Satellites Show Earth Has A Fever

By Roland Piquepaille

A recent study from NASA says that satellites are acting as thermometers in space. Contrary to meteorological ground stations which measure the air temperature around two meters above the ground, satellites can accurately measure the temperature of the Earth's skin. And this new study, which covers the 18-year period going from 1981 to 1998, shows that the Earth's temperature is rising 0.43°C per decade instead of the O.34°C found by previous methods. Unfortunately for us, if satellites can more precisely measure this rise of the Earth's temperature, they cannot cure this fever.

For the first time, satellites have been used to develop an 18- year record (1981-1998) of global land surface temperatures. The record provides additional proof that Earth's snow-free land surfaces have, on average, warmed during this time period, according to a NASA study. The satellite record is more detailed and comprehensive than previously available ground measurements. The satellite data will be necessary to improve climate analyses and computer modeling.

Menglin Jin, the lead author, commented until now global land surface temperatures used in climate change studies were derived from thousands of on-the- ground World Meteorological Organization (WMO) stations located around the world, a relatively sparse set of readings given Earth's size. These stations actually measure surface air temperature at two to three meters above land, instead of skin temperatures. The satellite skin temperature dataset is a good complement to the traditional ways of measuring temperatures.

So, what are the results?

Inter-annually, the 18-year Pathfinder data in this study showed global average temperature increases of 0.43 Celsius (C) (0.77 Fahrenheit (F)) per decade. By comparison, ground station data (2 meter surface air temperatures) showed a rise of 0.34 degrees C (0.61 degrees F) per decade, and a National Center for Environmental Prediction reanalysis of land surface skin temperature showed a similar increasing trend in global and land surface temperature, in this case 0.28 degrees C (0.5 degrees F) per decade.

Now, these scientists want to extend this 18-year period of observation up to now. And you can see the results below, during the European heat wave of the summer of 2003.

This image shows the differences in daytime land surface temperatures collected between July 2001 and July 2003. A blanket of deep red across southern and eastern France shows where temperatures were 10 degrees Celsius (18 degrees Fahrenheit) hotter during the summer of 2003 (Credit: NASA).

You can find other spectacular images on this page at the Goddard Space Flight Center.

Source: NASA/Goddard Space Flight Center news releas, April 22, 2004; via EurekAlert!