Monday, March 12, 2012

New paper finds decreased Arctic sea ice causes increased cloudiness

A paper published today in the journal Geophysical Research Letters finds that decrease in sea ice leads to an increase in cloudiness in the Arctic. Clouds increase the reflection of sunlight (albedo) thereby cooling the Earth and acting as a strong  negative feedback to global warming. Although diminshed sea ice decreases albedo, the resulting increase in cloudiness may act as a natural homeostatic mechanism to stabilize Arctic temperatures.


GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L05705, 5 PP., 2012
doi:10.1029/2012GL051251
Key Points
  • EFA method is valuable in providing quatitative assessment of feedback
  • Decrease in sea ice leads to increase in cloud
  • Further decline in sea ice will likely result in cloudier Arctic
Yinghui Liu
Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin-Madison, Madison, Wisconsin, USA
Jeffrey R. Key
Center for Satellite Applications and Research, NESDIS, NOAA, Madison, Wisconsin, USA
Zhengyu Liu
Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA
Center for Climate Research, University of Wisconsin-Madison, Madison, Wisconsin, USA
Xuanji Wang
Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin-Madison, Madison, Wisconsin, USA
Stephen J. Vavrus
Center for Climate Research, University of Wisconsin-Madison, Madison, Wisconsin, USA
Arctic sea ice cover has decreased dramatically over the last three decades. Global climate models under-predicted this decline, most likely a result of the misrepresentation of one or more processes that influence sea ice. The cloud feedback is the primary source of uncertainty in model simulations, especially in the polar regions. A better understanding of the interaction between sea ice and clouds, and specifically the impact of decreased sea ice on cloud cover, will provide valuable insight into the Arctic climate system and may ultimately help in improving climate model parameterizations. In this study, an equilibrium feedback assessment is employed to quantify the relationship between changes in sea ice and clouds, using satellite-derived sea ice concentration and cloud cover over the period 2000–2010. Results show that a 1% decrease in sea ice concentration leads to a 0.36–0.47% increase in cloud cover, suggesting that a further decline in sea ice cover will result in an even cloudier Arctic.

9 comments:

  1. (1) Clouds = negative feedback.

    (2) ice melts = more clouds = lower temperature = more ice forms.

    (3) But we do know that air temperature is not the major cause of a melting ice pack. Change from -40C to -30C does nothing. Wind and warmer ocean current.

    (4) Epic fail.

    Where do i go to pick up my PhD ? University of Easy Access or University of Wisconsin-Madison ?

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  2. I would guess that more clouds in winter lead to higher temps. But that's just me.

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  3. MS.

    But...

    Clouds only cause cooling in the Summer, they're a net warmer in the Arctic during the Winter/Spring/Autumn #1. And cloud forcing may mean that the Arctic can rapidly shift to a year round ice free Arctic by keeping things warm over the winter #2 #3.

    So you are wrong, it doesn't represent a net negative feedback, it's a net positive feedback. Consider also my following reply to anonymous.

    Anonymous,

    See the above reply - in the Arctic clouds are a net positive feedback.

    The growth of sea-ice is driven by the heat flux through the ice. That heat flux is driven by the temperature difference between the ocean and surface, as ice is an insulator the heat flux reduces as the ice thickens. So even the difference between -30 and -40degC can reduce thickness of sea-ice.

    No PhD, no cigar, epic fail.



    #1 Screen & Simmonds, 2010, "The central role of diminishing sea ice in recent Arctic temperature amplification" figure 3.

    #2 Abbot & Tzipperman, 2008, "Sea ice, high-latitude convection, and equable climates."

    #3 Abbot et al, 2011, "Bifurcations leading to summer Arctic sea ice loss."

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  4. Chris Reynolds:

    Provide your proof that clouds are "a net warmer in the Arctic during the Winter/Spring/Autumn" Computer models don't count as empirical evidence. And don't tell me it's because of increased radiative forcing from clouds - that assumption has already been disproven in the 2 recent water vapor threads and many other threads on this blog.

    Provide empirical proof "cloud forcing may mean that the Arctic can rapidly shift to a year round ice free Arctic by keeping things warm over the winter" Computer models don't count as empirical evidence.

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  5. Chris Reynolds:

    If "Arctic clouds are a net positive feedback" the Arctic would have permanently melted down billions of years ago

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  6. MS,

    The data is from ERA Interim, a reanalysis system that uses observational data filled in using a physics model. It's a development from systems like NCEP/NCAR, a robust technique used by weather services the world over. I use NCEP/NCAR because I'm aware of issues with it and it's free - ERA Interim costs money to use.

    Your suggestion that if clouds were a net +ve feedback the Arctic would be ice free is flawed. Clouds do what they do - they are a part of the system. The observations I outline are with regards recent change. And as I point out with regards Abbot, clouds may have a future role in keeping the Arctic sea-ice free once the transition to a seasonally sea ice free state is reached within the next few decades. Indeed the Abbot/Tzipperman hypothesis was put forward to explain periods in the past when the Arctic was sea-ice free but CO2 levels don't seem to have been high enough to maintain that state. In essence increased inwards atmospheric heat flux combined with the warming effect of a blanket of cloud kept the Arctic temperate through the winter (allowing forests along the arctic coast).

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  7. Chris Reynolds:

    As previously stated, computer models such as ERA-Interim prove nothing, and most assuredly do not prove Arctic clouds or any clouds for that matter result in net positive feedback. Even the alarmist IPCC admits in AR4 they don't know if clouds result in negative or positive feedback and furthermore that they don't know if water vapor results in a net negative or positive feedback.

    All net positive feedback systems are inherently unstable. If your theory was correct, an ice-free Arctic would have caused the primary greenhouse gas water vapor (regardless of CO2 levels) to result in ever increasing temperature leading to ever increasing water vapor ad infinitum.

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  8. MS,

    "computer models such as ERA-Interim prove nothing"

    But you are using the results of a model in your opening post.

    I use NCEP/NCAR and have found it's fidelity to what I see in NOAA weather observation sites excellent. Especially when going back to review what caused a particular cold snap etc. ERA-Interim is reported to be a signifcant improvement on ERA-Interim.

    All positive feedback systems are not inherently unstable. We have a 300MHz to 21GHz frequency generator in our lab, its stable in frequency enough to measure down to the 1ppm level, its second harmonic is over 80dB down, and it is left on 24/365 to ensure it's stability. It does not run away with itself. Oscillation depends on positive feedback.

    Positive feedback and negative feedback is a key part of the climate system, yet the climate system doesn't run away unless perturbed, e.g. Solar forcing during Maunder Minimum or GHG forcing causing most of the post 1975 warming, with other human factors accounting for the rest.

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  9. "But you are using the results of a model in your opening post"

    Nope- the paper is based on "satellite-derived sea ice concentration and cloud cover over the period 2000–2010"

    "All positive feedback systems are not inherently unstable"

    You again misquote me. I said "All NET positive feedback systems are inherently unstable" which is absolutely true. The system you describe has an equivalent negative feedback at equilibrium in order to be stable.

    "other human factors accounting for the rest"

    Again you make pronouncements with no supporting evidence. BTW, computer models do NOT provide data NOR evidence.

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