A book chapter (about 9,000 words, plus references) presenting an act-consequentialist approach to the ethics of climate change. It begins with an overview of act consequentialism, including a description of the view’s principle of rightness (an act is right if and only if it maximizes the good) and a conception of the good focusing on the well-being of sentient creatures and rejecting temporal discounting. Objections to act consequentialism, and replies, are also considered. Next, the chapter briefly suggests that act consequentialism could reasonably be regarded as the default moral theory of climate change, in the sense that a broadly act-consequentialist framework often seems implicit in both scholarly and casual discussions of the ethics of climate change. The remainder of the chapter explores three possible responses to the threat of climate change: having fewer children to reduce the number of people emitting greenhouse gases; taxing greenhouse-gas (GHG) emissions (commonly called a “carbon tax”) to discourage GHG-emitting behavior; and reducing poverty to lessen personal, familial, and community vulnerability to the harms of climate change.