Climate change is not a vague possibility for the distant future. It is already affecting the planet - more-intense storms or longer-lasting droughts, longer and hotter heat waves, or more rain. Careful scientific observations confirm climate change is happening, here and now. It is only natural to ask if global warming caused Hurricane Sandy, the superstorm that ravaged the East Coast in 2012, or is global warming responsible for the recent wildfires in California, Colorado or Texas? Catherine Gautier is professor emeritus, Geography Department, University of California, Santa Barbara. Richard C.J. Somerville is a distinguished professor emeritus, Scripps Institution of Oceanography at UC San Diego.