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14% Less Solar Energy Reflected Back to Space

Posted by feww on January 17, 2011

Dwindling Snow and Ice Cover Reflect 0.45Wm-² Less sunshine to Space: Study

Ever-shrinking snow and ice cover in the Northern Hemisphere, which contribute to “cyrospheric cooling,” now reflect only about 3.3Wm-² Solar Energy back to space, an average of 0.45Wm-² less than they did in the late 1970s, a new study says.

Cyrospheric cooling has declined by an average of 0.45 W m-² from 1979 to 2008, according to the study, which was published in the Nature Geoscience journal Sunday.

The following is an excerpt from the report abstract:

The extent of snow cover and sea ice in the Northern Hemisphere has declined since 1979, coincident with hemispheric warming and indicative of a positive feedback of surface reflectivity on climate. This albedo feedback of snow on land has been quantified from observations at seasonal timescales and century-scale feedback has been assessed using climate models. However, the total impact of the cryosphere on radiative forcing and albedo feedback has yet to be determined from measurements. Here we assess the influence of the Northern Hemisphere cryosphere on Earth’s radiation budget at the top of the atmosphere—termed cryosphere radiative forcing—by synthesizing a variety of remote sensing and field measurements. We estimate mean Northern Hemisphere forcing at −4.6 to −2.2 Wm-², with a peak in May of −9.0±2.7 Wm-².

The planet’s shrinking snow and sea ice cover means less heat reflected back to space resulting in a positive feedback loop heating the globe. The warming is intensifying at a higher rate than climate  models have predicted, according to new research. Image Credit: Mark Flanner.

[Moderator’s Note: The cryosphere refers to those parts of our planet where water is in solid form including glaciers, ice caps, ice sheets, sea ice, snow cover and the permafrost.]

Scale of Positive Feedback

For each degree Kelvin (1.8 degree Fahrenheit) increase in temperatures, which reduces the Northern Hemisphere’s snow and ice cover, the solar energy reflected back to space decreases by between 0.3 and 1.1Wm-²K-². The study conclude that the albedo feedback from the Northern Hemisphere cryosphere decline is “substantially larger” when compared to estimates obtained from 18 other climate models. That is an average shortfall of 0.6Wm-² in Flanner’s research compared to IPCC allowance of 0.25Wm-² over the same period.

The reduction in cyrospheric cooling effect, caused by snow and ice cover losses, increases the amount of solar energy that our planet absorbs, Mark Flanner, an assistant professor at the University of Michigan and lead author of the study, told Reuters.

1979–2008 time series of cryosphere radiative forcing (CrRF) anomalies, relative to 1979–2008 means, from land-based snow, sea-ice, and the combination of both components. Each line depicts the mean anomalies of the 12 all-sky scenarios of albedo contrast and ∂F/∂α listed in Tables 1 and 2, and shading indicates the full range of anomalies for the snow+sea-ice forcing from all 12 cases. The 5-year moving average of snow+sea-ice forcing anomaly is shown in orange. Credit:  Mark Flanner et al. ‘Radiative forcing and albedo feedback from the Northern Hemisphere cryosphere between 1979 and 2008’

How does the new estimate compare with previous climate models?

“This reduction in reflected solar energy through warming is greater than simulated by the current crop of climate models,” Flanner said.

“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.”

“The cryospheric albedo feedback is a relatively small player globally, but it’s been a surprisingly strong feedback mechanism over the past 30 years,” Flanner said. “A feedback of this magnitude would translate into roughly 15 percent more warming, given current understanding of other feedback mechanisms.”

“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,” he said.

“The conclusion is that the cryosphere is both responding more sensitively to, and also driving, stronger climate change than thought.”

The Cyrospheric Impact on Our Planet

“On a global scale, the planet absorbs solar energy at a rate of about 240 watts per square meter averaged over a year. The planet would be darker and absorb an additional 3.3 watts without the Northern Hemisphere cryosphere,” Flanner said.

“The cryospheric albedo feedback is a relatively small player globally, but it’s been a surprisingly strong feedback mechanism over the past 30 years,” Flanner said. “A feedback of this magnitude would translate into roughly 15 percent more warming, given current understanding of other feedback mechanisms.”

Top 10 Warmest Years

The 1901-2000 average combined land and ocean annual temperature is 13.9°C (56.9°F), the annually averaged land temperature for the same period is 8.5°C (47.3°F), and the long-term annually averaged sea surface temperature is 16.1°C (60.9°F). Source: NOAA.

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2 Responses to “14% Less Solar Energy Reflected Back to Space”

  1. Jack said

    [Any credible source for the opening salvo? Moderator]

    Why throw so much faith behind numbers that are not adding up? Austraila is blanketed in clouds, they will not absorb enough heat, being an ice cube this winter.

    [The numbers add up pretty well, AND Australia is not blanketed by clouds. You can check daily satellite images at — also check for daily temperatures. Perth was 34°C and mostly sunny today. You seem to have overlooked a tiny technicality that it’s summertime downunder. Moderator]

    • Jack said

      [Jack, your comments are increasingly unintelligent and off the mark. Some of the stuff could only come from the anatomical region you referred to rhetorically. Moderator]

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