People driving their cars, cranking on their air conditioners and switching on lights and dishwashers are responsible for most of the climate changes that are gradually drying up water supplies in arid and growing western states. This conclusion was led by researches and climate expert Tim P. Barnett at the Scripps Institution of Oceanography at the University of California, San Diego. The data was collected from 1950 through 1999. The researchers noted that winter precipitation falls increasingly as rain rather than snow and that snow melts faster. There are decreased river flows in summer months. The warming is aggravating dry summer conditions. Ultimately, they found that up to 60 percent of changes in river flow, temperature and snow pack between 1950 and 1999 can be attributed to human activities, such as driving, that release emissions including carbon dioxide and other greenhouse gases into the atmosphere.