As global warming became a cause of concern in the 1980s, researchers and climate activists initially paid little attention to the possible health effects of a warmer world. This changed quickly between 1985 and 1989, when scientists working on contracts with the US Department of Energy and the Environmental Protection Agency extrapolated from existing knowledge about the impact of weather on health to speculate about how global warming would impact health. However, they downplayed the impact of their contributions by highlighting the uncertainty in their models and the adaptability of human societies. Since that time, physicians and other health scientists have maintained a steady drumbeat of warnings about the health effects of global warming. They have published widely in the medical literature and participated actively in international scientific collaborations. Their research has significantly increased the breadth and depth of climate-health science and shown that measurable impacts of global warming have already begun. But as the many climate crises of 2023 show, action against global warming remains inadequate. Is it still reasonable to hope that health advocacy will incite communities and politicians to act? The history of climate and health advocacy reveals many obstacles that must be overcome.