Though there has been a fair amount of evidence that the Earth’s atmosphere is
undergoing global warming, the process is slow enough that there are plenty of
skeptics, including some very influential people, who argue that it may not be
happening at all.

Global climate change does occur, however, and sometimes so quickly that you can
watch it happening. Just look at our neighbor, Mars: within the last month, the global
atmospheric temperature of Mars has increased by approximately 50 degrees
Fahrenheit, according to data being received by the Thermal Emission Spectrometer
(TES) on NASA’s Mars Global Surveyor spacecraft.

The cause of this sudden shift is a giant dust storm that has snowballed and now has
enveloped almost the entire planet, absorbing a lot of the Sun’s energy in the upper

“It started out as a large dust storm in the southern latitudes in late June,” said Arizona
State University’s Korrick Professor of Geology Philip Christensen, the principal
investigator for TES. “The dust trapped sunlight and heated the atmosphere locally. As
this warm air flowed to regions where the air was still cool it generated winds which
raised more dust into the atmosphere.

“By the end of the first week in July, most of the planet was enveloped and our
readings of atmospheric temperature had increased by about 30 degrees

TES is an instrument designed to take detailed readings of energy emissions in the
infrared range (heat energy) to aid in studying Mars’ geology and atmosphere. A movie
showing the instrument’s readings over the last month, tracking the expanding dust
storm and the accompanying increase in atmospheric temperature, is available on
the web at: Curiously, just as Earth’s global warming may
theoretically cause the opposite thermal effect on some parts of the planet, so Mars’
current heat wave is likely to bring on a big chill further on down the road.

“In the end, the cloaking of the entire planet with dust is probably going to cool down
the surface of Mars significantly and ultimately shut this entire weather system down
again,” said Christensen. “It’s kind of like what we imagine would happen with a
nuclear winter on Earth.” In fact, Christensen points out, it was another global dust
storm observed on Mars in the early 1970’s that gave astronomer Carl Sagan and
others the idea of the kind of catastrophic climate change that might be caused by a
global nuclear war.

“Mars’ atmosphere is a much simpler system than Earth’s,” Christensen cautions,
“since it is much thinner and lacks most of the water that we have in ours, trapping
energy and moderating changes. “Still, it provides us with an interesting model for
how global climate changes can occur, albeit much more quickly than on our planet.
Nonetheless, some large scale changes here could be abrupt as well.”


A NASA/JPL press release on the current martian dust storm is available at: .