Western US Entering Worst Drought <br />in 1,200 Years, Study Says The study from Columbia University used tree ring data and climate models. The information let them measure moisture changes <br />dating back to a big drought in the late 800s. Since then, they discovered there were <br />three more periods of "extreme dryness" after that. Lead author Park Williams, via CBS News Over the last two decades, the <br />west has been mired in one of <br />its most drier periods. In that time, climate change has increased temperatures by <br />2.2 degrees Fahrenheit. The study adds that the modern drought will affect a <br />wider area due to the warming climate. Researchers add that its fast pace is <br />half due to human-caused climate change. Lead author Park Williams, via CBS News
