Damage to the ozone layer and the greenhouse effect are both caused by different things, and have different results. The greenhouse effect is caused by a build up of gases (notably carbon dioxide and methane, among others) in the atmosphere that prevent heat radiating from the planet’s surface out into space. This means that gradually more heat is retained by the atmosphere, leading to global warming. The ozone layer is damaged by gases such as Chloroflurocarbons (CFC’s) which thins the ozone layer, or causes it to disappear completely in places (over the poles, generally). The ozone layer prevents harmful ultra violet light from penetrating the atmosphere, so without it exposure to the sun leads to an increased risk of skin cancer, sunburn, etc.