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What is global warming?

What is global warming?

In its most commonly used sense, “global warming” refers to the gradual warming of global-average temperatures due to the slowly increasing concentrations of man-made atmospheric greenhouse gases, primarily carbon dioxide. But global warming can alternatively refer to simply the observation of warming, without iplying the cause(s) of that warming.

The burning of fossil fuels, mainly petroleum and coal, produces carbon dioxide as one of the by-products. As of 2010, the concentration of carbon dioxide is about 50% higher than it was before the start of the industrial revolution in the late 1800's. The potential warming effect of the extra CO2 is through its ability to absorb and emit infrared radiation, which is the type of radiation the Earth continually loses to outer space in response to heating by sunlight. This makes carbon dioxide a greenhouse gas, albeit a weaker one in the atmosphere than water vapor.

The net effect of greehouse gases on is to keep the lower layers of the atmosphere warmer that they otherwise would be without those gases. Therefore, it has seemed reasonable to assume that an increase in greenhouse gases would lead to warming.

But the big question is, how much warming?

How serious will global warming be? We don't know for sure, and there is much debate in the climate research community over this very question. The consensus of opinion is that a warming of about 0.2 degrees Celsius (about 0.4 deg. F) every 10 years is expected for the next 100 years or so.

The reason why there is so much uncertainty, though, is not because of the direct warming effects of more carbon dioixde, which are relatively weak. The main uncertainty is whether clouds and other components of the climate system will change in a way that amplifies -- or reduces -- the relatively weak warming effect of the extra carbon dioxide.


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