A greenhouse gas (GHG) is a gas that causes the atmosphere to warm by absorbing and emitting radiant energy. Greenhouse gases absorb radiation that is radiated by Earth, preventing this heat from escaping to space. Carbon dioxide (CO₂) is the most well-known greenhouse gas, but there are others including methane, nitrous oxide, as well as water vapor among others. Human-made emissions of greenhouse gases from burning fossil fuels as well as industry, and agriculture are the leading cause of global climate change. Before the Industrial Revolution started in the mid-1700s the atmosphere contained approx. 280 particles of carbon dioxide per 1 million particles (280 ppm CO2). Human activities led to an increase up to 417 ppm CO2 in 2022.
