Greenhouse JXUwMDNmJXUwMDA2JXUwMDEyJXUwMDE2JXUwMDE2 are chemical compounds in the atmosphere that trap heat there. They retain a proportion of the sun's heat through a mechanism known as the JXUwMDNmJXUwMDE1JXUwMDE3JXUwMDAwJXUwMDBiJXUwMDA2JXUwMDA3JXUwMDFhJXUwMDA2JXUw MDE2 effect . Greenhouse gases, mainly JXUwMDNiJXUwMDAyJXUwMDEzJXUwMDEwJXUwMDBkJXUwMDAx JXUwMDNjJXUwMDBkJXUwMDA2JXUwMDE3JXUwMDExJXUwMDBkJXUwMDAx (CO2), are naturally present in the atmosphere in small quantities (less than 1%).

Pollution is due the presence of too much JXUwMDNiJXUwMDAyJXUwMDEzJXUwMDEwJXUwMDBkJXUwMDAx JXUwMDNjJXUwMDBkJXUwMDA2JXUwMDE3JXUwMDExJXUwMDBkJXUwMDAx in the atmosphere due to too much JXUwMDNlJXUwMDA5JXUwMDFjJXUwMDAwJXUwMDFhJXUwMDA1 JXUwMDNlJXUwMDEzJXUwMDEwJXUwMDA5 burning.

If nothing is done, the JXUwMDM1JXUwMDA4JXUwMDA5JXUwMDE4JXUwMDFkJXUwMDA3JXUwMDA5 of Polar ice-caps may cause the JXUwMDJhJXUwMDFiJXUwMDFhJXUwMDE2 of sea levels. The climate is also affected, there will be more JXUwMDJkJXUwMDFiJXUwMDFlJXUwMDAyJXUwMDE3JXUwMDAxJXUwMDBkJXUwMDBhJXUwMDE3JXUw MDE1JXUwMDAzJXUwMDBlJXUwMDA5 weather conditions such as devastating JXUwMDMwJXUwMDFkJXUwMDA3JXUwMDAwJXUwMDFiJXUwMDBhJXUwMDAyJXUwMDBmJXUwMDBiJXUw MDE2JXUwMDVm torrential JXUwMDJhJXUwMDEzJXUwMDA4JXUwMDA3JXUwMDFk causing catastrophic JXUwMDNlJXUwMDBhJXUwMDAzJXUwMDAwJXUwMDBiJXUwMDE3 or severe and longer-lasting JXUwMDNjJXUwMDE2JXUwMDFkJXUwMDFhJXUwMDEyJXUwMDBmJXUwMDFjJXUwMDA3 .

It may also cause the erosion of JXUwMDNiJXUwMDBjJXUwMDBlJXUwMDEyJXUwMDA3JXUwMDE1JXUwMDBk zones and desertification, forcing populations to JXUwMDM1JXUwMDA0JXUwMDBlJXUwMDE1JXUwMDEzJXUwMDE1JXUwMDEx because of food or water JXUwMDJiJXUwMDFiJXUwMDA3JXUwMDFkJXUwMDA2JXUwMDE1JXUwMDA2JXUwMDAyJXUwMDE2 , causing famine because of JXUwMDNiJXUwMDExJXUwMDFkJXUwMDFm JXUwMDNlJXUwMDA3JXUwMDA4JXUwMDA1JXUwMDE5JXUwMDA3JXUwMDE3JXUwMDE2 and even worse this may lead to the proliferation of JXUwMDNjJXUwMDBkJXUwMDFhJXUwMDE2JXUwMDA0JXUwMDEyJXUwMDE2JXUwMDE2 .