What are CO2 equivalents?

We use CO2 equivalents to collectively express the human impact on the atmosphere and make it tangible and calculable. But CO2 is not the only gas that is emitted in large quantities by our activities and affects the climate. Methane, for example, is another gas that is released in excessive quantities by human activity. 1g of methane is about 25 times more climate-impacting than 1g of CO2. So 1g of methane adds up to 25g of CO2 equivalent.