Tuesday, September 14, 2010

Air dust and its climate impact

Most scientists agree that air dust has certain impact on our climate, but they still do not know how big this impact is. In order to put more light on this interesting topic scientists at The University of Alabama in Huntsville will spend the next three years studying the climate impacts of about 770 million tons of dust carried into the atmosphere every year from the Sahara.

As scientists pointed out some Saharan dust falls back to Earth before it leaves the Black continent, and the rest of the dust streams out over the Atlantic Ocean and/or Mediterranean Sea, where is carried on the wind all the way South America and the Southeastern United States. This dust has an as-yet unmeasured impact on Earth's climate by reflecting sunlight back into space.

Up to now there has been no facts, only assumptions about the impact of dust in the air on climate change, and scientists hope to change this by learning more about the characteristics of this dust, its concentrations in the atmosphere and its impact on the global energy budget.

Dust particles absorb some solar radiation, convert it to heat and release that heat into the air. Dust also reflects some radiation back into space, so it both heats and cools the atmosphere. Scientists are however much more interested about the impact dust has on heat energy in the air. Dust absorbs thermal energy rising from the ground and re-radiates it either toward space or back toward the surface.

This is the main reason why the scientists want to calculate how reflective dust really is. By calculating reflectivity scientists would be able to say with precision how much sunlight is being reflected, and thus they would be able to determine its impact on climate change.

Calculating this, however, will not be easy because the composition and shape of dust particles is very complex. With Saharan dust things are even worse because the composition of Saharan dust varies depending on which part of the Sahara the dust comes from, meaning that some dust absorbs more solar radiation, and some less.

The success of this study is therefore not guaranteed, but hopefully scientists will be able to at least somewhat determine the impact that dust in the air has on climate.

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