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A Flanner in the Works for Snow and Ice

Posted on 23 January 2011 by MarkR

A new paper by Flanner et al in Nature Geosciences tries to estimate the so called ‘cryosphere albedo feedback’ since 1979. As Earth warms, ice and snow melt and the loss of their shiny, reflective surfaces means more sunlight is absorbed and global warming receives a boost.

The strength of a feedback can be calculated from how much extra heating it adds as temperatures increase; the equations are here. Climate models expect that changes in Northern Hemisphere snow and ice since 1979 should have been a positive feedback of about 0.25 W m-2 K-1 - i.e. for each degree of global warming, the loss of snow and ice means that another 0.25 W of sunlight is absorbed per square metre of the Northern Hemisphere. Globally, and in the long run it’s expected to be 0.2 because there’s less snow in the south and you eventually run out of summer snow to melt.

Flanner et al use satellites to measure the change in shortwave (i.e. sunlight) reflectivity across the Northern Hemisphere from 1979 to 2008. 

They find the total amount of cooling that ice & snow provide to the Northern Hemisphere month by month split between sea ice and snow:

Figure 1a) is the total cooling effect by month of snow, ice and snow+ice. b) is the change in cooling effect for each month since 1979 split into snow, ice and snow+ice. Positive means melting has led to more warming, negative means it’s added to cooling.

Even though there is much more ice in the winter, the days are shorter and the sunlight weaker so the total cooling effect is smaller. May to June ice & snow is much more important even though there is less of it. Next they made annual averages and mapped these over the hemisphere:

Figure 2a) total cooling effect and b) change in cooling effect since 1979 in snow and ice of the Northern Hemisphere.

The authors find that the total effect is 0.33-1.07 W m-2 K-1 with a best estimate of 0.62 W m-2 K-1, significantly higher than climate models’ 0.25 W m-2 K-1. Models have underestimated the darkening of the Northern Hemisphere and therefore how much global warming we’re ultimately in for.

Perhaps the first snow and ice melted more quickly than expected and eventually we’ll run out of the easy to melt bits, or maybe the decline in Arctic sea ice will halt for ~30 years to bring it back in line with models. However, if the current pattern holds then this would boost the best estimate of global warming temperature rises by about 20% - here’s hoping it’s just a blip!

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Comments 151 to 156 out of 156:

  1. Because, Ken, Trenberth's figure is a figure for how energy is used, not for where it comes from. Therefore it is irrelevant to the discussion. You cannot just pick out one heat sink and say that that determines the total energy flows into and out of a system and neglect the other five (at minimum) heat sinks in the system. Of course, when I say, "You cannot..." I assume I address a reasonable person.
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  2. Yet another report on the deteriorating Arctic: ... so-called feedback effects, are of major significance for how extensive global warming will be in the future. ... One of the most important right now is the reduction of the Arctic’s albedo. The decrease in the snow- and ice-covered surfaces means that less solar radiation is reflected back out into the atmosphere. It is absorbed instead, with temperatures rising as a result. Thus the Arctic has entered a stage where it is itself reinforcing climate change. ... The report “Impacts of climate change on snow, water, ice and permafrost in the Arctic” has been compiled by close to 200 polar researchers. It is the most comprehensive synthesis of knowledge about the Arctic that has been presented in the last six years. 200 researchers agree? Surely there's a lone voice of sanity somewhere out there to buck what could only be called a 'consensus.'
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  3. Tom Curtis #148 "However, in light of Lambert's unsavoury characteristic of claiming victory anytime a response delayed, in light of his incapability of admitting error coupled with a determination to score rhetorical points of the errors of others, and in light of his inability to keep even simple concepts straight (as for example the difference between change in incoming energy due to change in albedo (as discussed here) as distinct from the amount of energy used to melt a particular volume of ice (which he repeatedly treats as equivalent), no response will be forthcoming. I find arguments from obtuseness uninteresting - and evidently, that is all that Lambert has to offer this forum." In a spirit of goodwill Tom, I will restrain myself from suggesting that you have thrown in the towel. Would you prefer that I ignore the 'the errors of others' while being pilloried with terms such as 'ridiculous' and 'fool' when producing sound calculations based on the information from Dr Trenberth - a leading scientist in this field? I would be failing in a duty to myself and the readers of this site if I allowed gross errors to go unremarked which are intended to disprove and damage my arguments. Several time you have discovered errors and re-calculated -- only after I pointed them out. You even produced bizarre gems like this: "More usefully, the average annual temperature anomaly between the 80's and the 2000's for the area from 67 degrees north to the pole is 1.2832875654 degrees C." Was that a joke I missed or were you trying to impress the gullible by quoting a temperature to 10 decimal places? You have admitted that none of my calculations were wrong. You have disputed my assumptions, and I have disputed yours. Mine produced results close to the NET heat absorption calculated by Dr Trenberth - yours don't. Let that be the end of this fraught but necessary encounter.
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  4. Ken Lambert @153: 1) Why be charitable? You have already taken the opportunity of my mother's ill health and my being preoccupied with helping family members shift house to declare victory. Why should this time be any different? 2) It is not your attention to the "errors of others" which makes your character questionable - it is your inability to acknowledge any error you yourself make. 3) Apposite of which, your "assumptions" have been irrelevant to every error of yours I have pointed to. That is because I calculated a particular value, ie, the net incoming energy absorbed by the arctic the summer season of 2010 - the net incoming energy absorbed by the arctic in the summer season of 1979. I know when I calculate that value and get a figure in Watts per square meter, and then I multiply by the area by 60 by 60 by 24 by 90 that I have calculated a value for a 90 day period. Your assuming that the value is actually that of a thirty day period is therefore just an error. It is, what's more an error that you repeated several times after correction, and have never admitted to. It is not an error of calculation simply because you do not bother doing the sums. In like manner, when I actually look up the monthly data for sea ice area for the respective periods, and determine the difference in sea ice area between 1979 and 2010, your assumption that the actual loss of area over that thirty year period is just the loss of sea ice calculated by Trenberth for a single year is again simply an error. It is just as much an error as if you used the diameter of the moon to calculate the surface area of the Earth, and no matter how exact your equations are, the error in the initial values means your equations are useless. 4) With regard to the decimal places, sometimes it is just easier to cut and paste. The number of decimals means nothing more, nor less than that. Typically, you however try to make so simple a matter the basis of an ad hominen. 5) Finally, your argument style of making a false statement, ignoring the correction, making it again, and ignoring the correction, and making it again, and so on until you hold the field by exhaustion of the opposition shows an absolute lack of intellectual integrity. It reminds me of nothing so much as the debating style of some creationists I have known.
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  5. 153, Ken, 154, Tom, We all need to avoid the tactic of declaring victory rather than achieving it, and that of simply broadcasting a perception of the errors of others, rather than actually proving them. That said... it is utterly reprehensible to simply lie about what others have said, or to pretend that the previous thread of the conversation says something entirely different from the truth of the matter. It will also be reprehensible to jump on this comment and righteously accuse the other party of such guilt. Anyone who looks at this stream of comments is well advised to go back and judge that aspect of this particular debate for themselves. The evidence is mostly there (except for the utterly outrageous posts which were deleted by the moderators), and the behavior in question will be easy enough to identify. Just look for the comments that keep declaring victory, or claiming to have previously found and proven mistakes by others (without actually doing so, or by quietly ignoring any substantive rebuttals).
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  6. muoncounter I assume that your attempt to inject a little humour means that you can't really disagree with my parting comment at #149 MC? Tom seems to have vacated the field for other threads.
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