CARBON DIOXIDE
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 interglacials.(http://www.nationmaster.com/encyclopedia/Carbon-dioxide)
ICE CORE RECORDS