BASIC BOOKS, APRIL 2014Earth is almost the perfect place for life as we know it to begin, prosper, and diversify. That makes it a very odd world. Most planets are too hot or too cold; too wet or too dry; too small or too big; or just plain wrong for life in any one of a hundred other ways.
One life-friendly property of Earth particularly intrigues me and compelled me to write my latest book, Lucky Planet—it has had a remarkably stable climatic history. Global average temperature is controlled by just three things: the brightness of its sun; the fraction of sunlight a planet reflects rather than absorbs; and the concentration of greenhouse gases in its atmosphere. This has been known for more than a century, but we have only recently realized that astronomical, geological, and biological processes have massively altered all three factors over the 4 billion years that life has existed on Earth. In that time our Sun has warmed 40 percent as it has aged; the Earth’s reflectivity has altered as clouds, ice caps, and continents have changed. And thanks largely ...
