Scientists at the Southwest Research Institute in Boulder, Colorado have discovered signs of global warming on Mars. They can tell by viewing the volume and thickness of the ice in the polar caps.
The earth’s tilt has recorded variations known as Milankovitch cycles. These are also present on Mars, but to a degree that leads to greater variance in climate.
The Washington times has NASA’s explanation of how this difference affects Mars:
“On Earth, ice ages take hold when the polar regions and high latitudes become cooler than average for thousands of years, causing glaciers to grow toward the mid-latitudes,” said NASA. “In contrast, the Martian variety occurs when — as a result of the planet’s increased tilt — its poles become warmer than lower latitudes.” Water vapor moves toward the planet’s equator and forms ice and glaciers at mid-latitudes, said NASA.
The discovery of global warming on an unpopulated planet has sparked debate in the scientific community as to whether or not the sun has a greater effect on global temperatures than green-house gas emission.
In 2007, Russian physicist Habibullo Abdussamatov reported the Martian ice caps had been in decline for 3 years. He attributed this to the decline of solar irradiance.
While many scientists consider it to be a simple coincidence that Earth and Mars have shared a period between ice ages, Abdussamatov disagrees:
“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,” he told LiveScience in 2007.