Simultaneous warming on Earth and Mars suggests that our planet's recent climate changes have a naturaland not a human- inducedcause, according to one scientist's controversial theory.
Earth is currently experiencing rapid warming, which the vast majority of climate scientists says is due to humans pumping huge amounts of greenhouse gases into the atmosphere. (Get an overview: "Global Warming Fast Facts".)
Mars, too, appears to be enjoying more mild and balmy temperatures.
In 2005 data from NASA's Mars Global Surveyor and Odyssey missions revealed that the carbon dioxide "ice caps" near Mars's south pole had been diminishing for three summers in a row.
Habibullo Abdussamatov, head of the St. Petersburg's Pulkovo Astronomical Observatory in Russia, says the Mars data is evidence that the current global warming on Earth is being caused by changes in the sun.
"The long-term increase in solar irradiance is heating both Earth and Mars," he said.
Solar Cycles
Abdussamatov believes that changes in the sun's heat output can account for almost all the climate changes we see on both planets.
Mars and Earth, for instance, have experienced periodic ice ages throughout their histories.
"Man-made greenhouse warming has made a small contribution to the warming seen on Earth in recent years, but it cannot compete with the increase in solar irradiance," Abdussamatov said.
By studying fluctuations in the warmth of the sun, Abdussamatov believes he can see a pattern that fits with the ups and downs in climate we see on Earth and Mars.
Abdussamatov's work, however, has not been well received by other climate scientists.