Greenhouse Effect

Greenhouse Gases

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Our planet has existed for nearly 5 billion years, and throughout it's existence the atmosphere and climate have varied widely.  Evidence from the composition of volcanic gases suggest that the concentration of carbon dioxide in the earth's atmosphere was approximately 1000 times the concentration today.  Much of that carbon dioxide was dissolved into oceans and incorporated into rocks such as limestone, but the concentration that remained in the atmosphere made possible the most significant event in the history of our planet—life.  The ability of carbon dioxide to absorb heat kept the earth warm enough to permit life.  As early as 3 billion years ago, the oceans were filled with plants.  These plants were capable of photosynthesis.  Photosynthesis not only dramatically reduced the amount of carbon dioxide in the atmosphere, it increased the amount of oxygen.  The increase in oxygen made possible the evolution of animals, and thus, human life.

The composition of the earth's atmosphere is central to understanding why our planet is 35°C warmer than would be expected, due to it's frigid surroundings.  This results from two components of the atomosphere--water vapor and carbon dioxide.  These two compounds are responsible for maintaining a planet that is capable and warm enough to sustain life.

In 1860, John Tyndall experimentally demonstrated that carbon dioxide and water vapor absorb infrared heat radiation, and determined that these two atmospheric molecules, as a result, created a global warming effect.  Thanks to Tyndall, and the studies of many others after him, we now know that carbon dioxide and other greenhouse gases absorb heat, the concentration of carbon dioxide in the atmosphere, and the earth's average temperature has increased , but the question is: Are these items related?

Are Carbon Dioxide and Temperature Correlated?

Science has given us reliable evidence about the history of fluctuations in the earth's temperature.  Critical information about temperature fluctuations comes from the analysis of ice cores.  The Soviet drilling project at the Vostok Station in Antarctica has yielded over a mile of ice cores taken from the snows of 160 millennia.  The ratio of deuterium to hydrogen in the ice can be measured to estimate the temperature at the time the snow fell.  In addition, the tiny air bubbles in the ice can be analyzed for carbon dioxide and other gas concentrations.  The studies also show that temperature and carbon dioxide concentrations parallel each other.  When carbon dioxide concentrations were high the temperature was high.  One thing is clear:  The earth is a far different place today, than it was 130,000 years ago.