Hansen wrote this book because of his concerns about the future world his grandchildren would inhabit. He shares basic physics explanations, as well as his thoughts about possible future climate issues. After decades of studying the physics of our atmosphere and greenhouse gases, he is certain that we are facing radical environmental changes in the immediate future. He holds degrees in Mathematics, Astronomy, and Physics, and began his career analyzing the atmosphere of Venus for NASA. Following that work he shifted to studying the atmosphere of Earth and the greenhouse effect.