Farther into the movie, Al explains the greenhouse gas effect. He presents a graphic that shows the sun’s rays heating the Earth’s surface resulting in infrared rays going from the Earth’s surface and back into space. His graphic suggests that some of the outgoing radiation is reflected from the top of the atmosphere and back to Earth. This idea is the basis of anthropogenic (man made) global warming theory. He fails to mention that this effect has never been measured, only calculated, and by scientists on one side of the debate. This is one of the most hotly debated issues in the global warming debate. Not only does this issue involve complicated theoretical quantum physics, but water vapor absorbs infrared radiation. As is often the case in global warming presentations, he forgets that water vapor is by far the most abundant greenhouse gas;3 to 4 percent of the atmosphere. And this is important because at most, man-made greenhouse gases are 1/ 10, 000 of Earth’s atmosphere.
With his description of greenhouse gases he presented a cartoon clip of the innocent sunrays being beaten up by the Greenhouse Gasses. But is water vapor really a bad thing?
Al also discusses the late Charles Keeling, a scientist who measured atmospheric carbon dioxide for many years. Al accurately describes how the amount of carbon dioxide in the atmosphere rises and falls with the seasons and why. He shows how Dr. Keeling measured a steady rise in carbon dioxide as the years went by, a trend often called the Keeling Curve. While some people still dispute the levels of man-made carbon dioxide in the atmosphere, I do not. For many years, carbon dioxide has been measured in many places and by many means;the results are almost identical in almost every instance. http://gaw.kishou.go.jp/wdcgg/PlotData.php
Next, Al gets right to business showing some of the worlds receding glaciers. According to the national Snow and Ice Data Center, most glaciers around the world are receding. But when you look at scientific studies on individual glaciers you begin to understand that temperature is not always the cause and that all of the glaciers that Al mentions have been retreating for over 100 years.
Let’s start with Al’s first example, Mt. Kilimanjaro. Al might be benefited by the knowledge that Kilimanjaro began receding in 1880 before CO2 began increasing in the atmosphere (Molg et al. 2003a). Also, local temperature records show that there have not been increasing temperatures in the last 100 years (King’uyu et al., 2000;Molg et al 2003, Hay et al., 2002). Additionally, the temperature on the mountain near the glaciers never gets above the freezing point (Georges and Kaser (2002). The glaciers on Kilimanjaro and other mountains in the area are shrinking due to a change in local precipitation. In 1880 the climate in the area changed from a very humid to a very dry climate resulting in less clouds and more direct sunlight. (Kaser et al. 2004).
Al’s second example is Grinnell Glacier in Glacier National Park. In this case, when you look at the pictures of receding glaciers, it is easy to say that a warming climate is causing the glacier to disappear. But like Kilimanjaro, these glaciers started melting over 100 years ago.