Guest Post by Willis Eschenbach
Anthony has just posted the results from a “Press Session” at the AGU conference. In it the authors make two claims of interest. The first is that there has been a five percent decrease in the summer Arctic albedo since the year 2000:
A decline in the region’s albedo – its reflectivity, in effect – has been a key concern among scientists since the summer Arctic sea ice cover began shrinking in recent decades. As more of the sun’s energy is absorbed by the climate system, it enhances ongoing warming in the region, which is more pronounced than anywhere else on the planet.
Since the year 2000, the rate of absorbed solar radiation in the Arctic in June, July and August has increased by five percent, said Norman Loeb, of NASA’s Langley Research Center, Hampton, Virginia. The measurement is made by NASA’s Clouds and the Earth’s Radiant Energy System (CERES) instruments, which fly on multiple satellites.
The second related claim is as follows:
Kay and colleagues have also analyzed satellite observations of Arctic clouds during this same 15-year period. Kay’s research shows summer cloud amounts and vertical structure are not being affected by summer sea ice loss. While surprising, the observations show that the bright sea ice surface is not automatically replaced by bright clouds. Indeed, sea ice loss, not clouds, explain the increases in absorbed solar radiation measured by CERES.
Since I have the latest CERES data on my computer, I figured I’d see what they were talking about.
Now, it’s not entirely clear from the presentation which dataset they’ve used. Bear in mind that there are two CERES datasets: top-of-atmosphere radiation observations, and surface radiation calculations. Albedo is calculated from the observations, it’s reflected sunlight divided by incoming solar.
On the other hand, they also talk about “absorbed solar radiation” which is only available in the calculated datasets.
So let’s start with the claim that the Arctic albedo has decreased since the year 2000. I assume that they are using the normal definition of “Arctic”, which is above the Arctic Circle at about 66.5° north.
There are several difficulties with albedo near the poles. First, when the total solar input is quite small, the numbers get inaccurate, since it is a ratio and the denominator, the solar input, is near zero. In addition, the numbers are also inaccurate because there’s so little reflected sunlight, which makes both the top and bottom of the ratio quite variable. Finally, it’s difficult to convert the changes in albedo into watts per square metre (W/m2), which is a much more meaningful number.
So let me look at a simpler measurement—how much sunlight is reflected, measured in W/m2. We have three top-of-atmosphere (TOA) observational datasets for that, which are the reflection regardless of the state of cloudiness (called “toa_sw_all”), the reflection from the ground when the sky is clear (called “toa_sw_clr”), and the reflection just from the clouds (called “cre_sw”). Figure 1 shows the first of these, the total sunlight reflected in all conditions:
Figure 1. Total reflection from the Arctic. This includes both cloud and ground reflections. The top panel shows the raw data, with a dotted line showing the average value. The middle panel shows the seasonal component, which is also called the “climatology”. The bottom panel shows the “residual”, which is the difference between the top and middle panels.
I note that indeed the reflections have gotten smaller over the period, meaning that the amount absorbed is larger as the press release stated. The next graph, Figure 2, shows the ground reflections only. Note that as you’d expect, these are less than the total reflections:
Figure 2. “Clear sky” (ground only) reflections from the Arctic. This shows only ground reflections. The top panel shows the raw data, with a dotted line showing the average value. The middle panel shows the seasonal component, which is also called the “climatology”. The bottom panel shows the “residual”, which is the difference between the top and middle panels.
Finally, Figure 3 shows the results from just cloud reflections. Note that rather than decreasing, the cloud reflections are increasing. They are also smaller than the ground reflections.
Figure 3. Cloud reflections from the Arctic. This shows only the effect of the clouds. The top panel shows the raw data, with a dotted line showing the average value. The middle panel shows the seasonal component, which is also called the “climatology”. The bottom panel shows the “residual”, which is the difference between the top and middle panels.
So … there are the three graphs: total reflections, ground reflections, and cloud reflections. So how well does this agree with the claims of the press release?
Now, to start with they’ve done something strange. Rather than look at the changes over the whole year, they’ve only looked at three months of the year, June, July, and August. I disagree strongly with this kind of analysis, for a couple of reasons. The first is because it allows for nearly invisible cherry picking, by simply choosing the months with a particular desired effect. The second is that it makes it hard to determine statistical significance, since there are 12 possible 3-month contiguous chunks that they could choose from … which means that you need to find a much greater effect to claim significance.
So I’m not going to follow that plan. I’m looking at what happens over the whole year, since that’s what really matters. The first point of interest is that the total amount reflected from the Arctic (Figure 1) has indeed decreased over the period at a rate of a quarter of a watt per square metre (-0.25 W/m2) per decade … for a total drop in reflected solar of
-0.025 W/m2/year * 14 years = 0.35 W/m2
A third of a watt per square metre? All of this hype in the press release is to announce that there’s been a change in Arctic reflections of a third of a watt per square metre in fourteen years??? Be still, my beating heart … that’s a whacking great 1% change in the already small Arctic solar absorption in fourteen years. This is their big news? Now please note, their claim about the change in June, July, and August of a 5% change may indeed be true … but that just emphasizes why that kind of analysis is just cherry picking.
Not much else to say about it once I’ve said that … well, except to say that their claim that “the bright sea ice surface is not automatically replaced by bright clouds” also doesn’t seem to be true. Note that the blue line in the bottom panel of Figure 3, which shows the smoothed changes of cloud reflections, is pretty much a mirror image of the corresponding line in Figure 2 showing the smoothed changes in ground reflections. In fact, the correlation between the unsmoothed cloud and ground residuals is -0.71, with a p-value less than .001. In other words … they’re wrong. The cloud changes do not entirely offset the ground changes, but the bright clouds assuredly move in total opposition to the bright sea ice surface.
Finally, I would note that from 2000 to 2010, the total reflection from the Arctic drops by about one W/m2 (blue line, bottom panel, Figure 1). Then in two years it drops another one W/m2 … and in the next two years it rises by one W/m2. As a result, I’d have to conclude that while these changes may have statistical significance, they may not mean a whole lot …
Regards to all,
w.
PS—If you disagree with someone, please have the courtesy to QUOTE THEIR EXACT WORDS so that we can all understand the nature of your objections.
CODE AND DATA: The R code and functions are here in a 14 Kb zipped folder . The CERES TOA data is here and the surface data is here. WARNING: BIG data files, 200 Mb plus.
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I’ve always been fascinated by the idea of ‘the top of the atmosphere’, given the wildly different conditions that prevail in different parts of the world.
For instance is the TOA over the Sahara the same as over the Poles?
Is the top of the atmosphere over the Himalayas or Rockies the same as over the Great Plains?
Is the top of the atmosphere over Equatorial Ocean or Forest the same as the top of the atmosphere over the Great Lakes?
Given that Water Vapour, the cardinal greenhouse gas acts differently in all of these locations (in terms of its vertical extent.) Just exactly where do they measure it?
Here is something from an earlier time. It seems that 15 years is too short and that the jury is still out. Nobody knows where Arctic sea ice will be in 2030.
“Now, to start with they’ve done something strange. Rather than look at the changes over the whole year, they’ve only looked at three months of the year, June, July, and August.”
Its dark in the Arctic in winter time. Good luck looking for changes in reflected light in perpetual darkness.
Hmmm. If you are focusing on solar input, then you’d use a period symmetric around the Summer Solstice in late June? e.g. Apparently they’ve selected a period when there is sunlight but less sea ice? Justifiable? Damned if I know
If nothing else, the sea ice extent plots tell us 1 April through 30 September are the relevant months. If the data is available on a daily basis, then the relevant period is equinox to equinox.
Similar to my thoughts except I was willing to accept that it is justified.
They are trying to investigate two signals – sea ice and sunlight. So they picked the time when the “sum” of both signals was strongest.
Yes, that can lead to an increased chance of a false positive but, as a first step, it seems to be perfectly justifiable.
If nothing turns up here then you know nothing has been lost in the noise.
Depends on how far north in the
artic. North of the Arctic Circle, the sun is above the horizon for 24 continuous hours at least once per year (and therefore visible at midnight) and below the horizon for 24 continuous hours at least once per year (and therefore not visible at noon). Only no sunshine for one day at the southern parts of the artic like at the artic circle itself.
The quantification of 0.35 W/m2 for the year, if correct, is still the valid and key point. The net warming force is 1/10th the alleged doubling force of CO2, which has been difficult to show conclusively. The impact of the reduced albedo per se would be impossible to demonstrate. For those who want observations, not just modeling, this work wouldn’t do.
“Perpetual darkness”? In fact there is almost perpetual light in the Arctic in May and more than 12 hours daylight in April and most of September. However, snow melt doesn’t really start until late in May, so there is a lot of sunlight and very high reflection in both April and May, which is undoubtedly why these months aren’t included.
In fact many arctic and subarctic languages have a special word for this season, which has a lot of light but when there is still snow cover. The Swedish word for example translates as “springwinter”.
Agree.
The albedo is difficult to measure during winter since there is little sunlight available at >66N, and the albedo matters only a little during winter. I guess sooty muddy snow cools faster in darkness under a clear sky, but does it matter much?
So there’s no sunlight in the Arctic in April, May, September, or October? Here’s a clue, there is. The spring time sea ice extent hasn’t changed much in the satellite era but the summer and fall sea ice extents have changed. I think this would skew their results.
Not really. At the edge of the Arctic sea ice – which is ALWAYS above the Arctic circle, there is very little solar radiation through most hours of the day during most of March and September and all of October, and obviously none at all when the sun is below the horizon, and when the sun is above the horizon, it is not very high – many days even at noon, the sun looks like the hour before sunset in the mid-latitudes.
I can’t figure why the writer and these “scientists” exclude May though. It’s pretty high up for many hours of the day even by mid-April, and obviously even higher through the whole month of May.
They have certainly done something strange : they have only looked at the Arctic, and ignored the somewhat larger Antarctic.
Looking at the Antarctic they might have to mention the much larger area of increasing albedo caused by increasing sea ice at much lower latitudes. That could lead to the conclusion that global albedo is increasing on balance, as well as net energy reflected, so why would they go there?
Willis, is that meant to be a fortieth of a watt per sq. metre? (0.025 W/sq.m)?
Stay feisty mate, you’re great!
I think you have to look at when Arctic receive sunlight and when it does not. The Northpole only have a Sun between 21 st of March and and 21 st of September. And a lot of radiation from Arctic is originally from Equator. Polar regions radiate more energy than they receive from the sun.
Thanks, Santa … but why would you want to throw away three quarters of your data? How does that help you? Heck, even at the North Pole, with six months of light, you’re throwing away half the data if you only use three months. That only hurts your accuracy.
w.
As I see it, both points of view are relevant.
There is no incoming direct solar energy in the winter months, so the albedo and how much solar is absorbed/reflected during these months is wholly irrelevant. There is nothing to absorb, nothing to reflect.
In the Spring and Autumn, even if solar is absorbed (not reflected) it is weak. It carries little energy due to the low grazing angle and the fact that it has to pass through so much atmosphere, in addition the day is relatively short (particularly at the beginning of spring, and the end of autumn).
It is only in the summer period where there is some power in the sun, and of course the day is 24 hours, so this is the critical period on all acounts; the sun at its highest with greatest energy, the day at its longest, it is the period when the difference in the reflective index between ice and open water becomes most critical since at low grazing angles (spring and autumn especially early in the day and late in the day) open water reflects a great deal of solar and therefore has a more similar reflective index to that of ice in any event.
But of course, as far as global warming is concerned, it is the net effect of 24/7 365 days a year that is important. But that said, dealling only with average conditions loses important and insightful information as to what processes are going on, and how nature works. One needs to examine very carefully what is happening during the day, what is happening during the night, and what is happening on a weekly basis as cycle procession continues and impacts upon the processes that are going on and the rate at which they impart and distribute energy.
. .
Because in the winter the reflected sunlight will be ZERO from both the surface and clouds. Winter is the best time to study the effects on OLR when there is no sunlight. In fall and spring, reflectivity will depend on the changing sun angle. Thin ice crystals in clouds tend to be parallel to the surface and will reflect most of low angle sunlight. This effect is expected for the ice covered surface as well but less sunlight reaches the surface because the clouds have reflected it. All of this complicates trying to do an energy balance. At what angles are they measuring reflectivity? Vertical reflectivity measurements at the poles may be rather meaningless.
-0.025 W/m2/year * 14 years = 0.35 W/m2
========
How accurate is the data? Isn’t there a real risk that such a small change is simply due to noise or instrument drift?
Increasing the size of the sample would reduce the noise, thus by only using 3 months out of 12, the researchers increased the risk that their results are spurious.
fhhaynie December 18, 2014 at 6:10 am
fhhaynie, as I pointed out above even at the north pole you get six months of sunlight, and at the Arctic circle you get sunlight every day but one.
Which makes your justification of using a three month window invalid.
w.
richard verney December 18, 2014 at 2:11 am
As I see it, both points of view are relevant.
There is no incoming direct solar energy in the winter months, so the albedo and how much solar is absorbed/reflected during these months is wholly irrelevant. There is nothing to absorb, nothing to reflect.
No incoming only if you ignore the Auroral mechanism. Auroras are now known to be caused by the collision of charged particles (e.g. electrons), found in the magnetosphere, with atoms in the Earth’s upper atmosphere (at altitudes above 80 km). These charged particles are typically energized to levels between 1 thousand and 15 thousand electronvolts and, as they collide with atoms of gases in the atmosphere, the atoms become energized. Shortly afterwards, the atoms emit their gained energy as light (see Fluorescence). Light emitted by the Aurora tends to be dominated by emissions from atomic oxygen, resulting in a greenish glow (at a wavelength of 557.7 nm) and – especially at lower energy levels and at higher altitudes – the dark-red glow (at 630.0 nm of wavelength). Both of these represent forbidden transitions of electrons of atomic oxygen that, in absence of newer collisions, persist for a long time and account for the slow brightening and fading (0.5-1 s) of auroral rays. Many other colors – especially those emitted by atomic and molecular nitrogen (blue and purple, respectively)[1] – can also be observed. These, however, vary much faster and reveal the true dynamic nature of auroras.
As well as visible light, auroras emit infrared (NIR and IR) and ultraviolet (UV) rays as well as X-rays (e.g. as observed by the Polar spacecraft). While the visible light emissions of auroras can easily be seen on Earth, the UV and X-ray emissions are best seen from space, as the Earth’s atmosphere tends to absorb and attenuate these emissions. http://www.plasma-universe.com/Aurora
How much are we talking about in the all sky incoming / outgoing? The 12/9/14 values were bouncing between 33 and 40 GW according to http://www.ngdc.noaa.gov/stp/ovation_prime/data/2014/12/09/20141209_0800_north_forecast_aacgm.png & http://www.ngdc.noaa.gov/stp/ovation_prime/data/2014/12/09/20141209_1135_north_forecast_aacgm.pdf
“in addition the day is relatively short (particularly at the beginning of spring, and the end of autumn”
Definitely wrong. All of the Arctic, from the Polar Circle to the Pole has more than 12 hours of daylight from March 21 to September 21. By late May it is literally never dark anywhere in the Arctic, not even close to the Arctic Circle since the sun is only just under the horizon even at midnight.
If you are looking at an energy system, trying to determine if there is a net gain in the system, you don’t only look at the times when the system is taking in energy, do you? Don’t you have to look at the times when the energy is being lost as well? If I was looking to see that the Arctic was gaining total energy, which I would guess the basic purpose of a study like this would be, then I would have to look at the total package to actually see if there is a net energy change. I agree with Willis because without looking at the times you are losing energy, you can’t determine if you are gaining total energy, thus creating “warming.,” If you only look at the warmest months, when energy uptake is the highest, you are only trying to enhance the “warming appearance,” not trying to determine id the system is gaining energy. This study seems to be intended to find a way to show that there is “warming” ongoing, when, in fact, it can’t be found.
AO and NAO, Arctic an North Atlantic Ocillation?
Willis, isn’t the thinking likely to be that the big concern or signal is for the arctic summer ice extent? And therefore that’s the period of interest wrt albedo? I wonder if you could clarify or extend your attack on the justification for using just the summer months, since that is the period where albedo is significant compared to the winter which surely isn’t?
It would be interesting to see the same analysis but over the period they used. It may not matter, in fact I can’t see why it should, since you could incorporate all months for ease calculation because the dark months shouldn’t make any difference anyway. But then you can’t be accused (incorrectly) of making apples/oranges comparison.
The arctic receives sunlight throughout the year, every single day, with the possible exception of a moment in time, the winter solstice when the entire arctic above the arctic circle is cast in earths shadow. The three months proceeding summer receive the same amount of sunlight as the summer days. Certainly the days surrounding the winter solstice do not have much sunlight in the arctic, but those 3 months of spring have the same amount of sunlight as the 3 months of summer, so why aren’t those months important ?
” those 3 months of spring have the same amount of sunlight as the 3 months of summer”
Really??? well, there is some new discovery no one has claimed yet. Are you up for writing a paper on this? Nobel Price awaits you.
In Barrow Alaska the sun is below the horizon from November 19 to January 22. I’m not sure what you are saying about Arctic receiving sunlight every day.
there are other places in the Arctic that will see the sun on some days between November 19 to January 22. They would have a lower latitude than Barlow, but still be within the Arctic circle.
Agnostic December 18, 2014 at 12:03 am
Well, you kind of answered it yourself:
In fact, I’m not comparing anything. I’ve done a very different and encompassing analysis. They’ve improperly made an analysis of a partial dataset. I’ve shown the entire dataset. However, the other months are not “dark months” by any means. Even at the north pole itself you get six months of light, and there’s more further south.
In fact, the use of June, July, and August doesn’t even capture the months of greatest reflection. Those would be May, June, and July … and even April, May, and June have greater solar reflection than June, July, and August. All of which emphasizes the fact that it’s just cherry picking to use JJA.
In any case, I get a number close to theirs for the changes in those three months of JJA, a reduction of 4% in reflection… but so what? Obviously, thats being countered by increases in some of the other months. And at the end of the day, it’s the total effect that we’re interested in, not the effect in one month or a few months.
Finally, this is all a tempest in a teapot because the Arctic is only 4% of the planet. As a result, the change in W/m2 is trivially small by global standards whether its a 5% or a 1% change …
All the best,
w.
Willis, the question was not if it’s a tempest in a teapot if one looks at global scale! The question is the influence of the smaller albedo to seaice-extent in the arctic. In my eyes it’s not very clever to REDUCE the effect in unsing all month, also these with the reflection near zero due to the darkness. Anyway, you are right in one direction: also May is important, not only JJA. The albedo- difference of the open water to seaice for 70-80 degN is May: 37%; June: 48%; July: 47%; Aug.:34% (see: http://sun.iwu.edu/~gpouch/Climate/RawData/WaterAlbedo001.pdf ) and seaice albedo 0.5. In the end: I would mean the cherry picking was with you because the albedo effect is limited by nature to the month with solar input in a angle witch leads to biger differences between open water and seaice.
Frank December 18, 2014 at 1:53 am Edit
Huh? The scientists are claiming that this is an important phenomenon for the globe, that it’s a big factor contributing to global warming.
But it’s not. In fact it is a trivially small change in a minor part of the global energy balance.
w.
Willis,
A rarity in these parts. Given that the summer months are when the ice melts, and summer ice melt being the focus of the study, it stands to reason looking at net solar absorption during the summer months would yield up the most relevant trends.
May I quote you on that next time someone writes, “It’s really darn cold in Detroit this winter”?
Correct me if I’m wrong, but doesn’t Milanković theory work best when correlating summer insolation round about 65°N? Some land ice thereabouts has also got some folks wondering about implications for sea level rise. Just sayin’.
Much of the ice melts from underneath. Furthermore as far as extent is concerned, the ice begins its melt in mid March and ends 3rd week in September. Obviously, if we are considering the southernmost ice in the picture – it is reflecting sunlight in winter, too. Question, does it hurt to include it? If not, at least you marginalize criticism.
Gary Pearse,
Sure ice melts from below as well as above. In complex systems I think it’s entirely appropriate start off thinking in terms of all else being equal, what if we change x? Then go test that. Or in this case, what if x is changing? Let’s go see. Fundamental concept in empirical research.
The main thrust of my critique is directed at Willis’ implied charge that all else not being necessarily equal (and evidently not equal) is being ignored due to ulterior motives. These are additive/subtractive effects part of a complex dynamic system and nobody doing the actual research doesn’t know that.
In short, there’s a big difference between isolating an effect, controlling for other factors, picking out signal from noise — whichever metaphor suits — and visiting the cherry orchard.
It absolutely does NOT hurt to look at all the data. I see a lot of very good comments and questions in this thread on what else is happening year-round across the entire regional system. That’s brilliant stuff; needs to be done and quite interesting. My intent is not to marginalize criticism, but counter and rebut marginal criticism.
By all means, do the comprehensive analysis first, but then slice and dice — take a look at MAM and compare it to JJA … that’s a fantastic exercise. Now that I think on it, the first should be to take a look at JJA and attempt to duplicate the findings. At the very least that tells you that you’re at least looking at the same way the authors did. If you can show that, then going on to say, “now when I do this, something different from the story you’re selling happens” has a bit more meat on it.
“Even at the north pole itself you get six months of light, and there’s more further south.”
Doesn’t every point on Earth receive 6 months of sunlight (excluding shadow effects)? Just the distribution changes.
I have taken several statistics courses in the last few months — beginning with the one mentioned here previously. Some professors teach you how to eliminate all the data without the proper signal. Others refer to this as “cherry picking” or “data dredging”. I gather there are lots of ways to work the data over till you find the proper analysis. Perhaps your training is lacking these “advanced techniques”.
Just sayin’
there is a read danger in trying different analysis techniques until you find “the signal”. the danger is that what you find is simply an artifact of the technique.
Sort of like playing a recording backwards. It often will sound to the ear like the recording has actual words being spoken, when there cannot be. Charles Manson is a famous example. In this case, the signal is a spurious artifact of the technique.
you should always specify your analysis technique BEFORE looking at the data, to avoid the sort of bias the human mind unconsciously creates all the time.
All of which emphasizes the fact that it’s just cherry picking to use JJA.
=================
Why did the authors use JJA? The summer solstice is June 21 (approx) so if anything they should have used May, June and July. The 3 months when the sun is closest to the zenith.
Using June, July, and August means they used a data-set when the sun was not at zenith. So what is the justification?
Quick question regarding the lower panels of the top two graphs. The spikes – any idea what they indicate? Especially in the top two graphs, the spikes seem to be opposite to the slope of the blue line. When the slop is downward, the spikes are upward, vice-versa and are either upward or downward when the slope is about zero?
Is this simply a manifestiation of mis-alignments in the data of the upper panels? Or is there something else at work?
There also seems to be a peroidicity to the spikes…..
Well you do notice the dips in 2007 and 2012 when during the summer sea ice minimums,but seems to recover during the rebuild in 2013 and 2014.
.
Willis,
I’m curious about what is the W/m2 in your plots. Is it the daily average or daily max?
The numbers seem too high to be the average. But I presume you want the overall average to reflect changes in total energy for the year. So the max (if that’s what it is) would need to be weighted by the number of daylight hours in averaging.
Nick, while you’re here, I was wondering if you had any thoughts on area weighting as a factor especially at such high latitudes. It also occurs to me that masking iced areas vs. open water throughout the season is a necessary comparison … I wouldn’t think soot will make an impact on ocean regions.
“I wouldn’t think soot will make an impact on ocean regions.”
It has, Soot, dust or any other dark material has a very marked effect on the melting of sea and lake ice (and snow and glacial ice for that matter).
tty, agreed. Snippets I’ve read are that those things are stuff like plankton, silt, kelp forests which tend to keep sunlight from penetrating to depth, keeping the absorbed energy closer to the surface where it can more easily evaporate back out. My supposition here is that soot wouldn’t be much a contribution relative to other things, and any contribution it had wouldn’t be warming. My hope is Nick has a hint to toss into the mix, otherwise I’ll get around to chasing it down myself later.
Nick Stokes December 18, 2014 at 2:12 am Edit
Nick, like almost all such figures, they are 24/7 averages. These reflect the total amount of energy reflected over the month.
w.
How would such an analysis look in the Antarctic? 😉
I’m considering that question … not enough hours in the day.
w.
Willis
Personally, I consider even a monthly analysis too course a resolution. Conditions in the Arctic can change quite rapidly in a week, I would suggest that one has to perform an analysis of what is going on on a weekly basis. Thereafter, one may in some manner wish to integreate the results in to seasons.
In winter, albedo is an irrelevance since there is no direct solar to reflect, there is no direct solar to absorb.
In the Spring and Autumn, given the relatively low grazing angle of the sun, the reflective index of ice and open water is not so different, especially early in the day, late in the day, and especially early in the spring season, and late in the autumn season.
The difference in the reflective index between open water and ice is at its greatest in summer due to the greater grazing angle; the sun being higher in the sun. Further, it is during this period, that the sun shines 24/7 (subject to clouds). It is here where the albedo differences will result in the greatest changes in the amount of solar energy absorbed.
Of course, there is the balance whilst the ocean having less ice may mean that more solar is absorbed, it also means that more energy is lost from the ocean. The ice acts like a lid hindering the oceans giving up their energy to the atmosphere and thence out to space. When the ice melts and open water appears, the oceans can give up more of their energy.
Please correct me if I’ve got my figures wrong, but I’m wondering whether 0.35 W/m2 is really such a small figure as you suggest.
If an extra 0.35 watts of energy were delivered to the surface over every square meter north of the Arctic Circle (that’s about 20 million square kilometers) each year, that’s a total of 0.35 W/m2 x 31,563,000 (seconds in a year) x 2×10^13 (square meters) = 2.2 x 10^20 Joules of energy.
And if all that energy went into melting ice with a latent heat of fusion of 330.4 J/g, it would be enough energy to melt about 6.6×10^17 grams of ice, which I reckon is roughly 700 million cubic km of ice, which is about 10% of the ice has that remained in the Arctic at recent summer minima.
I’m not saying the extra 0.35 W/m2 would all go into melting ice. But the point is that 0.35 w/m2 is not a trivially small amount of energy as you claim. It is enough energy, delivered constantly over a year, to melt a very noticeable fraction of the Arctic’s sea ice.
Perhaps your heart is right to beat a little faster in this case?
As he stated, though, that’s a fluctuation of roughly 1% of the base-line incoming energy. If the water wasn’t freezing before, why would it suddenly become a glacial boondoggle?
Yes, it’s a lot of energy, as you mathed out, in aggregate. But then you apply that aggregate energy directly to grams of ice and consume them one after another to make a point of how much energy that is.
But, let’s scale this up: If you put a giant mirror around the sun and focused all of it’s outgoing energy, you’d destroy the earth. Perhaps your heart should beat faster because the end is near in this completely impossible and misused scenario? 🙂
Focused the outgoing energy _on the earth_
I agree entirely that my scenario in which all the additional energy that results from a change in albedo is channelled into melting sea ice is impossible. I said as much in my original comment.
My point is, however, that 0.35 Watts per square meter, even if it does only represent a 1% increase, is not a quantity of energy to be easily brushed off with a “be still my beating heart” comment.
Willis made the point in a recent WUWT post about plastic in the ocean that just because you can express an issue in terms of a very large number, that doesn’t necessarily mean it’s a very big issue. But equally, just because you can express an issue in terms of an apparently rather small number, that doesn’t mean you can dismiss it.
What a scientifically skeptical person might reasonably want to know is: how much difference might an increase of 0.35 W/m2 make to something that matters in the Arctic like, for example, melting sea ice? My calculations suggest that there is enough energy here to melt up to 700 million km3 of ice, which is a heck of a lot of ice. Dismissing that kind of long-term energy input with a snide comment seems inappropriate to me.
I agree entirely that it’s a lot of energy /in aggregate/. But as I attempted to point out, /in aggregate/ is an extremely useless figure in this case – and you are not focusing that energy to be able to melt the ice. (Also, note, it’s a DROP of .35w/sq m not an increase).
Take your own equation backwards: 330.4 j/g is what it takes to melt ice. Convert that to watts. It’s easy because Joules is watts per second. So that would become 330.4 watts per second per gram. Now, how many grams are in a square meter? Assuming that we are only talking about the planar surface (that would absorb heat directly from solar radiation) and assuming 100% absorption of the energy change (because easy mafs), and throwing in a wild guesstimate of how many grams that is (weight of 1 cubic cm is .92 grams and if we assume that the sunlight penetrates to 1cm, we can say that we have 10,000 cubic cm in a square meter – thus we can estimate we have 10,000 grams) – we have each gram having the incoming energy change by roughly 0.000035 watts per second per gram.
330.4 watts/second/gram >>> 0.000035 watts/second/gram
Nothing is going to freeze (Because this is energy dropped) and even if it were an increase, nothing is going to melt. It is simply too little of an energy adjustment to make a significant difference. And then you get into the actual amount of energy being retained by the ice (nowhere near 100%) and it becomes even smaller.
The energy fluctuation that this entails is too small to mean anything unless you extrapolate to a scale that doesn’t matter, which is why doing the energy change in aggregate isn’t worthwhile. As I said above – you created an impossible scenario: applying all of that aggregate energy to one gram of ice after another in serial instead of looking at how that energy is transferred to the earth. To apply a rule from biology: The dose makes the poison. Low levels of background radiation is fine (and some research suggests beneficial). Kissing the reactors at Chernobyl shortly after meltdown would have killed you. (I….probably still wouldn’t kiss them today. You know, in case you were in the neighborhood and decided to try.)
I do agree that a reference to what 0.35w/sq m would look like in the physical world would be handy. But it’s also something that would change based on where you are in the world (length of day being a chief driver of what it does to/for you).
The last time I checked, the Arctic is well below the ice generating temperature and conditions for most of the year. Try this, light a match in a walk in meat freezer for a few hours while monitoring the temperature recorded 10 feet from your match. Let me know how much the thermometer moves.
It’s good to remember that wind conditions in the Arctic have demonstrably greater influence on Sea Ice Extent than any of the satellite thermometer readings thus far…
The 0,35 W/m2 is for a period of 14 years not each year
Yes, so applied continuously over a period of 14 years, that’s enough energy to melt 9,800 km3 of ice which is more than the quantity that remains at the September minimum these years.
Nigel Harris-
6.6 x 10^17 gms of ice is 6.6 x 10^14 kg, or 6.6 x 10^11 tonnes of ice. Ice has a density of about 0.92 tonne/m^3, so that is about 7.3 x 10^11 m^3 of ice, or 730 cubic km of ice.
You were off by about a factor of a million, which can raise eyebrows, even in climate science.
However, it does work out to about 10% of the estimated Arctic sea ice volume at the September minimum, and about 3% of the estimated maximum Arctic sea ice volume in April.
Now the real question is- what is the net energy imbalance caused by uncovering Arctic ocean surface, allowing increased radiative, evaporative and convective cooling of the Arctic ocean? This change dwarfs the piddly 0.35 W/m^2 purported increase in absorbed solar insolation.
Ah yes, good catch! Sorry about the slip-up. Glad to see, however, that the rogue “million” inserted there doesn’t change my basic premise.
Naturally, there are many other, and possibly far more important, factors at play. But I’d repeat my basic point that 0.35 W/m2 should not automatically be dismissed as “piddly”.
Arsten’s comment of 7.38am (to which I seem unable to reply) seems very confused to me.
A watt is a joule per second. Not the other way round!
If an energy source of 0.35 W/m3 was applied as suggested in Arsten’s post entirely to the melting of the top centimeter of ice with 100% efficiency, it would take 110 days to melt it all.
Nigel Harris – This forum only allows nesting to 3 levels or so. Go up to the last “reply” you see and it’ll add it under that last one. 🙂
You were right, though, I confused the multiplication vs division in the description, though not in the calculations. w = J / s; J = w*s. Describing it gets confused. I should have just posted the math.
Actually a cubic kilometer of ice weighs about 0.92 x 10^15 grams, so it comes out as 700 cubic kilometers, not 700 million cubic kilometers. The latter figure is enough to cover the entire land surface of the Earth to a depth of about 4 kilometers. That’s what I call an Ice Age!
700 km^3 on the other hand equals a thickness of 3,5 cm over the entire surface of the Arctic. Not enough to increase my heartbeat.
Whoops
Should have read:
The difference in the reflective index between open water and ice is at its greatest in summer due to the greater grazing angle; the sun being higher in the SKY.
“So let’s start with the claim that the Arctic albedo has increased since the year 2000.”
Is that a typo? I thought they claimed decreased albedo? “The first is that there has been a five percent decrease in the summer Arctic albedo”
Just asking. Wouldn’t affect your analysis I think
And while I’m here, what’s with the large spikes in total reflection in the Spring? of 2001 (upward) and Spring of 2012 (downward)? Just noise?
And IIRC didn’t the sea ice cover crash rather abruptly in the Summer of 2007 then stay low for a number of years? I think this is the right chart http://www.arctic.noaa.gov/detect/detection-images/climate-ice-seaice-extent-trend-sep14.png Should I be able to see a correlation between that chart and the Ceres data because I’m having trouble doing so?
Don K December 18, 2014 at 2:39 am Edit
Thanks, Don. Fixed.
w.
The plotted time series data encompass cycle 23 peak to cycle 24 peak, with several months either side, is far too short. The upward spikes of 2000-2007, and mostly downward spikes of 2008 – 2014. Is this following the solar cycle or is it just a one-off correlation in this period? If they are correlated over multiple cycles, the question becomes, why? Mechanism?
With this short period, any attempt at conclusion is likely just spurious one way or the other. 10. or more cycles are likely needed for definitive conclusion but 3 or 4 would set clear boundaries on an answer. As these smoothed residuals plots look like random noise.
What this data does allow for is hypothesis generation to test predictions with future data. (model outputs are not data).
I am sure it is already done, but do these calculations take into account the shallow angle of the Sun & the extra thickness of atmosphere travelled through by the energy? I would have thought the additional energy passed on would be very small indeed.
I’m with Alan in that wonderation, how does the selective reflection of polarised light come into this. Its the glare (total reflection at very low angles?) we all know from visits to the seaside, swimming pools and driving on wet roads – also how rainbows work?
A satellite looking straight down won’t see the huge amount of light (glare) that bounces right off the surface of water at low angles and right under its nose. It’d be like measuring the albedo of a mirror, you’d get massively varied results depending where your light source is relative to your observation position.
Its all about Brewster’s angles, they gave me brain-ache during school physics classes.
The first point of interest is that the total amount reflected from the Arctic (Figure 1) has indeed decreased over the period at a rate of a quarter of a watt per square metre (-0.25 W/m2) per decade … for a total drop in absorbed (reflected?) solar of
-0.025 W/m2/year * 14 years = 0.35 W/m2
Typo, Bloke. Thanks, fixed.
w.
@ur momisugly Willis Eschenbach
“Albedo is calculated from the observations, it’s reflected sunlight divided by incoming solar.”
————
I’m curious as to how they do that with a polar (arctic) satellite given the constantly changing “equinox-to-equinox” angle of incidence (incoming) verses the angle of reflection (outgoing) … off of a highly irregular surface, to wit:
http://www.edu.pe.ca/gray/class_pages/krcutcliffe/physics521/17reflection/definitions/angle%20of%20incidence%202.bmp
Thanks Willis. This is an important question and it is good to have a complete set of actual data now. I’m tired of seeing cherry-picked timelines/seasons and made-up model data. We have expensive systems in space recording actual data and we should use them. I think the question on Arctic Albedo changes is answered now.
“Bright ice surface is not automatically replaced by bright clouds” also doesn’t seem to be true.
I thought I’d bring up something I’ve noticed about the interplay of reflective surfaces and clouds. It’s been my observation that large reflective surfaces tend to “burn off” thin cloud cover on partially sunny calm days. You can see this in satellite images over large lakes at times where there is a open cloudless hole right over the lake and thin cloud cover everywhere else. I attribute this to the lake reflections “burning off” the thin clouds. The clouds can’t keep their integrity when they are getting direct sun from the top and reflected sun from the bottom.
So under some Arctic conditions, I would think as bright ice drops it automatically burns off less thin clouds, or in other words, it APPEARS to be automatically replaced by bright clouds. But there is no actual replacement of clouds, just less clouds being burned off.
Arctic sea ice is holding up to global warming better than expected, according to the latest data from the CryoSat-2 satellite, a team from University College London will tell the AGU Fall Meeting in San Francisco.
Arctic sea ice volumes in the autumn of 2014 are above the average set over the last five years and sharply up on the lows seen in 2011 and 2012, according to the latest satellite data.
Data from the European Space Agency (ESA) CryoSat-2 satellite to be presented to the American Geophysical Union’s Fall Meeting in San Francisco later today (Monday 15 December, 2014) will show Arctic sea ice volumes in October and November 2014 averaging 10,200km3 – slightly down on the 10,900km3 reported in 2013 but sharply up on the lows seen in 2011 and 2012.
How many of the 12 3-month intervals have no sunlight to reflect from the clouds?. I know for a fact that in late December the sun doesn’t even shine at the north pole. Hard to call that a “cherry pick” as there is a good reason to exclude the months without sun shine.
why did they use june, july, august when the 3 months of greatest sunlight and May, June, July?
The region under discussion isn’t just the North pole but the Arctic. And the Arctic Circle is defined as “southernmost latitude in the Northern Hemisphere at which the sun can remain continuously above or below the horizon for 24 hours.” So some places in the Arctic Circle have no sunlight for only one day per year—on the December solstice—not months.
Ice goes along way south of the pole if its extent that is the subliminal subject of the study. You do get sunlight reflected off the ice in Hudson’s Bay, Labrador Sea, Bering/Alutians, Okotsk, North of Japan,
I am not understanding the ‘seasonal component’ in figures 1,2, and 3. Is Willis just creating an anamoly here and showing the steps? It is too early, where is my coffee.
Any chance to know if and how much albedo changed downsouth over Antartica? As far as I know sea ice is increasing there…
One could speculate and say that there has not been the soot- caused albedo change in the Antarctic because there is far less land mass with fewer inhabitants and less change in industrialization or human population in the Southern hemisphere.