The primary gas responsible for the greenhouse effect is carbon dioxide (CO2). While other gases such as methane and nitrous oxide also contribute to the greenhouse effect, CO2 is the most significant due to human activity such as burning fossil fuels and deforestation. Its ability to trap heat in the atmosphere leads to the warming of the planet, contributing to climate change. Efforts to reduce CO2 emissions are crucial in addressing global warming and its impacts on ecosystems and weather patterns.