Dwindling Ice Covers Boost Global Warming

Decades ago, when the first climate models appeared, they showed that diminishing ice and snow covers would contribute to exacerbating the effects of global warming. A new study shows that this is happening at a much more intense level than originally calculated.

Over the past 30 years or so, the amount of ice- and snow-covered surfaces on Earth has decreased considerably, which means that less solar radiation is emitted back into space from these areas.

As such, the world is getting warmer. The effects of the excess Sun-generated heat trapped in the atmosphere are added to those produced by human-generated greenhouse gases and aerosols.

These phenomena are self-sustaining, and also support each other. More GHG in the air means more heat, which in turn melts more glaciers, causing even more heat from the Sun to become trapped.

The vicious circles that form apparently raise Earth's temperatures by more than scientists predicted when they first developed their climate models, shows a new study by experts at the University of Michigan, in the United States.

Details of the investigation, which covered three decades of satellite data on ice and snow extents in the Northern Hemisphere, is published online in the latest issue of the esteemed journal Nature Geoscience.

UM Department of Atmospheric, Oceanic and Space Sciences assistant professor Mark Flanner led the investigation. He decided to focus his attention on the Northern Hemisphere because this half of the world contains most of Earth's snow and ices.

The Arctic and Greenland will play a crucial role in the future. Most measures that environmentalists are calling for when it comes to mitigating the effects of global warming would be aimed at this areas.

They contain vast amounts of ices which could raise global sea levels considerably, if they melt. Following the study, Flanner determined that average temperature rose by about 0.7 degrees Celsius in the Northern Hemisphere since 1979 (when satellite records began).

“If the Earth were just a static rock, we could calculate precisely what the level of warming would be, given a perturbation to the system. But because of these feedback mechanisms we don't know exactly how the climate will respond to increases in atmospheric carbon dioxide,” the expert says.

“Our analysis of snow and sea ice changes over the last 30 years indicates that this cryospheric feedback is almost twice as strong as what models have simulated,” he goes on to say.

“The implication is that Earth's climate may be more sensitive to increases in atmospheric carbon dioxide and other perturbations than models predict,” Flanner adds, quoted by Eurekalert.

“People sometimes criticize models for being too sensitive to climate perturbations. With respect to cryospheric changes, however, observations suggest the models are a bit sluggish,” he concludes.