The new technique developed by Dr. Roy Spencer and Dr. Danny Braswell, both research scientists in the Earth System Science Center at The University of Alabama in Huntsville, uses microwave sensors on NOAA and NASA satellites to collect surface temperature data over virtually all of Earth's land area.
They say they hope the new system will provide a stable method for monitoring climate change without some of the problems associated with the existing network of surface thermometers.
The new method was presented at the recent Fourth International Conference on Climate Change in Chicago.
While satellite sensors have been used for years to collect temperature data from the ocean surface and in the deep layers of the atmosphere, problems with interpreting the data have prevented their use in collecting surface temperature data over land areas.
"The problem has always been that land background is quite variable, which makes it very difficult to model," explained Spencer.
Due to differences in their microwave emissions, a forest at 70 degrees F and a sandy desert at 70 degrees F look different to the satellite instruments. That makes it difficult to interpret what the instrument is seeing, which has kept researchers from using microwave sensors to measure temperatures over land.
Spencer and Braswell claim to have solved the problem by dividing Earth's land surface into ten basic microwave surface types, ranging from swampy wetland to arid desert. By knowing the mix of land types in each area scanned by the sensor, they can more accurately estimate temperatures for that area.
One of the biggest advantages of the satellite-based monitoring is its coverage. The satellite sensors collect temperature data over more than 95 percent of the Earth¹s land area. Credible surface temperature data are not otherwise available over much of the Earth, including portions of Russia and Siberia, Australia, South America, Northern Canada and most of both Africa and the Antarctic.
One of the biggest shortcomings of the satellite-based dataset is its relative brevity: The best satellite microwave sensor data used by Spencer and Braswell goes back only to 2002, although previous sensors might allow temperature data to be collected back to 1987.
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