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http://www.nature.com/nsu/040517/040517-7.html
It's official: the world is getting darker. Scientists are now agreed that as cloud cover and particles in the atmosphere increase, the amount of radiation reaching us from the Sun is falling. And while some are nervous to raise the idea, they think the effect may help protect us from global warming. [continued]
Since the late 1950s, scientists have observed a 2-4% reduction in the amount of solar radiation reaching the Earth's surface,
Andre said:Since the late 1950s, I have observed a 2-4% increase in the amount of high cirrus type clouds generated by aircraft contrails.
Global dimming refers to the decrease in the amount of sunlight reaching the Earth's surface, caused by the presence of aerosol particles in the atmosphere that reflect and absorb light.
Global dimming can have negative impacts on human health, agriculture, and the environment. It can also affect the Earth's climate by altering the amount of solar radiation reaching the surface and potentially disrupting the water cycle.
Global dimming is measured using instruments such as pyranometers, which measure the amount of solar radiation reaching the Earth's surface, and sun photometers, which measure the amount of sunlight scattered by aerosol particles in the atmosphere.
The main sources of aerosol particles causing global dimming include human activities such as burning fossil fuels, biomass burning, and industrial processes. Natural sources like volcanic eruptions and dust storms also contribute to global dimming.
Global dimming can be reversed by reducing the emissions of aerosol particles into the atmosphere. However, this can also lead to an increase in global warming as the aerosols also have a cooling effect on the climate. Therefore, it is important to find a balance between reducing global dimming and mitigating the effects of global warming.