Instruments, Locations Key To Greenhouse Gas Measure
By WeatherBug Sr. Meteorologist, James West
The measurement of greenhouse gases, including carbon dioxide and methane, requires delicate, precise instruments and for baseline measurements, remote locations.
The National Oceanic and Atmospheric Administration maintains four sites around the world. They are located atop Mauna Loa in Hawaii, at the South Pole, and in Barrow, Alaska, and the American Samoa. These stations remoteness allow them to measure greenhouse gases unencumbered by local sources.
The diversity of the locations -- two tropical, two polar -- and the hemispheric spread --two south and two north of the equator-- help detect variations in climate zones and the hemispheric differences due to more landmass north and more ocean south of the equator. Combined, this gives them baseline measurements that better represent regional and even global values, not local values.
The measurement of carbon dioxide at these locations is done using precise instruments calibrated frequently by leading scientists using exacting protocol. The instrumentation accuracy, using independent test, are estimated to be better than 0.2 part per million (ppm).
The common greenhouse gas detection instrument slowly pumps atmospheric gas into a small chamber. A beam of infrared energy is transmitted into the chamber and the carbon dioxide absorbs this infrared energy. Another instrument detects the remaining infrared energy in the beam and the carbon dioxide is calculated based on the drop in this energy. Some systems remove water vapor before measurement, while others use a water vapor correction in their carbon dioxide measurements.
Earth Networks, the parent company of WeatherBug, has launched its own worldwide greenhouse gas measurement network. Fifty of the sensors will be installed across the U.S., and another 50 located around the world, with rollout completed by middle 2012. This network will supplement the government network and allow scientist a finer grid of data. Read more about the network at: Earth Networks website
Source: NOAA, Earth System Research Laboratory, Earth Networks
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