The greenhouse effect traps heat in the lower atmosphere due to gases like carbon dioxide, causing global warming and climate change over time. Burning fossil fuels is the primary cause of rising CO2 levels. Consequences of unchecked global warming include rising sea levels flooding coastlines, more extreme weather, and threats to food and natural resources. While some argue the causes and effects are uncertain, the document's authors believe global warming poses serious risks and requires action like transitioning to renewable energy and reducing greenhouse gas emissions.