The world is running out of time to avert dangerous warming and keep the rise in global temperature below two degrees Celsius. Although scientists are still debating some specifics of climate change, such as whether warming has already caused Antarctica to lose mass, they clearly agree that global warming is real and that we humans are the culprit. In spite of this scientific consensus, some—including the U.S. president and many Republican representatives in Congress—continue to fiercely deny the existence of climate change and humanity's role in causing it. Their claims are misleading—they cite facts out of context, conjure up their own baseless theories about how the climate works or rely on conspiracy theories. Basic science and mountains of evidence, however, expose the flaws in their arguments. When the U.S. finally comes to terms with climate change, it will still need to decide the best way to cut carbon pollution—which Naomi Oreskes argues will ultimately depend on both the marketplace and government.