ABSTRACT Climate change is probably the greatest threat to global ecosystems that humanity has ever faced. Greenhouse gases, primarily from the production and combustion of fossil fuels for human energy needs, are heating up our atmosphere, changing our climate, and threatening the health and well‐being of people the world over. Predicted consequences of climate change include more frequent extreme weather events such as intensive precipitation, drought and floods, rising sea levels, increased smog in cities, and the possible spread of tropical diseases to more temperate climes. These grim effects can be limited if societies throughout the world act quickly to reduce greenhouse gas emissions. Substantially reducing emissions, however, means a fundamental shift in the way we produce and consume energy. To help bring about change, scientists, health professionals and nongovernment organizations such as the David Suzuki Foundation must work together to educate and motivate the public, industries, business organizations, and governments to take actions that will reduce the threat of global warming.