A new study published online in the journal Nature Geoscience has uncovered data that shows over the past 30 years the decreases in the amount of snow and ice covering the Earth’s surface has decreased the reflective capacity of the Earth and exacerbated global warming much more than previous climate models had estimated.
“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.”
The findings refer to the albedo feedback; the ability of the cryosphere – that collective portion of the planet which contains water in its solid form, including sea ice, snow, lake and river ice, glaciers, ice sheets and frozen ground – to reflect the suns warming rays away from the surface.
This albedo feedback sees frozen surfaces diminish, leaving in their wake surfaces such as water and solid earth which both retain heat better than they reflect it, which in turns increases the warming and thus the melting which decreases the reflectivity of the area in a massive loop which never turns off.
“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,” said Mark Flanner, an assistant professor in the Department of Atmospheric, Oceanic and Space Sciences at the University of Michigan. “But because of these feedback mechanisms we don’t know exactly how the climate will respond to increases in atmospheric carbon dioxide.”
“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. The implication is that Earth’s climate may be more sensitive to increases in atmospheric carbon dioxide and other perturbations than models predict.”
“Some of the decline may be natural climate variability,” Shell said. “Thirty years isn’t a long enough time period to attribute this entirely to ‘forcing,’ or anthropogenic influence. But the loss of cooling is significant. The rate of energy being absorbed by the Earth through cryosphere decline – instead of being reflected back to the atmosphere – is almost 30 percent of the rate of extra energy absorption due to carbon dioxide increase between pre-industrial values and today.”
As Shell said, this is not necessarily the result of anthropogenic warming, but it is happening and has yet to be calculated into climate models; as a result the possible damage caused is unknown.