Carbon dioxide (CO2) is primarily responsible for global warming. It is released through various human activities, including the burning of fossil fuels such as coal, oil, and natural gas, as well as deforestation and industrial processes. While there are other greenhouse gases like methane and nitrous oxide, CO2 remains the most significant due to its abundance and long-lasting presence in the atmosphere. The increase in atmospheric CO2 levels leads to heat retention, contributing to climate change impacts such as rising sea levels, extreme weather events, and shifts in ecosystems, making it a key focus for environmental policy and climate action.