What is Global Dimming?

Climate change is a long-term shift in weather conditions identified by changes in temperature, precipitation, winds, and other indicators. The Climate is regulated by the balance between incoming and outgoing solar energy, which determines the Earth's energy balance. Global dimming is a cooling phenomenon.  

What is Global dimming?

The gradual reduction in the amount of global direct irradiance at the Earth's surface is called Global Dimming. It is believed that it has been caused by the increase in particulates such as sulphate aerosols in the atmosphere due to human action. In 1990s, there was a trend from Global dimming to Global brightening, when emission of the above particulates got reduce. It is the opposite of the Global warming because it produces cooling effects. It is considered as the actual effect of carbon emissions on global warming.

What are Carbon Footprint and Carbon Offsetting?

What causes of Global Dimming

1. Aerosols (colloid of fine solid particles or liquid droplets, in air or other gas) have been found to be the major cause of global dimming. Most aerosols in the atmosphere only scatter light from the sun, sending some of the sun's radiant energy back to space and exerting a cooling influence on Earth's climate.

2. Particle matters like sulphur dioxide, soot and ash (by-product of burning of fossil fuels by industry and internal combustion engines) enter the atmosphere and directly absorbs solar energy and reflects radiation back into the space, before it reaches the planet’s surface.

What are Carbon Cycle and Global Carbon Budget?

3. Water droplets containing airborne particles like sulphur dioxide, soot and ash (by-product of burning of fossil fuels by industry and internal combustion engines) form polluted clouds. These polluted clouds have heavier and larger number of droplets. These changed properties of the cloud – such clouds are called ‘brown clouds’ – makes them more reflective.

4. Vapours emitted from the planes flying high in the sky called contrails are another cause of heat reflection and related global dimming.

What are the effects of Global dimming?

Just like Global Warming, Global dimming has also withering effects on the atmospheric temperature of the earth as well as on the living beings.

1. It reduces the atmospheric temperature of the Earth. As a result, precipitation will be low that causes very low rainfall, which leads to droughts.

2. Pollutants and by-products cause thick fog, acid rain and pollution, causing many diseases such as respiratory diseases.

3. Cooling effects causes decline of vegetation, soil erosion etc.

Global dimming Vs Global warming

1. Global dimming is the reduction in heat or the reduction in the sun’s rays reaching the earth whereas Global Warming is the increase in Earth's mean surface temperature.

2. Global dimming covers the drastic effects of global warming.

Hence, we can say Global dimming and Global warming are dangerous and have fatal effects on our environment. It is very important to address them together because Global warming heat up the earth's atmosphere and Global dimming decreases the amount of solar radiation entering our planet.

Environment & Ecology: A Complete Study Material


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