On Black Friday, while many Americans were shopping or sleeping off Thanksgiving, the federal government released the second volume of the congressionally mandated Fourth National Climate Assessment. This report reaffirms what the scientific community has long known: climate change is real, caused by humans and here now, Lab co-director Robert Kopp, director of the Director of the Rutgers Institute of Earth, Ocean & Atmospheric Sciences, writes in a guest column. Its impact on people and the environment grow more severe with every ton of greenhouse gas we emit into the atmosphere. But it's not too late to avoid the most detrimental effects of climate change if we get the planet on a course toward zero greenhouse gas emissions and take active measures to increase the resilience of at-risk communities and ecosystems.