Feedbacks, Feedbacks, awful, awful

There is this well known ice albedo feedback. Albedo is another name for the percentage of sunlight, which is reflected back into space. The albedo of ice is considerably bigger than that of the sea surface. When (not if) the summer sea ice vanishes, which is in full swing, the polar sea absorbs more sunlight. Result: climate change will be sped up generally and disproportionally in the arctic .

Lately, another important feedback mechanism has come to public attention: the spring and summer snow cover on land. In the course of the polar warming, it has shrunk, naturally, as can be seen in this graph (source):

june snow cover

It is interesting to compare the areas affected:

1980 ca.

2012 ca.

Minimum Sea Ice Area (Mio km²) ca.



June Snow Cover Area (Mio. km²) ca.



As You can see, the area drop of summer snow is a little bit less than the double of summer sea ice.

As often, things are more complex than they appear at first sight:

  • The snow data are “extent” – data which means, that they contain 10 – 15 % snow free area.
  • The albedo of land is bigger than that of water (ca. 0.2 vs. ca. 0.1, source).
  • Contrary to intuition, the mean solar irradiation in mid summer in those areas, where the main snow melting difference occurs (around the 60° N) is lower than on the polar sea around the north pole!
  • The data for other months than June are not given in my source, probably in the paywalled original paper, so they might look less crassy.

On the other hand, the capacity of heat absorbtion of land is smaller than that of sea surface, which will direct the absorbed energy earlier into atmosphere instead of the water body. Also, the speed of recent summer snow loss seems to be higher than that of sea ice (source).

What is the bottom line of all this discussion?

It is safe to say, that the climate feedback effects of sea ice – and land snow cover decline are of comparable size and that the latter should definitely be reckoned with.

Is that something new?

For science –  not, besides that the rate of snow area loss is (AFAIK) as unforeseen as that of ice loss. For the public – yes, this aspect has scarcely been covered by media.

Are there effects other than general climate warming?

Yes, as with sea ice loss, the weather system is beeing changed, i.e. strength, position and movement of lows and highs. But knowledge about that aspect is still not quite settled. (How could it?) And don’t forget the perils of arctic methane release, which is still low compared to tropical release rates, but could be considerably accelerated by permafrost thaw.

Does this have any significance for our daily life?

No, besides the feeling of urgency becomes stronger to tap on the brake pedal with emissions.

What would be a nice thing concerning this?

Put a price on GHGs emission, be it by a comprehensive, working cap and trade system or tax.


6 Responses to “Feedbacks, Feedbacks, awful, awful”

  1. 1 crandles
    January 10, 2013 at 11:29 am

    Twice the area, more southerly, and lower heat capacity all makes it seem much more important than sea ice. But is this fair? The area difference in July, August and September is presumably much smaller for snow cover. There is also the sun angle in June makes June more important than September. Perhaps totals for each summer month for 1980 and 2012 would be interesting. Don’t know if attempting to weight them for importance would be possible or too prone to error.

    • 2 kinimod
      January 11, 2013 at 2:59 am

      Unfortunately I did not find the area differences for other months.
      There are also other aspects reducing the “double” effect to a “more or less equal” effect.
      I gave the post an overhaul. It is no more quite as spectacular but more sound.

  2. 3 bert
    January 10, 2013 at 6:56 pm

    Logical and useful – thanks (except the jump to cap and trade). We need to reduce emissions yes, but why not a carbon tax?

    • 4 kinimod
      January 11, 2013 at 3:49 pm

      I am not married to cap and trade. Anything will do, if it’s done determinedly. It’s just because here in Europe we have a cap and trade, only it’s without teeth because of lobbying.

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