For over 30 years, I’ve been a climate scientist who has focused intensely on the causes and consequences of drought and climate change. I’ve done my research all over the planet, but my No. 1 focus has been on interactions of drought and climate change in the Southwest United States and on how drought and climate change are impacting the Colorado River. Seven states in the U.S. and Mexico depend on the Colorado River for water, yet I worry most about one state: Arizona.