- Greenhouse Effect: Caused by gases like CO₂, CH₄, N₂O, CFCs, and water vapour trapping heat in the atmosphere. - Acid Rain: Primarily caused by emissions of SO₂ and NOx, which form sulfuric and nitric acids in the atmosphere. - Ozone Layer Depletion: Caused by chemicals, particularly CFCs and halons, which release chlorine and bromine atoms that destroy stratospheric ozone molecules.