Guest post by Steven Goddard
Several people keep asking why am I focused on winter snow extent. This seems fairly obvious, but I will review here:
- Snow falls in the winter, in places where it is cold. Snow does not generally fall in the summer, because it is too warm.
- Winter snow extent is a good proxy for winter snowfall. Snow has to fall before it can cover the ground.
So what about summer snow cover? Summer snow cover declined significantly (from the 1970s ice age scare) during the 1980s, but minimums have not changed much since then. As you can see in the graph below, the overall annual trend since 1989 has been slightly upwards.
Data from Rutgers University Global Snow Lab
Note in the image above that there has been almost no change in the summer minimum snow extent since 1989, and that the winter maximums have increased significantly as seen below.
Summer snow cover is affected by many factors, but probably the most important one is soot, as Dr. Hansen has stated.
The effects of soot in changing the climate are more than most scientists acknowledge, two US researchers say. In the Proceedings of the National Academy of Sciences, they say reducing atmospheric soot levels could help to slow global warming relatively simply. They believe soot is twice as potent as carbon dioxide, a main greenhouse gas, in raising surface air temperatures. … The researchers are Dr James Hansen and Larissa Nazarenko, both of the Goddard Institute for Space Studies, part of the US space agency Nasa, and Columbia University Earth Institute.
http://news.bbc.co.uk/2/hi/science/nature/3333493.stm
The global warming debate has until now focused almost entirely on carbon dioxide and other greenhouse gas emissions, but scientists at the University of California – Irvine, suggest that a lesser-known problem – dirty snow – could explain the Arctic warming attributed to greenhouse gases….The effect is more conspicuous in Arctic areas, where Zender believes that more than 90 percent of the warming could be attributed to dirty snow.
http://www.scienceagogo.com/news/20070506202633data_trunc_sys.shtml
In summary, winter snowfall is increasing and currently at record levels, and summer snow extent is not changing much. Earlier changes in summer snow extent were likely due primarily to soot – not CO2.
Why Is Winter Snow Extent Interesting?
Several people keep asking why am I focused on winter snow extent. This seems fairly obvious, but I will review here:
1. Snow falls in the winter, in places where it is cold. Snow does not generally fall in the summer, because it is too warm.
2. Winter snow extent is a good proxy for winter snowfall. Snow has to fall before it can cover the ground.
So what about summer snow cover? Summer snow cover declined significantly (from the 1970s ice age scare) during the 1980s, but minimums have not changed much since then. As you can see in the graph below, the overall annual trend since 1989 has been slightly upwards.
Data from Rutgers University Global Snow Lab
Note in the image above that there has been almost no change in the summer minimum snow extent since 1989, and that the winter maximums have increased significantly as seen below.
Summer snow cover is affected by many factors, but probably the most important one is soot, as Dr. Hansen has stated.
The effects of soot in changing the climate are more than most scientists acknowledge, two US researchers say. In the Proceedings of the National Academy of Sciences, they say reducing atmospheric soot levels could help to slow global warming relatively simply. They believe soot is twice as potent as carbon dioxide, a main greenhouse gas, in raising surface air temperatures. … The researchers are Dr James Hansen and Larissa Nazarenko, both of the Goddard Institute for Space Studies, part of the US space agency Nasa, and Columbia University Earth Institute.
http://news.bbc.co.uk/2/hi/science/nature/3333493.stm
The global warming debate has until now focused almost entirely on carbon dioxide and other greenhouse gas emissions, but scientists at the University of California – Irvine, suggest that a lesser-known problem – dirty snow – could explain the Arctic warming attributed to greenhouse gases….The effect is more conspicuous in Arctic areas, where Zender believes that more than 90 percent of the warming could be attributed to dirty snow.
http://www.scienceagogo.com/news/20070506202633data_trunc_sys.shtml
In summary, winter snowfall is increasing and currently at record levels, and summer snow extent is not changing much. Earlier changes in summer snow extent were likely due primarily to soot – not CO2.
“The 28 year trend in snow extent derived from visible and passive microwave satellite data indicates an annual decrease of approximately 1 to 3 percent per decade with greater deceases of approximately 3 to 5 percent during spring and summer. Precipitation in regions of seasonal snow cover appears to be constant or increasing slightly in some locations over the same time period, which suggests that diminishing snow cover is the result of increasing temperatures. One region where the snow appears to be diminishing rapidly is the Western United States, especially in spring when the duration of snow cover has been decreasing by 2-3 days per decade (see blue-colored areas in the Spring Duration figure). This satellite-derived trend agrees with direct measurement of snow depth and extent on the ground.”
Mote, P.W., A.F. Hamlet, M.P. Clark, and D.P. Lettenmaier. 2005. Declining Mountain Snowpack in Western North America. Bulletin of the American Meteorological Society 86: 39-49.
Maybe the last four years have changed the trend, but it seems like summer snow continues to decline.
“The alternative path (energy starvation) ends in economic collapse and subsistence living.”
Wrong on two counts: reducing CO2 emissions and other methods to reduce AGW are not an either/or proposition, and reducing emissions has never been shown to imply “energy starvation” or any of the other terrible consequences anti-mitigation alarmists posit without offering evidence.
[img]http://s4.hubimg.com/u/2255951_f520.jpg[/img]
Shoot, didn’t work. Summer snow extent through 2008. Significant decline.
You are certain it is soot that is causing the change in summer snow?
When I go to Rutger’s Global Snow Lab (which is an awesome site, by the way) the graphs it generates for me look very different than the ones Mr Goddard is using. Take a look for yourself:
Winter: http://climate.rutgers.edu/snowcover/chart_seasonal.php?ui_set=nhland&ui_season=1
I don’t see a trend. If it’s there it’s subtle.
Fall: http://climate.rutgers.edu/snowcover/chart_seasonal.php?ui_set=nhland&ui_season=4
A lot of variability. No trend I can see.
Spring: http://climate.rutgers.edu/snowcover/chart_seasonal.php?ui_set=nhland&ui_season=2
Now there’s a trend. Snow extent is way down.
Summer: http://climate.rutgers.edu/snowcover/chart_seasonal.php?ui_set=nhland&ui_season=3
Again, dramatically lower. 2008 is a record low; 2009 is the second-lowest.
The overall trend seems to be the reverse of what Mr Goddard is describing.
davidmhoffer,
My point is that winter snow cover has been extending towards lower latitudes over the last twenty years, which goes against the endless claims that snow cover is decreasing and storms are moving north.
I’m not definitely not trying to predict a long term climatological trend into the future.
Steve Goddard (16:09:58) :
The point is that since we have a longer data set, we have some idea of what the variability in that data set is. Given that knowledge, your trend is not distinct from the variability of the data. If you’re OK with that, then fine.
By the way, from the IPCC report,
[SCA = snow covered area]
“From 1915 to 2004, North American SCA increased in November, December and January owing to increases in precipitation (Section 3.3.2; Groisman et al., 2004). Decreases in snow cover are mainly confined to the latter half of the 20th century, and are most apparent in the spring period over western North America (Groisman et al., 2004). Shifts towards earlier melt by about eight days since the mid-1960s were also observed in northern Alaska (Stone et al., 2002).”
So decreases in wintertime snow extent are maybe not expected in North America, after all. You might have checked that first.
Leif: “This is a new Dark Age arising”:
I am astonished you should come to this conclusion based on the supposed (or even real) ignorance of participants at WUWT. Unless people here were 100% science literate, apparently we count as a rising hoard of barbarians. Yet scientists themselves display gross ignorance across disciplines – how’s your microbiology and understanding of PCR and the methods of genetic modification, for example? One does not expect specialists in one scientific feel to be able to address the esoteric and technical aspects of experts in another field. C.P. Snow lived too early – there’s a gulf between scientific disciplines let alone between the science community and non-scientists.
And yet here we find a blog which is engaging non-scientists in some of the most pressing questions created by scientists – and with good reason. The AGW CO2 theory has needed a good dose of skepticism from everyone, because, as has been well documented since Climategate, and was evident even before this — with examples of scientists losing their positions over failing to toe the AGW line — the ‘science’ has been dangerously tainted by the political advocacy of some of its most influential leaders. They have been allowing their science to be used to justify one of the most egregious attempts at grabbing and redistributing wealth from citizens bamboozled by expertise.
I’m not a scientist, I’m a historian of science, and I felt concern when the ‘scientific barbarians’ like Mann decided that they could massage a well documented historical phenomenon – the MWP – out of existence by superimposing various scientific proxies on top of the written record. Barbarism extends in many different directions, and one manifestation is to forget or deliberately obliterate the past for political or propagandistic purposes– and there is no denying that science was used in a propagandistic fashion by Mann. No matter how energetically Gavin is currently trying to rewrite the history of AGW propaganda on the MWP (and his own past proclamations), the fact remains that for nearly 10 years an important historical era and the quiet and professional work of many historians was being ignored and even ridiculed for ‘scientific’ purposes. But historians are evidently among the barbarians whose rising you fear, since we do not share all of your professional understanding. Insulted? You bet!
Incidentally, I am encouraged by seeing here at WUWT and elsewhere the greatest signs of amateur interest in science probably science the end of the era of amateur science at the turn of the last century. And bloggers here are generally justified in being sceptical in tone due to the arrogance and condescension with which their concerns have been treated by Mann, Jones, the IPCC et al in the past. Not a good idea to pour contempt on those you are perhaps trying to impress.
Sorry -several mistakes in last post: I meant to say:
Incidentally, I am encouraged by seeing here at WUWT and elsewhere the greatest signs of amateur interest in science probably SINCE the end of the era of amateur science at the turn of the last century.
“science” was on my mind!
REPLY: FYI, your last comment ended up in spam and was accidentally deleted with a bunch of viagra, I saw it sail by. You’ll have to try again, sorry,m Anthony
Leif Svalgaard (12:57:36) :
“…This is a new Dark Age arising.”
Leif – you may be more correct than you realise. The Dark Age at around about 450-700AD corresponds to “Bond Event 1”, the last Bond event, when apparently climate related migrations helped cause the fall of the western Roman empire. Bond estimates 1470 +/- 500 years between these cycles, which means we’re about due. (ref: Science v278, p1257)
Re the maximum NH snow extent, one possibly interesting correlation is land temperature vs snow extent (can’t be UAH series since data range needs to be over at least one PDO cycle). Everyone has been arguing about R^2, it might be interesting to see how correlated these variables are. If R^2 is high then we have ourselves a nice little feedback of humidity->snow->albedo correcting for increased solar W/m2 etc.
On the other hand I don’t see how the increasing Antarctic sea ice extent fits with this since sea ice doesn’t equate to snow.
Steve Goddard (16:27:25) :
“People who insist on doing a a linear fit or linear analysis across different legs of a cycle, are just not thinking clearly.”
You don’t have to draw the line through the entire data set. But if you pick a subsection, then you have to pass a higher statistical bar to reach significance. Otherwise, you cannot say your trend is different from the noise.
I could note that it warmed up a lot from 1996 to 1998. It’d definitely be a true statement. But I would not call it a trend.
By the way, I’m still looking for any signs that Hansen or anybody else was proclaiming that winter snow extent was decreasing over the US. Still haven’t found it. Do you have anything?
Larry Kirk (16:41:29) :
Could you clarify a bit on that thought of snow’s ability to reflect. Does that have to do with the fact that the thinner a surface is (low optical path length) the less emissivity it has? Read somewhere that emissivity is always stated for a surface of infinite thickness.
Is that the releated factor of snow crystals you speak of or something entirely different?
Fred H. Haynie (12:19:57) said “Much of the outbound longwave radiation from the top of the atmosphere measured by satalites is frozen cloud tops.”
I agree with everything else you said, but not this. Muchof the longwave measured by the satellites is radiated from low (unfrozen) cloud tops and clear sky. The higher and colder the cloud tops, the less longwave that they radiate. That’s why the IR satellite picture is in false color (e.g. http://www.ssec.wisc.edu/data/east/latest_eastir.jpg) showing bright white for cold cloud tops and darker colors for low clouds and no clouds. If they used real color, the high clouds of (e.g. thunderstorms and hurricanes) would not show up and the warm ground would, and the picture would be useless.
This is another reason why global warming is so heavily dependent on clouds, not snow on the ground, or CO2 in the air (esp in cloudy skies). The low clouds from GCR are hypothesized to radiate more IR to space and cause global cooling. Conversely high clouds radiate less and cause global warming.
Please find below an interesting (to me, if no-one else) breakdown of the growth in snow extent for each week of the year, using the full raw data set from the Rutgers snow lab.
This is hugely amateur effort, hacking around with Excel and probably statistically worthless, but it says to me that the eye is drawn to peaks in graphs, and not slopes.
I basically pivotted the data to plot the extent as a function of year for each week, giving me 53 series of data. I then used Excel’s linear trendline function to give me a gradient for each series (ie each week), and an R^2. The results are below.
What is telling is that there is a positive gradient only for weeks 1, 3, 4, 47, 48, 50, 51 and 52. Negative gradients (suggesting a reduction in extent over time) are found for every other week, and significantly steeper than positive gradients. Plot the “Increase per year” / “Week” data below to see what I mean.
My “analysis” (worth what you paid for it) is that the snow extent is falling for most weeks of the year. I have zero idea what implications that has, but I think it contradicts Steve’s interpretation that extent is increasing.
Anyway, source data, methods and results freely disclosed for peer review – I’d be interested in your comments.
Regards,
Dermot
Week,Increase per year,R^2
1,10840,0.00570
2,-15046,0.00790
3,5791.1,0.00140
4,5937.1,0.00140
5,-6092.6,0.00220
6,-37411,0.04000
7,-24899,0.01590
8,-24303,0.02450
9,-35498,0.04950
10,-72719,0.16240
11,-84099,0.19790
12,-66987,0.15870
13,-50607,0.06910
14,-56710,0.09580
15,-53113,0.10290
16,-79549,0.19180
17,-60042,0.11990
18,-75881,0.24170
19,-75959,0.21560
20,-48842,0.09170
21,-87189,0.24530
22,-77784,0.16670
23,-119080,0.33880
24,-106579,0.34560
25,-94858,0.30870
26,-86636,0.32810
27,-100677,0.51870
28,-75222,0.47350
29,-68542,0.48230
30,-61234,0.47860
31,-52238,0.39010
32,-35916,0.38450
33,-33119,0.27900
34,-27393,0.19950
35,-24235,0.14650
36,-9935.9,0.03700
37,-4007.6,0.00240
38,-1610,0.00010
39,-18059,0.00830
40,-35353,0.02590
41,-48776,0.03750
42,-51209,0.02940
43,-28394,0.00950
44,-24769,0.00900
45,-16896,0.00530
46,-16282,0.00600
47,25341,0.01990
48,951.56,0.00002
49,-2583.7,0.00020
50,24562,0.01700
51,39445,0.04160
52,31345,0.03380
53? hmmm…
From the Rutgers website . . .
“Annual snow cover extent (SCE) over Northern Hemisphere lands averaged 24.4 million square kilometers in 2008. This is 1.1 million sq. km less than the 39-year average and ranks 2008 as having the 4th least extensive cover on record…”
“over the last two hundred years, snow cover has gone through many phases where it has increased and many where it has shrunk. People who insist on doing a a linear fit or linear analysis across different legs of a cycle, are just not thinking clearly.”
Does the analysis of this data give us insight into any possible causes for these cycles? That seems to be the truly important thing here- I’m sorry if someone has already offered a possible explanation, I must have missed it.
So yeah, why the big dip between 1967 to 1988, as Wayne describes above for instance? Or from another perspective, by looking at the whole data, I can kind of make out a cycle of about a decade in length, a rise for 5 years, then a dip for 5 years. I’ve no idea if this is significant of anything or not. Given the limited data, we obviously can’t say much about any larger cycles that may be occuring.
As you say, we need to get a handle on these cycles. That would presumably come first- before we start beating each other over the head over whether what we are seeing is significant in terms of (A)GW, or not.
Lief I really do not see what your point is. And I do not think you understand the meaning of R^2 for the trendline in this case. Basically it would mean how well does your trendline fit the data and you can see visually the trendline is flat. Thats why you graph because the eye can tell you what is probably correct.
I let you off when you made a blunder re black bodies, also about CO2 freezing out of the atmosphere. But you are getting insufferable. If you do not have a point keep quiet, just let it go.
davidmhoffer (13:24:07) :
My recollection is that a photon has no mass so can’t transfer any kinetic energy?
A photon has momentum so can give you a kick = increase your kinetic energy.
David Middleton (13:28:38) :
If I draw a linear trend-line through less than one full cycle of a sin wave with no underlying secular trend, I get an R^2 of 0.88…
Indeed, and you also get a spurious linear trend. However, if people start out by claiming there is a trend, then they have forfeited the wave.
Bruce (15:51:16) :
Leif: “This is a new Dark Age arising”
Do you mean the one where most people no longer trust scientists
No, I do not mean that. I mean that people believe in pseudo-science, which can well be peddled by some scientists [iron suns, plasma universes, intelligent design, astrology, young earth, etc]
vigilantfish (17:19:22) :
Not a good idea to pour contempt on those you are perhaps trying to impress.
This is not about ‘impressing’ anybody. The Dark Age crowd are not trying to learn anything or skeptical, they are pushing [hard] an anti-scientific view of the world and are learning-resistant.
When the planet warms, the atmosphere can hold more water vapor. But both specific and relative humidity have been steadily declining: click1, click2
While we’ve seen some record snow this winter, we’ve also seen record tropospheric temperatures. Februrary continues on the same track following in the footsteps of a record January. See:
http://discover.itsc.uah.edu/amsutemps/
For the latest. Note especially sea surface (which is NOT ocean temps) up to 25,000 feet or so. Some of us have pointed out that warm temps and more snow go hand in hand in the winter, just as the very cold Antarctic region is also one of the driest regions in terms of precip. I maintain that yes…this has been a snowy winter, and the warmer tropospheric and ocean temps are to thank.
carrot,
I’m writing up a piece about this study from Columbia University, which predicted major declines in winter snow cover, starting in about 1990.
http://www.eee.columbia.edu/research-projects/water_resources/climate-change-snow-cover/index.html
I’m arguing with Tamino about these same issues at his blog (and he’s being a little rude to be perfectly honest).
It is not cherry picking to say that since 1989, snow extent has been increasing. From the graphs at Tamino’s blog, it appears snow extent decreased from 1970 to the mid-90’s and then began increasing until the present. Fitting a single line to all the data does not help anyone understand the variation of snow extent. In fact, centered around the mid-90’s, 15 of 16 snow extents were below the forty year trendline. A second-order polynomial fit would likely result in a higher R^2 value.
Leif Svalgaard (18:29:51) :
davidmhoffer (13:24:07) :
My recollection is that a photon has no mass so can’t transfer any kinetic energy?
A photon has momentum so can give you a kick = increase your kinetic energy>
no Leif… you have photons confused withy photon TORPEDOES. They haven’t been invented yet.
Steve Goddard (17:12:30) :
I’m not definitely not trying to predict a long term climatological trend into the future>
Didn’t mean to imply that you were. Was just wondering what you (or anyone else) thought as to cause/effect re warmer temps and snow extent increasing and sliding toward equator.
Fellow thinkers,
We must be careful not to fall into the trap of using inadequate statistics derived from incomplete data, ignoring other inadequate statistics derived from incomplete data that may (or may not) have a bearing on the subject, because of preconceived ideas.
I quote an apocryphal story, told to me by my father, told to him by his father who got it from his brother who was in the B.E.F. 1914/15.
When the British army first started issuing tin hats (all right chromium/molybdenum steel helmets) in 1915 there was resistance by the higher authorities on the grounds that “Real soldiers have never worn helmets, in their experience”. This ignored the historical evidence and even that some cavalry units (from which many of the senior officers were drawn) wore helmets. Shortly afterwards hospital returns showed a large increase in head wounds being treated. This was cited as evidence that helmets were not only not needed but were dangerous. It was proposed that steel helmets be withdrawn! Further investigation showed that the number of deaths from head wounds had decreased more than the increase in number of treated head wounds, and of those treated the head wounds were in general less severe than before the introduction of the helmets.
Fortunately for many concerned the steel helmets continued to be issued and saved many lives.
The obtaining off complete evidence, and not partial evidence in isolation, negated possible catastrophic effects. Now where have I heard something similar? Perhaps the proposal to destroy the worlds economy for a religious and preconceived idea.
p.s. It was indeed fortunate for me, as my grandfather was invalided home in 1917 with a head wound, finally released from hospital in 1919, although much of the time was due to re-constructive and plastic surgery.
Hi Steve,
Perhaps I missed something, but you never did get around to explaining why you concentrate on winter snow? I’m at a loss. Is increased precipitation telling us something exciting about climate?
Thanks for the Northern Hemisphere annual snow plot. Wow! That’s quite the upward trend you’ve got rocketing away there. Woosh. Although to be fair, the sideways trend is rather more evident. Prey tell though: what is the margin of error on that thing?
And remind me, why did you pick 1989 is a start point? What was wrong with all the other years? What have you got against 1992 for example? Or 1985?