Veerabhadran Ramanathan recaps 35 years of key findings, and brings his audience up to date on the latest climate data, models, and observations which together demonstrate how CO2 is but one piece of a complex puzzle. Ramanathan deploys simple but extremely helpful metaphors to describe the processes behind warming. CO2 in the atmosphere, whether manmade or natural, surrounds the earth like a blanket, holding onto the radiation from the sun. When the blanket is behaving properly, enough sun’s heat stays on earth to keep biological forces humming, and the rest escapes back into space. But if this blanket gets thicker, it “prevents the body from losing heat.” CO2 is particularly noxious, since it “lives in the atmosphere for a century if not longer.” But it turns out we have other molecules circling the globe to worry about. Starting in the 1970s, scientists discovered that compounds in the atmosphere, such as chlorofluorocarbons and methane, acted more powerfully than CO2 in making our “blanket” more efficient in trapping heat. They began developing models trying to describe the complex interplay of heat-trapping gases with earth’s natural climate systems. Ramanathan’s work, which involves precise observations from the surface, satellite measurements, balloons and unmanned vehicles, has convinced him “that climate change is worse than what we get from the models.” The most recent UN report on climate change predicts that greenhouse gases already in circulation have committed the planet to a warming of 2.5 degrees. “No matter what we do today to reduce emissions, the planet will still heat up,” says Ramanathan. But, through a quirk that Ramanathan has spent 10 years uncovering, the planet actually manifests only ¼ of the warming it should based on these climate models. Air pollution, specifically brown clouds from burning biomass, Ramanathan has learned, act as a global warming mask, reducing sunlight on the ground. “On the one hand, it has protected us, but als...