"Climate Change 2007? Impacts, Adaptation and Vulnerability", the Working Group II contribution to the IPCC Fourth Assessment Report (AR4) was launched on April 6, 2007. This report summarize the newest peer-reviewed and comprehensive findings from international scientific communities on impact and adaptation. The observed evidence shows that it is likely that anthropogenic warming has had a discernible influence on many physical and biological systems, but many are difficult to discern due to adaptation and non-climatic factors. By the mid-21th century, annual average river runoff and water availability are projected to decrease by 10%~30% over some dry regions at mid-latitudes and in the dry tropics; Approximately 20%~30% of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5~2.5℃; Globally, the potential for food production is projected to increase with increases in local average temperature over a range of 1~3℃, but above this it is projected to decrease. A portfolio of adaptation and mitigation measures can diminish the risks associated with climate change.

Current glacier recession under climate warming has drawn widely attention around the world. Initiated from 1958, the observations of Urumqi Glacier No. 1 at the headwaters of Urumqi River in eastern Tianshan promise the best datasets of glacier and climate changes in China. Taking Urumqi Glacier No. 1 as an example, this paper has analyzed the response of the glacier to the climate change. The results show that during the past 50 years, remarkable changes occurred on the glacier, including snow-firn stratigraphy, glacial zone, glacial temperature (borehole temperature), glacier area, and glacier terminus position etc. These changes are found to be closely related to temperature rise in this area. The glacier retreat appeared throughout the entire observed time period and has shown an accelerated tendency during the last 20 years, particularly after 1995. In addition to summer temperature increase, other two reasons may also be responsible for the acceleration of glacier melting: one is the glacial temperature rise, which reduced the cold reserve in the glacier and thus increased the sensitivity of the glacier to air temperature rise; the other is the decrease of albedo on the glacier surface, which evidently enhanced absorption of radiation.

The Last Glacial Maximum (LGM) is about 21000 calendar years before present, with climate conditions significantly different from the present. Some numerical experiments for this period have been performed in China in recent several years. It is revealed that the LGM was generally characterized by lowered surface temperature relative to the present over China inland, decreased precipitation in the central and eastern China, intensified East Asian winter monsoon and weakened East Asian summer monsoon. Moreover, based on the boundary conditions recommended by the Paleoclimate Modelling Intercomparison Project (PMIP), it is further indicated that vegetation feedback in East Asia, possible ice sheet over the Tibetan Plateau, and sea surface temperature reconstruction in the western Pacific different from the PMIP data source can induce additional climate effects, which partly reconcile model-paleodata discrepancies as displayed by the standard PMIP simulations.

Based on review of the main progresses in precipitation extremes under the background of global warming, this study discusses the character of change in precipitation extremes. It indicates that during the recent 50 years, in most parts of China, the number of precipitation days has decreased significantly except in Northwest China, while the precipitation intensity has increased significantly. In North China, the precipitation extreme has decreased, but the proportion of extreme precipitation to the total has increased relatively; the intense precipitation extreme has become frequently in the western Northwest China, over and to the south of the Yangtze River. The annual precipitation amount from wet spells has decreased significantly in North China, eastern Northeast China and the eastern part of Southwest China, but increased in the eastern Tibetan Plateau and some southeast coastal areas. The number of days of trace precipitation has decreased is an important drought tendency. The relationship between extreme precipitation and total precipitation is very complicated under the impact of climate warming.

In the summer of 2006, severe heat wave and drought hit Chongqing municipality and Sichuan Province, causing dramatic economic losses and environmental damages. The comprehensive effect of the weather-related disturbances and global warming may be the reasons for the occurrence of the warm extremes in Chongqing and Sichuan in the summer of 2006, but the random weather-related disturbances contribute most to the local warm extremes in last summer. It is indicated that less cold air activities, northward locations of subtropical high ridgeline, and less snow cover over the Tibetan Plateau in the winter and spring of 2005/2006 are the main three direct causes for the extremely hot and dry weather over the above-mentioned areas in the summer of 2006.

Studies on extratropical cyclones under the climate warming background have attracted particular concern in recent years. Most of these researches focused on the characteristics of interannual or interdecadal variations of cyclone frequency, intensity and storm tracks. The consensus indicated that cyclone frequency by statistics has significantly decreased in mid-latitudes, but increased in high-latitudes. Storm intensity has increased in both high- and mid-latitudes during the past 50 years. The global warming might have resulted in a northward shift of storm tracks in the Northern Hemisphere. In addition, cyclone activities have good relations with tropospheric baroclinity, westerly jet, and sea surface temperature (SST) gradient.

It is summarized the projections of typhoon changes over the western North Pacific Ocean for the 21st century in the recent years. Multi-model ensembles with the various human emission scenarios indicate that the total numbers of the annual typhoons simulated over the western North Pacific Ocean might decrease by the end of the 21st century. But the numbers of the strong typhoons simulated and the intensities of their wind speed and precipitation might increase at the same time. It must be emphasized that the long-term projection of the typhoons is a very difficult issue, the further studies will be conducted in future to narrow the gaps and uncertainties. The mechanisms and feedbacks between the human activities and typhoon changes should be investigated in detail.

In this paper, we review basic methods for projecting possible future changes in extreme events, with an emphasis on the analysis of output from high resolution climate models. Current and past research on extreme events in East Asia and China are discussed and the projections for China are summarized, including existing problems in these projections. It is pointed out that further studies in the following areas are needed in order to better project future extreme events over China: higher spatial and temporal resolution gridded observational data, extended high resolution regional climate model simulations, multi-model ensembles, and the application of statistical downscaling. In addition, the effects of land use and atmospheric aerosols must be considered in model simulations.

The multi-scale characteristics of the reconstructed temperature and glacier ice accumulation from Guliya ice core on the Tibetan Plateau are studied by orthogonal wavelet decomposition. The main characteristics of the two sequences can be almost totally reproduced by the components with the scales longer than 100 years, and the well-known climate events in the records can be fitted well by only one or several decomposed components. In addition, the records also show some unsteady properties of their components, by which a number of transient climate events can be interpreted well. Meanwhile the unsteadiness also exists in their collocation evolution although their correlation coefficients are almost positive except for the one at scale 130 years. Besides, the linear trend of temperature and millennia-scale components of the two sequences dominated their collocation evolution during 301-1990 AD.

Based on the Pinus tabulaeformis tree-ring records from Mt. Kongtong, this paper focused on its environment change history. After laboratory approaches like mounting, polishing, cross-dating and high precision measuring, 66 tree-ring cores are used to establish three types of tree-ring width chronologies: standard chronology (STD), residual chronology (RES), and autoregression standard chronology (ARS). Correlation analysis between the chronologies and meteorological observation data shows that the standard tree-ring index has the best correlation with the average temperature of summer. Regression model is also founded according to the analysis results. Different verification results show that the regression model is stable and reliable. The summer average temperature sequence during the period of 1751-2005 is reconstructed, and it exhibits three cold periods: 1764-1785, 1852-1893, 1952-1986 and three warm periods: 1786-1847, 1894-1937, 1987-2004. Comparisons of the temperature with Nino3 index, SOI index and sunspot number suggest that the study area has good response to global climate change and solar activities.

Since post-Kyoto negotiations launched, there have been increasing discussions and debates on international climate regime at international level. In August 2006, Brazilian team of the BASIC project put forth a comprehensive package as a basis of an agreement on post-Kyoto international climate regime, known as the Sao Paulo Proposal. In this paper, the principles and key elements of the proposal such as global objective in long term, differentiated commitments of Annex I and non-Annex I Parties, market mechanisms, adaptation, technology research and development and transfer, as well as review and compliance of the proposal protocol are briefly introduced. Then, a preliminary assessment is conducted by comparing with the Brazilian Proposal and by pointing out its inherent limitations on political barriers and technical difficulties.