As you argue in your main leader and briefing on the surprising fall in the fertility rate in less developed countries, the new demographic trend is likely to bring big benefits (“Falling Fertility” and “Go Forth and Multiply a Lot Less,” October 31, 2009). Although the world population is still growing, it is growing at an ever-slower rate. This was expected, but the fall in the fertility rate is so pronounced that it explains your enthusiasm. In your words, “it carries a lesson about how to solve the problems of climate change.” As population growth is one of the main drivers of climate change, this is indeed the case. But it is not clear what this “lesson” of yours actually entails. That less people means less climate change? Or that problems tend to solve themselves? Mind you, many processes associated with climate change, such as the melting of polar ice or the decline in biodiversity, cannot be stopped or reversed even if the world’s population stops growing today. To wit, you are offering false hope on climate change. There will be no surprises in solving its problems.