Clouds could explain how Snowball Earth thawed out

Nov 13, 2012
Credit: NASA

Glaciation events during the Neoproterozoic (524-to-1,000 million years ago) and Paleoproterozoic (1,600-to-2,500 million years ago) periods - events that spawned ice ages that persisted for millions of years at a time - may have seen glacier ice encircle the planet in a frosty planetary configuration known as a Snowball Earth.

Whether the planet could have existed in such a state, however, is a matter of considerable debate. An elevated planetary albedo, caused by the planet being covered in reflective snow and ice, would mean that a would reinforce itself. With no known mechanisms able to fully explain how the planet could have thawed out from such a state, some scientists suspect that Snowball Earth never happened.

However, using a series of global general circulation models, Abbot et al. find that the greenhouse potential of clouds, which had been overlooked in previous research, could explain how a Snowball Earth may have melted.

Previous modeling research found that to thaw out a glacier that covered the planet would require carbon dioxide to account for up to 20 percent of the atmosphere by volume. Paleogeochemical evidence, however, shows that carbon dioxide levels reached only 1 percent to 10 percent. The model used for the earlier research, the authors find, ignored the warming potential of clouds.

Clouds not only trap infrared radiation near Earth's surface, warming the planet, but also reflect , cooling the planet. In the modern climate, both effects are important. However, set against a planet encompassed in ice, clouds' reflectivity becomes less important, and the overall effect of clouds is to warm the planet.

By accounting for the heat-trapping effects of clouds, the authors find that the concentration required to drive deglaciation is 10-100 times lower than previous research suggested, a concentration that fits within observed levels.

Explore further: Climate change does not cause extreme winters, new study shows

More information: Clouds and Snowball Earth Deglaciation, Geophysical Research Letters, doi: 10.1029/2012GL052861 , 2012

add to favorites email to friend print save as pdf

Related Stories

Scientists study 'Snowball Earth'

Nov 28, 2006

Canadian scientists have determined the factors involved in ending a severe ice age 750 million years ago that nearly completely froze Earth's oceans.

Snowball Earth hypothesis challenged

Oct 12, 2011

The hypothesis that the Earth was completely covered in ice 635 million years ago has received a serious blow. The atmospheric concentration of CO2 during that period was much lower than previously thought, ...

Thawing a planet-sized snowball

Nov 05, 2010

These days the climate news is all about global warming, but global freezing was the biggest climate worry in Earth's distant past.

Early Earth may have been prone to deep freezes: study

Dec 05, 2011

Two University of Colorado Boulder researchers who have adapted a three-dimensional, general circulation model of Earth's climate to a time some 2.8 billion years ago when the sun was significantly fainter than present think ...

A curious cold layer in the atmosphere of Venus

Oct 01, 2012

(—Venus Express has spied a surprisingly cold region high in the planet's atmosphere that may be frigid enough for carbon dioxide to freeze out as ice or snow.

Update on Gliese 581d's habitability

May 09, 2011

When last we checked in on Gliese 581d, a team from the University of Paris had suggested that the popular exoplanet, Gliese 581d may be habitable. This super-Earth found itself just on the edge of the Gold ...

Recommended for you

Image: Aral Sea from orbit

13 hours ago

This multitemporal Sentinel-1A radar image shows the Aral Sea, located on the border between Kazakhstan and Uzbekistan in Central Asia.

IceBridge overflies Norwegian camp on drifting sea ice

15 hours ago

Studying sea ice in the Fram Strait, a passage between Greenland and Svalbard that is the main gateway for Arctic sea ice into the open ocean, is not easy. In this area, not only does ice flow southward quickly ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (5) Nov 13, 2012
One point has been overlooked. If pan-globe ice cover is achieved, the surface-reflection of daylight back up into the atmosphere would be like having a sun shining on most air from above AND below! So during daylight the moist air is too warm to condense into clouds even when 'supersaturated'. As moist air regions rotates towards the nightside of the planet, the moist air condenses into clouds which reflect back DOWN any latent heat IR radiated from surface/lower atmosphere. When again in daylight, these clouds would 'evaporate' to transparent moisture once more and not reflect away any daylight from above. Hence the cloud effect would then have bee more 'biased' than today's 'balanced' dynamics of condensing anytime conditions are right, day OR night. Just an observation given 'snowball earth' was ever to such a global coverage as alleged. Cheers!
not rated yet Nov 14, 2012
"Clouds would 'evaporate' to transparent moisture"

Transparent at what wavelengths?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.