Final answer:
Chlorofluorocarbons (CFCs) are the only greenhouse gas produced solely by human activities, as they have no natural sources and are entirely synthetic. Other greenhouse gases like methane, nitrous oxide, and carbon dioxide have both natural and anthropogenic sources. Fluorinated gases are also synthetic and only produced by humans, with significant environmental impacts. chlorofluorocarbons
Step-by-step explanation:
Among the greenhouse gases produced only by humans, chlorofluorocarbons (CFCs) are unique because they have no natural sources and are entirely synthetic. These gases were created for use in industries such as refrigeration and aerosol propellants but have been phased out due to their harmful effect on the ozone layer and their contribution to climate change.
While other greenhouse gases like methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) are also emitted in substantial amounts due to human activities, they are naturally occurring in the environment as well. Methane is produced both naturally and by human activities such as agriculture and fossil fuel extraction, and nitrous oxide is a part of the Earth's nitrogen cycle while also being emitted through agricultural and industrial activities. Carbon dioxide, the primary greenhouse gas affecting climate change, is emitted in large quantities from natural processes like respiration and volcanic eruptions, as well as from human-induced sources like burning fossil fuels and deforestation.
Fluorinated gases, which include Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), and Sulfur Hexafluoride (SF6), also have no natural sources and like CFCs are only produced by human activities. They have been used as substitutes for CFCs but have their own negative environmental impacts due to their long atmospheric lifetimes and high global warming potential (GWP).