Abstract:
The concentration of several greenhouse gases has increased over time. Human activity increases the greenhouse gases effect primarily through release of carbon dioxide, but human influences on other greenhouse gases is also important. The ongoing accumulation of greenhouse gases causes increasing global warming. The recent IPCC 2007 shows that global average air temperature near Earth's surface rose to 0.74 ± 0.18°C in the last century and report concluded "most of the observed increase in globally averaged temperatures since mid-20th century is very likely due to the observed increase in the concentration of anthropogenic greenhouse gases". Trends of increase in temperature and changes in precipitation over India/Indian sub-continent with global trends are compared. It is found that the changes in temperature in India/ Indian-subcontinent over last century are broadly consistent with global trend of increase in temperature. Global climatic changes will have major effects on precipitation, evapotranspiration, and runoff. But estimating the nature, timing, and even the direction of the impacts at the regional and local scales of primary interest to water planners involve many uncertainties. This paper presents a status of the studies carried out in context of impact of climate change on Himalayan water resources. An overview of the global warming and climate change along with observed and projected scenarios has been presented. Some studies have been carried out to understand input of climate change on water availability for few Himalayan basins. It is found that some preliminary results related to influence of climate change on water availability for few Himalayan basins are available. There is a need to standardize the projected future climatic scenarios for different Himalayan basins and to study the impact of those scenarios on the water availability. An understanding of hydrological response of a river basin under changed climatic conditions would help in solving potential water resources problems associated with floods, droughts and availability of water for agriculture, industry, hydropower generation, domestic and industrial use.
