1"As the light enters the atmosphere, some of it is scattered by air molecules or reflected from white clouds back into space. Since air is mostly transparent to visible light, much of the light that isn't reflected back into space goes through the atmosphere to Earth's surface". 2"Some of the light that makes it to the surface is also reflected back into space However, since the average albedo of Earth's surface is around 15%, most of the light that makes it to the surfaces is absorbed, warming our p
lanet." Overall, slightly less than half of the the sunlight at the top of our atmosphere is absorbed by Earth's surface. Because there are natural sources of the various GHGs, the concentrations of these gases have fluctuated all throughout Earth's history. 2''However, human activities, especially ones associated with the industrial revolution, have increased anthropogenic emissions of several important GHGs dramatically since the mid 1800s." Various human activities have altered the natural mix of a broad range of gases that play a role in determining climate. Our focus here, however, will be on alterations in carbon dioxide and methane levels since pre-industrial times. 1"The effects of global warming are being felt around the world and unless international efforts are launched within the next 10 years, species will disappear and the Earth will be a vastly less habitable planet by the end of the century, according to NASA scien
tist James E. Hansen.''
lanet." Overall, slightly less than half of the the sunlight at the top of our atmosphere is absorbed by Earth's surface. Because there are natural sources of the various GHGs, the concentrations of these gases have fluctuated all throughout Earth's history. 2''However, human activities, especially ones associated with the industrial revolution, have increased anthropogenic emissions of several important GHGs dramatically since the mid 1800s." Various human activities have altered the natural mix of a broad range of gases that play a role in determining climate. Our focus here, however, will be on alterations in carbon dioxide and methane levels since pre-industrial times. 1"The effects of global warming are being felt around the world and unless international efforts are launched within the next 10 years, species will disappear and the Earth will be a vastly less habitable planet by the end of the century, according to NASA scien
tist James E. Hansen.''bibliography
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