The debate over the existence of global warming and climate change has been muddled because of satellite data showing a cooling trend in Earth's troposphere. This apparent cooling is in disagreement with measurements at surface stations and with climate models. In their Perspective, Hansen et al . discuss a correction to the satellite data published by Wentz and Schabel in Nature that may have profound implications for discussions of climate change. Wentz and Schabel discovered that the original satellite data, published in 1995, was not adjusted for the natural decay of spacecraft altitude caused by atmospheric drag. When this adjustment is made, the satellite data agree with both surface data and model calculations. The authors of the Perspective conclude that the question now is not whether global warming exists--it clearly does--but what should be done about it.