NASA geochemists have given climate sleuths a powerful new tool to study what heat-trapping carbon dioxide pollution may be doing to Earth's environment. It's a more accurate method for analyzing the carbon content of geological samples.
David Des Marais of the National Aeronautics and Space Administration's Ames Research Center in Mountain View, Calif., who developed the technique, has already used it to estimate much more accurately the rate at which the climate-regulating gas, carbon dioxide (CO2), flows naturally from the planet's interior.
This new estimate of natural CO2 release, Dr. Des Marais says, will enable other scientists to build more accurate computer models to study how the additional CO2 released by burning coal, oil, gas, and other human activity may affect climate.
In the atmosphere, CO2 absorbs infrared (heat) radiation coming from Earth's surface and thus tends to warm the planet. It's a key part of the atmosphere-ocean system that maintains a livable climate.
But man-made pollution now adds CO2 at a rate that could double the atmosphere's CO2 content over the next half century.
That could warm Earth by several degrees. Such warming might affect agriculture by changing rainfall patterns. It might also flood coastal areas if water from melting Antarctic ice raised sea level dozens of feet, as some climatic studies suggest. on also is a key element in the chemistry of organic life. Thus a more accurate method of analyzing carbon in geological samples and better insight into Earth's carbon dioxide cycle will help scientists study life's evolution.
The essence of the Des Marais method lies in cleaning carbon samples by burning them at 450 degrees C. Then the samples are melted by heating them to 1,200 degrees C. The carbon is converted to CO2, distilled from other gases, and measured.
This new process allows geochemists to purify and analyze the carbon without exposing it to air or other sources of contamination. Previous methods, using chemical cleaning, suffered from contamination which led to uncertainties.
By studying marine volcanic rock samples, Des Marais now estimates sea-floor volcanoes, which produce 90 percent of the outflow, release 30 million to 35 million tons of carbon (in the form of CO2) annually. Another 10 percent is released on land. Because of their inherent uncertainties, earlier estimates have ranged from one-tenth to ten times that rate. Human CO2 pollution, in contrast, releases something like 7 billion tons of carbon a year.
CO2 leaves the atmosphere as the oceans absorb it and living plants incorporate the carbon into their tissues. When marine plants die, settle to the bottom, and eventually become incorporated into rock, the carbon contained in their remains is locked away in the sea bed. That bed itself is not permanent.
New sea floor is formed as lava wells up along undersea ridges and moves slowly outward. Old sea bed plunges back into Earth's interior in deep undersea trenches. There is an endless cycle in which carbon released by volcanoes eventually returns to Earth's interior.
Thus, CO2 released naturally does not build up in the atmosphere. But, Des Marais notes, the processes that maintain this equilibrium operate on time scales of thousands and millions of years. Human activity upsets this equilibrium by increasing CO2 concentration 0.4 percent a year.
By helping to define the Earth's natural system with greater precision, Des Marais says his work will help scientists better understand the implications of CO2 pollution.