There is a paradox at the heart of our changing climate. While the blanket of air close to the Earth’s surface is warming, most of the atmosphere above is becoming dramatically colder. The same gases that are warming the bottom few miles of air are cooling the much greater expanses above that stretch to the edge of space. This paradox has long been predicted by climate modelers, but only recently quantified in detail by satellite sensors. The new findings are providing a definitive confirmation on one important issue, but at the same time raising other questions. The good news for...