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Global warming: The probable cause

Hal Sundin
Post Independent
Glenwood Springs, CO Colorado
As I See It
ALL |

The decline of the snowfield and disappearance of the glacier in the cirque below Castle Peak in just 40 years is telling evidence of the rapid pace of global warming. In the early 1970s, there was a temporary rope tow that provided summer skiing on the extensive snowfield above the Montezuma mine.

When I climbed Castle Peak in late August of 1983, the rope tow was no longer there, but people were hiking up and skiing down the snowfield. In mid-September of 1992, the snowfield was no longer skiable, but there was enough of it remaining to ascend and descend on, which was far preferable to the alternative of scrambling over boulders and loose talus. Ten years later, the snowfield had shrunk drastically, exposing the lower end of the glacial remnant which had been there since the last ice age. And in August of this summer there was very little snow left and the glacier was gone, leaving only a depression in the talus with a little water in it.

So what is the most likely cause of this sudden warming? Some are quick to point out that the Earth has long been subject to both warming and cooling trends, as evidenced by the four glacial periods and four warmer interglacial periods of the last million years. Scientists are not certain of the exact cause of those temperature changes, but they may be due to fluctuations in solar radiation or perturbations in the Earth’s orbit. However those effects are far more gradual than what is taking place today.



So we have to look for another explanation for the current rapid warming trend. Global temperatures have risen by 1.5 degrees Fahrenheit in just 100 years, and two-thirds of that increase has taken place since 1980. The most logical explanation is the amount of greenhouse gasses, primarily carbon dioxide, in the atmosphere. Greenhouse gasses reduce the amount of solar energy reflected back into space, and an increase in those gases will alter the natural balance. Carbon dioxide levels in the atmosphere have increased by 30 percent in the past 100 years as the burning of fossil fuels has skyrocketed, and is now at the highest level in nearly a million years.

That the 30 percent increase in the last 100 years is due to our burning of fossil fuels is convincingly confirmed by the changes in the chemical composition of the atmosphere during that time. Computer analyses show both that the increase in carbon dioxide matches very closely the amount of carbon in the fossil fuels we have burned, and also that there has been a reduction in atmospheric oxygen equal to the amount that would be consumed in the burning of that amount of fossil fuels.



Another piece of evidence is the 30 percent reduction in the proportion of radioactive carbon14 which has taken place in atmospheric carbon dioxide. This is because carbon of fossil-fuel age is devoid of carbon14, so when fossil fuels are burned, the carbon dioxide entering the atmosphere from that source has reduced the concentration of carbon14 found in atmospheric carbon dioxide by an amount consistent with the amount of fossil fuels which have been burned.

It is these facts that have convinced the overwhelming majority of scientists on the International Panel on Climate Change to conclude that human activities (primarily burning fossil fuels) are very likely the cause of global warming, and the Meteorological Society to warn Congress that the buildup of greenhouse gasses (primarily carbon dioxide) is a serious threat to our future. The evidence that carbon dioxide is the main cause of global warming is too convincing to ignore, and those who deny that evidence are making a spectacle of their ignorance.

Next time, the 2010 election; then back to global warming and its potential effects.

– Glenwood Springs resident Hal Sundin’s column runs every other Thursday in the Post Independent


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