The main greenhouse gas emitted by human activities is carbon dioxide (CO2). This gas is primarily released through the burning of fossil fuels such as coal, oil, and natural gas for energy, transportation, and industrial processes. Deforestation also contributes to rising CO2 levels, as trees that absorb carbon are removed. Increased CO2 concentration leads to enhanced greenhouse effects, trapping heat in the atmosphere and contributing to global warming and climate change. Efforts to mitigate CO2 emissions include transitioning to renewable energy sources, improving energy efficiency, and enhancing carbon capture technologies to reduce overall greenhouse gas concentrations in the atmosphere.