ExClimate: The Ice Albedo Feedback mechanism and Snowball earth

This article is a little bit of a tangent to my regular articles. I am presently doing an online course - Climate Change: Challenges and solutions - offered by the University of Exeter (UK). So please indulge me as I also use this blog for some climate course work. This article is for section 2.3 of the course on Snowball earth events that have ocurred in the distant past.

No one is sure what precipitated the onset of snowball earth events. The oldest snowball earth event occurred approximately 2200 million years ago. The most recent event ended about 635 million years ago and is thought to have lasted 6 to 12 million years. Very basic life managed to survive at least the most recent snowball earth event.

The earth's orbit around the sun, it's axial tilt, and wobble all have different millenial cycles which can affect the amount of solar radiation being absorbed by the earth. Earth’s orbit changes from near circular to oval shape on a 100,000-year cycle (eccentricity). Earth’s axis is tilted and is presently at 23.5 degrees. It varies between 21.5 and 24.5 degrees every 41,000 years (obliquity - Milankovitch cycles). As the Earth spins it wobbles on its axis toward and away from the Sun over the span of 19,000 to 23,000 years (precession).

What caused the earth to go into a giant snowball is still being debated in scientific circles. A number of theories have been advanced including :

• a reduction in solar output,
  
• the Earth passing through rare space clouds,
  
• a combination of high obliquity in the Earth's orbit, orbital eccentricity or precession;
  
• Lithospheric weathering reducing atmospheric carbon causing planetary cooling
  

Climate Feedback: Arctic sea ice changes increase light absorption and ocean warming

A new study has examined the impact of changing sea ice and light absorption in the Arctic to reveal another climate feedback mechanism.

As multi-year sea ice is replaced with thinner first year sea ice, the properties of the sea ice change to allow more light through to the water beneath increasing ocean warming and more melting of sea ice.

Arctic Summer Sea Ice Extent Minimum record smashed in 2012

Arctic summer sea ice is at a new record low level since satellite measurements began recording data in 1979. The summer minimum is down to about 1.32 million square miles (3.41 million square kilometers), half the average summer ice between 1979 and 2000. The minimum record was last set in 2007 with this year's sea-ice extent being about 18% lower than 2007. Some scientists predict we may see summer sea ice vanish by 2015-16, well ahead of International Panel on Climate Change (IPCC) 2007 Report predictions.

"The polar meltdown shows we're teetering on the brink of climate-change catastrophe," said Shaye Wolf, climate science director at the Center for Biological Diversity's Climate Law Institute. "Arctic sea ice plays a critical role in regulating the planet's climate. As man-made global warming shrinks the ice, our risk of droughts and other extreme weather goes up. We can't wait any longer to cut carbon pollution."

See also: Arctic sea ice Extent drops to lowest on record and still shrinking | Arctic warming at more than double the global warming average | Sea ice volume: Multi-year arctic sea ice reducing dramatically | Radio Ecoshock: ARCTIC MELT DOWN Scientists Speak Out | Climate Code Red: How British government's climate forecasting MET Office gets the Arctic wrong

Arctic warming at more than double the global warming average

A new scientific study warns that the Arctic is warming at up to four times faster than the global average, due to the combination of melting sea ice and global atmospheric warming.

See also: July 2011 - Warming Arctic air temperatures causing less snow, more rain, faster ice melt | Jan 2011 - Albedo Feedback: Climate Models under estimate loss of reflectivity in the Arctic

Greenland melting in 2011 well above average with near-record mass loss

Professor Marco Tedesco from the City College of New York reports that extreme melting continues from the Greenland Ice sheet this year with close-to-record simulated surface mass balance, bare ice exposure, albedo and runoff anomalies. He warned that glaciers could undergo a self-amplifying cycle of melting and warming that would be difficult to halt.

Related: Record summer melting in 2010 | Greenland sets a new melt record in 2010 - sea levels to rise

Warming Arctic air temperatures causing less snow, more rain, faster ice melt

Arctic air temperatures are warming faster than anywhere else on Earth. Although the level of precipitation is remaining unchanged, there is reduced snowfall in summer which is being replaced by increasing rain. The loss of summer snow and increase in rain is resulting in a positive feedback mechanism increasing warming and melting of the Arctic ice.

We are already witnessing an increase in the Albedo feedback mechanism - loss of reflectivity in the arctic leading to more warming and greater ice melt. Research published early in 2011 revealed Loss of reflectivity in the Arctic is double the estimate used in climate models. With the change in precipitation we have a further feedback mechanism contributing to Arctic warming and melting of snow and sea ice.

Albedo Feedback: Climate Models under estimate loss of reflectivity in the Arctic

Loss of reflectivity in the Arctic is double the estimate used in current state-of-art climate models according to new analysis of the Northern Hemisphere's "albedo feedback" over a 30-year period.

The albedo feedback is the change in the reflectivity of surfaces in a constant reinforcing feedback loop. In the Arctic snow and ice is highly reflective. Global warming has reduced sea ice exposing darker ocean and increased the size of dark melt pools on the Greenland ice sheet, which then increases the warming effect on ice in a positive feedback.

"The cryosphere isn't cooling the Earth as much as it did 30 years ago, and climate model simulations do not reproduce this recent effect," said Karen Shell, an Oregon State University atmospheric scientist and one of the authors of the study. "Though we don't necessarily attribute this to global warming, it is interesting to note that none of the climate models used for the 2007 International Panel on Climate Change report showed a decrease of this magnitude."