An environmental phenomena marked by darker, polluted clouds that causes more of the sun’s heat and light to be reflected back into space. Fossil fuel use produces airborne pollutants such as soot, ash and sulphur dioxide. Polluted air results in clouds with larger number of droplets than unpolluted clouds. This then makes those clouds more reflective. More of the sun’s heat and energy is therefore reflected back into space. Climatologists studying global dimming believe that the reflection of heat have made waters in the northern hemisphere cooler. As a result, less rain has formed in key areas and crucial rainfall has failed to arrive over the Sahel in Northern Africa.