and spring; in summer and autumn, days of precipitation below 10.0 mm obviously decreased, but days of precipitation over 25.0 mm significantly increased. Differences in summer and yearly days of precipitation in 25.1-50.0 mm before and after 1986 were statistically significant at 5% and 1% level, respectively. The extreme trends of precipitation are obvious in Ningxia.

The direct effects of black carbon (BC) aerosols over China on East Asian summer monsoon have been investigated using the latest version of general circulation model (GCM) CAM3.0 developed by NCAR/UCAR, which is coupled with an off-line aerosol assimilation system. The model results show that BC aerosols over China can bring about a global average radiative forcing of 0.13 W/m2, resulting in the decrease of land surface temperature in most of China except for Qinghai, Tibet and Guangxi provinces where the surface temperature increased. Therefore, the differences in surface temperature and pressure between land and sea reduce, which finally weakens East Asian summer monsoon. BC aerosols have less effect on weakening monsoon intensity compared with sulfate aerosols. However, it increases precipitation, especially convective precipitation in the middle and lower reaches of the Yangtze River. On the contrary to sulfate aerosols, BC aerosols enhance the convective activities in the southeast of China. Besides, the joint effect of BC and sulfate aerosols over China has also been studied. The model results indicate that the synthetic effect of sulfate and BC aerosols is similar to that of sulfate aerosols only, and precipitation changes induced by the joint effect are also consistent with those by the sulfate aerosols effect.

Considering the lack of spatial and temporal accuracy, poor reliability of global climate models (GCM) at regional or local scale, a statistical downscaling model (SDSM) is used to generate daily weather data. With SDSM, the daily series of HadCM3 outputs under the A2 and B2 scenarios were downscaled to the stations. The future trends of annual precipitation, daily maximum (TMAX) and mininum temperatures (TMIN) in the upper-middle reaches of the Yellow River were analyzed on the basis of the reference period of 1961-1990. Daily TMAX and TMIN both show increasing trends under the A2 and B2 scenarios, but the increment is more distinct under the A2 scenario. The increasing trends of TMAX at Jingtai station and TMIN at Hequ station are the most remarkable. The increment in annual precipitation in the basin ranges from -18.2% to 13.3%. Under the A2 scenario, the areas with an increasing trend and a decreasing trend are almost equal, and the largest increment occurs at Baoji station. Under the B2 scenario, the annual precipitation shows a decreasing trend in most parts of the basin, and the largest reduction appears at Xifengzhen station.

Using the monthly mean temperature, precipitation at a grid resolution of 0.5°×0.5° in Central China during 1961-1990 and 2001-2030 simulated by regional climate model of National Climate Center under SRES A2, and the actual monthly mean temperature, precipitation during 1961-1990 in all basic and standard stations in the area, the climate change tendency was estimated and analyzed for the first 30 years of the 21st century. The results show that, relative to the period 1961-1990, annual mean temperature during 2001-2030 in Central China generally has a warming tendency of 0.3℃, and it will increase more quickly in the east than in the west of the area. The annual precipitation in Central China mostly presents a decreasing tendency, but an increasing tendency in the south part. The mean temperature will increase by 0.1-1.3℃ and 0.8-2.2℃ in spring and summer, respectively, decrease in the north and increase in the south in autumn, and decrease by 0.0-1.0℃ in winter. In most areas of Central China, precipitation will decease in spring, summer and winter, especially in winter, and increase in autumn.

By using 541-station uniform maximum temperature in China, the temporal and spatial distributions of yearly high temperature days with daily maximum temperature ≥35℃ and their responses to global warming were analyzed. The results show that the average high temperature days have two high centers in Turpan Basin and Jiangnan region. The high temperature days have an evolutional trend of increasing-decreasing-increasing and show the significant 3-year period in Xinjiang and the 3- to 6-year period in the 4 regions of eastern China. The time of trend changing from decreasing to increasing is not synchronous for the whole country, and it gets later with the increasing latitude.

Based on the daily precipitation data in summer (JJA) for the period from 1961 to 2006 at 52 observation stations, temporal and spatial characteristics, periodical variations and abrupt changes of summer rainstorm in Guizhou were investigated. The results indicate that rainstorm precipitation increased in the past 46 years and its interannual and decadal variations were remarkable . The abrupt changes in the rainstorm precipitation and day number both occurred in 1985. There were periodical variations of 15 years and quasi-10 years in both summer rainstorm precipitation and day number. The first EOF eigenvector field of summer rainstorm day number was consistent with that of summer rainstorm precipitation, showing consistent in-phase distribution of rainstorm in Guizhou.

With a brief introduction of the background and framework of programmatic clean development mechanism (P-CDM) projects, the dilemma of developing P-CDM projects was analyzed, including the approval process in the designated national authority (DNA), technical barriers in the project design phase, the validation and verification processes undertaken by designated operational entity and the sale of emission reductions. From the perspective of policy choices, the paper gives some advices on above-mentioned issues, i.e., the DNA should further improve the management approach, make full use of advances of industry organizations and scientific research institutes in solving the technical problems in P-CDM development, promote and strengthen the construction of P-CDM market via 'Mass Effect', and cooperate with relevant parties in simplifying the international rules to really reduce transaction costs of P-CDM project development.