Global Dimming is a phenomenon where there is a gradual reduction in the amount of direct irradiance at the surface of the earth. This happens when some particles in the air absorb the natural light of the sun and reflect it back. The effect of this is different at different places on the earth.
It is said to have been caused because of the increase in sulfate aerosols in the environment due to activities conducted by the humans. It has caused a huge interference in the hydrological cycle by reducing the evaporation and has also led to severe decrease in the rainfall in some areas. It also causes a cooling effect which partially counter reacts with global warming.
Below given are some main causes of Global dimming:
Causes
- The increase in the presence of aerosol particles in the atmosphere. These particles absorb solar energy and reflect the light back into space. The pollutant particles can also form themselves into nuclei for cloud droplets. Increase in pollution in return further form clouds which become more reflective, blocking the sunlight. These clouds also result in decrease in rainfall.
- Clouds form interception of heat and sun which gets radiated from the earth. The effects of these vary in time and location and this phenomenon, if happened in day time gives a cooling effect but the effect at night is reverse.
- The incomplete combustion of fossil fuels like diesel and wood causes releasing of black carbon particles in the air which in turn has a major effect in the heating up of the atmosphere and it dims the surface of the seas and oceans as these particles absorb solar radiation and throw it back.
- Other unknown particles of pollution also absorb the natural sunlight and throw it back, causing the reduction in sunlight which reaches on the earth.
Effects
- There is around 10% reduction in the sunlight when it tries to each the surface area of the earth because of the pollution clouds which contain black carbon in high amounts.
- There are also many regional effects of this phenomenon which include warming of most of the places on earth whereas the places which are downwind from air pollution generally stay cool.
- Black carbon is secondary to Carbon Dioxide and hence it indeed increases global warming. The particles of black carbon which absorb sunlight would transfer that solar energy to the colder parts of the earth like the Himalayas and the Alps, causing the melting og glaciers and increase in the water levels of the earth.
- The vapour trails of aircrafts are implicated when global dimming takes place and if this phenomenon increases beyond limits; civil air traffic needs to be shut down completely.
Hence, we learn that the phenomena of global dimming can be controlled if the emission of black carbon and other harmful particles in the air is controlled. The above given points tell you about the basic information about global dimming, its causes and effects.
