In an unprecendented move, Pope Francis issued a letter this morning to the Church's leadership acknowledging global warming as a human-caused phenomenon and imploring world leaders to take action to address it. It was the first encyclical—as such letters are known—of Francis's papacy, and the first papal encyclical in the history of the Catholic Church to focus on the environment . In the 184-page encyclical, the leader of 1.2 billion Catholics worldwide frames the environmental crisis as a potentially cataclysmic situation in need of an immediate global solution. Francis not only remarks that “the earth, our home, is beginning to look more and more like an immense pile of filth," but also warns of “grave consequences for all of us” if we fail to act on climate change. 3435 Pope Francis, who studied chemistry in Buenos Aires before entering the seminary, writes that a “very solid” scientific consensus has formed about the causes of climate change. “A...