Change of water vapor may serve as the largest feedback that influences the climate sensitivity, i.e., amplifies the warming effects due to increases of other greenhouse gases (GHGs) such as atmospheric CO2 concentration. Such positive feedback very likely leads to more frequent extreme weather and climate events. It is essential to analyze the spatio-temporal distribution and long-term trend of atmospheric humidity and water vapor to assess the regional effect of the water vapor feedback to regional climate warming and to understand the mechanism of regional climate response to global warming. Summarizing latest studies, we can confirm that water vapor feedback is a strong positive feedback which could accelerate global warming by one time, and have estimated its range basically although this estimation has large uncertainty. Observational and re-analysis data of water vapor have become more abundant with the development of satellite and radiosonde techniques, but their consistency and homogeneity are far from perfect. Latest climate models could simulate the water vapor feedback in general, but advances in this area are not optimistic. In China, the observation and research in water vapor and its feedback have progressed much during last decades. Water vapor feedback in China is positive for surface temperature in consensus but has large uncertainty for precipitation due to regional climate changes.

Based on the observed daily precipitation records from 540 stations and the 3839 gridded data from a high-resolution regional climate model (CCLM) in 1961-2010, the simulation ability of the CCLM on the daily precipitation in China was examined, and the variation of daily precipitation distribution pattern was revealed as well. By applying the probability method and extreme value theory to the projected data of daily precipitation under the A1B scenario in 2011-2050 by the CCLM, possible trends of daily precipitation series and its extremes were analyzed. Results show that except the western of the Qinghai-Tibet Plateau and South China, distributive patterns of the kurtosis and skewness calculated from the simulated and observed series are consistent with each other, and their spatial correlation coefficients are up to 0.75 or more. The CCLM model can well capture the distribution characteristics of daily precipitation over China. It was projected that in some parts of the Jianghuai region, the mid-eastern part of Northeast China and Inner Mongolia, the kurtosis and skewness will rise significantly, and precipitation extremes will also increase simultaneously in 2011-2050. The increases in projected maximum daily rainfall and largest non-precipitation days in the flood season in the above mentioned regions, also prove the intensified trends of droughts and floods in the next 40 years afar 2010.

Hourly station rain gauge data over South China during 1966-2005 were used to analyze the corresponding relation between precipitation extremes and surface air temperature in the warm season (May to October). The results show that both daily and hourly precipitation extremes in South China increase with temperature rise, and more extreme events show an earlier transition to the two-times Clausius-Clapeyron (CC) relationship. Meanwhile, daily as well as hourly precipitation extremes, present a decrease after the peak point around 25℃, and the decrease of daily precipitation extremes appears to be much more intense. In view of rainfall durations, hourly precipitation extremes are presented by short duration and long duration precipitations individual. Results show that the dramatic decrease of hourly rainfall intensities around 25℃ is mainly caused by short duration precipitation, and long duration precipitation extremes seldom occur when surface air temperature breaks 28℃.

Based on the monthly datasets of 137 sounding stations in eastern China and 160 ground-based stations in whole China in the period of 1980-2009, the variation characteristics of the upper-air temperature over eastern China were analyzed. The results show that 1) the cooling rate in the upper troposphere and the mid-lower stratosphere in the past 30 years, was much more intensive than the warming rate in the mid-lower troposphere; 2) the amplitude of seasonal variation of temperature in northeast China was larger than that in southeast China; 3) in the mid-lower troposphere (from surface layer to 500 hPa) of eastern China, temperatures in different regions and different seasons had different responses to global warming, i.e. there was cooling in south of 35°N but warming in north of 35°N in summers, and the warming took place in winters over the whole study area.

Based on the CRU (Climatic Research Unit) dataset and the output of the historical simulations from 20 CMIP5 models, their simulation capabilities for the climatology and climate variability of the annual mean surface air temperatures in Central Asia have been examined by using Taylor diagram, the trend analysis, and EOF methods. The results show that the 20 CMIP5 models well simulated the significant rise trend, temporal evolution and spatial distribution of the annual mean temperature over Central Asia during 1951-2005, especially the high and low value centers and contour value distributions. The Taylor diagram shows that the root mean square errors are about 0.5 for most models, the spatial correlation coefficients range from 0.85 to 0.90 and the standard deviations range from 0.5 to 1.0. The EOF analysis results show that the 20-model ensemble can better simulate the features of the spatially consistent rise in annual mean temperature and the significant north and south reverse phase fluctuations over Central Asia.

The NCAR Community Atmosphere Model (CAM4.0) was used to investigate the climate effects of land use/land cover change (LUCC). Two simulations, one with potential land cover without significant human intervention and the other with current land use, were conducted. Results show that the impacts of LUCC on diurnal temperature range (DTR) are significant. In the mid-latitudes, LUCC leads to a decrease in DTR, which is mainly caused by the reduction in daily maximum temperature. The reduction in DTR in East Asia of the low latitudes is chiefly the result of the decrease in daily maximum temperature, while in the Indian Peninsula, the decrease in DTR is due to an increase in daily minimum temperature. In general, the LUCC significantly controls the DTR change through the changes in vegetation transpiration and canopy evaporation.

Based on the homogenized observed daily air temperatures from 24 meteorological stations and the NCEP/NCAR reanalysis (R1) air temperature monthly data from 1979 to 2010, the urbanization effect on air temperature changes in the Pearl River Delta region was analyzed by using the observation minus reanalysis (OMR) method. Results indicate that urbanization has significant contribution to the warming in the Pearl River Delta region, especially in winter. The annual mean/maximum/minimum temperature in the Pearl River Delta region increased at a rate of about 0.22℃/10a, 0.19℃/10a, 0.23℃/10a in 1979-2010, accounting for 55.7%, 41.7%, 57.2% of the total warming, respectively. Moreover, the urbanization effect is more obvious on minimum temperature than on maximum temperature.

Based on the input-output survey of farmers and experts in one of the Jiangsu GEF project areas, the cost-benefit analysis method and greenhouse gases estimation method recommended by IPCC were applied to evaluate and compare the social, economic and ecological benefits of the artificial transplanting (ATR), mechanical transplanting (MTR) and direct seeding (DSR) rice under wheat-rice Double Late mode (late rice harvest and late wheat sowing). Results show that the MTR and DSR rice achieved obvious social benefits. Farming measures resulted in lots of man-made greenhouse gases emissions. The ATR rice and wheat rotation mode could obtain the best economic and ecological benefits. The Double Late mode has a good application prospect, but the key of implementing is timely exploiting the recently increased available agricultural climate resources. The cropping pattern of combining the wheat-rice Double Late mode with the ATR is a better choice to mitigate and adapt to climate change.

China is the major producer of chlorodifluoromethane (HCFC-22) in the world. Large amount of fluoroform (HFC-23) was emitted during the production of HCFC-22. Emission factors of HFC-23 were calculated in accordance with the monitoring reports of eleven HFC-23 clean development mechanism (CDM) projects in China and the HFC-23 emissions in 2000-2010 as well as that in 2011-2020 were estimated and projected, respectively. It is expected that, by the end of 2020, emission of HFC-23 in China would be as much as 230 million t CO₂ equivalent. If HCFC-22 producers could voluntarily reduce HFC-23 emissions, it will contribute 3.2%-3.6% to the national CO₂ emission reduction target for 2020.

The current status and development prospects of two major carbon emissions trading systems in the U. S., namely voluntary emission reduction and cap-and-trade system, are reviewed in this paper. Voluntary emission reduction is hard to maintain due to lack of sufficient demand. In order to achieve the carbon reduction targets, the cap-and-trade system should be established to keep continuous carbon trading. Based on the experience from the U. S. Regional Greenhouse Gas Initiative, the Western Climate Initiative and California’s cap-and-trade system, it is suggested that China should have a trial implement of cap-and-trade system firstly in some provinces and industries with suitable conditions; in the beginning, free emission allowance should dominate, supplemented by auction, with restriction of the quantity and scope of carbon offsets. Then it gradually transited to full auction.