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A minor but very important component of the atmosphere, carbon dioxide traps
infrared radiation. Atmospheric CO2 has increased about 25 percent since the
early 1800s, with an estimated increase of 10 percent since 1958 (burning
fossil fuels is the leading cause of increased CO2, deforestation the second
major cause). The increased amounts of CO2 in the atmosphere enhance the
greenhouse effect, blocking heat from escaping into space and contributing to
the warming of Earth's lower atmosphere. (Earth Observatory)
The most direct method for measuring atmospheric carbon dioxide concentrations
for periods before direct sampling is to measure bubbles of air (fluid or gas
inclusions) trapped in the Antarctic or Greenland ice caps. The most widely
accepted of such studies come from a variety of Antarctic cores and indicate
that atmospheric CO2 levels were about 260¿280uL/L immediately before
industrial emissions began and did not vary much from this level during the
preceding 10,000 years.
The longest ice core record comes from Vostok, Antarctica, where ice has been
sampled to a depth of 3,600 meters, corresponding to an age of 420,000 years
before the present. During this time, the atmospheric carbon dioxide
concentration has varied between 180¿210 uL/L during ice ages, increasing to
280¿300 uL/L during warmer
From: NASA Earth Observatory Glossary:
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