Abstract:

Earths mean surface temperature has increased by about 08℃ since the early 20th century, with about twothirds of the increase occurring since 1980. The Intergovernmental Panel on Climate Change (IPCC) indicated that the Earths average surface temperature rose by 074℃±018℃ over the period of 1906-2005. The rate of warming over the last half of that period was almost doubles than that for the period as a whole (013±003℃ per decade, versus 007℃±002℃ per decade). During the 21st century, the global surface temperature is likely to rise a further 11℃ to 29℃ for their lowest emissions scenario and 24℃ to 64℃ for their highest. Observations as well as most climate model simulations are generally in accord with the hypothesis that the hydrologic cycle should intensify and become highly volatile with the greenhousegasinduced climate change, although uncertainties of these projections as well as the spatial and seasonal variability of the changes are much larger than that for temperature extremes. The likely effects of the warming include a more frequent occurrence of extreme weather events including heat waves, droughts and heavy rainfall, ocean acidification and species extinctions due to shifting temperature regimes. The effects are significant to humans including the threat to food security from decreasing crop yields and the loss of habitat from inundation, which will change humans living environment. Water resource is an important restricted factor for social and economic sustainable development in the Dry valleys of Hengduan Mountains. By using 24 meteorological stations in monthly precipitation (P) and temperature (t) observation data, on the basis of Taka hashis evaporation equation, the ground evaporation (E) and available precipitation (PE) related to water resources were calculated. The following conclusions were obtained. Short of precipitation and huge evaporation were typical feature in dry valleys in Hengduan Mountains, the annual average rainfall only about 7237 mm, the average annual evaporation capacity up to 4795 mm, more than 8489% of rainfall were evaporated, and only 1511% of annual precipitation were available. For the P, E and PE, the seasonal change was very obviously, from 1962 to 2009, the average value in summer were 4049 mm, 2399 mm and 2399 mm, accounted for 5594%, 5004% and 5594% to a year, respectively, and the proportion of 296%, 406% and 079%, respectively, in the winter. In the dry valley, atmospheric water decadal difference was very remarkable, the available of water resources was rich in the 1960s, relatively less in the 70s, gradually increased in the 80s and 90s, after entering this century appeared as reduced characteristic. In the dry valley, rainfall was likely to shift to reduced trend in the future and evaporation would remain the trend of increase, which make the amount of available water maintain the reduced trend, and the difficulty of water resources regulation would increase.〖JP〗〖HJ1〗〖HJ〗〖HQ〗