New York Times: AMONG environmental activists, the international market for carbon credits is often compared to the medieval sale of indulgences. Pope Francis presides over the Roman Catholic church, the institution that created the market for indulgences, so you might expect him to be more sympathetic on this issue. And yet his recent encyclical Laudato Si, while forcefully urging action to combat climate change, specifically criticizes the sale of carbon credits. The pope claims that the environment cannot...