Snow

It wasn’t that long ago, back in 2000, that David Viner of the Climate Research Unit stated that winter snowfall in England will become “a very rare and exciting event”. He added that “Children just aren’t going to know what snow is.” His comments came on the heels of several very low-snow winters in England.


After heavy snowfalls in 2010 we were informed that global warming could lead to more winter snow:


The fact that the oceans are warmer now than they were, say, 30 years ago means there’s about on average 4 percent more water vapor lurking around over the oceans than there was, say, in the 1970s. Warmer water means more water vapor rises up into the air, and what goes up must come down. So one of the consequences of a warming ocean near a coastline like the East Coast and Washington, D.C., for instance, is that you can get dumped on with more snow partly as a consequence of global warming.

This year (2011) also saw heavy snowfalls, and we’ve heard:


Heavy snowstorms are not inconsistent with a warming planet … In fact, as the Earth gets warmer and more moisture gets absorbed into the atmosphere, we are steadily loading the dice in favor of more extreme storms in all seasons, capable of causing greater impacts on society … If the climate continues to warm, we should expect an increase in heavy snow events for a few decades, until the climate grows so warm that we pass the point where it’s too warm for it to snow heavily.

We’ve also heard:


It’s still cutting-edge research and there’s no smoking gun, but there’s evidence that with less sea ice, you put a lot of heat from the ocean into the atmosphere, and the circulation of the atmosphere responds to that … We’ve seen a tendency for autumns with low sea ice cover to be followed by a negative Arctic Oscillation.

So — what’s the real story?

First, let’s look at the actual data from Rutgers University’s global snow lab. I downloaded monthly average northern hemisphere snow cover as estimated by satellite observations. The raw data shows a very strong seasonal cycle, and to nobody’s surprise there’s more snow in winter and less in summer:

With a simple “boxplot” of snow cover by month, this seasonal cycle becomes evident:

It’s also evident that northern hemisphere snow cover tends to be lowest in August and greatest in January, although the single largest value on record occured in a February, of 1978.

We can remove the influence of the annual cycle by computing snow cover anomaly, the difference between a given month’s snow cover and the average for the same month, to see whether each month is above or below average for that time of year:

Now we have a clearer picture of the overall changes. There appears to be an overall decline, as indicated by the blue line, which is a linear regression fit to estimate the overall trend. The decline is statistically significant, so it’s not just an effect of statistical noise. However, a smoothed estimate (a lowess smooth, the red line) indicates that the long-term changes may not be simply linear.

But there’s no denying that the last two winters have had heavy snowfall in the northern hemisphere. We can confirm this by examining data for individual months. Here, for instance, are the snow cover data for Decembers:

The last two Decembers (2009 and 2010) have high (but not the highest) values, and the smooth fit (red line) suggests a possible upward trend, especially recently. However, linear regression gives a trend estimate which is not statistically significant. I also fit 2nd- and 3rd-degree polynomials, also with no statistically significant fit. So the December data could be just the result of random fluctuations.

January data have a similar appearance:

Linear regression still gives no statistically significant trend, but a quadratic (2nd-degree) polynomial is almost so. The “false-alarm probability” is 5.1%, which is so close to the standard cutoff of 5%, that one should consider the result to be meaningful (but not ironclad) evidence of a genuine pattern, a dip during the 1990s followed by recent increase.

The February pattern is also similar:

Again a linear regression gives no statistically significant result, nor does a quadratic (2nd-degree) polynomial. But this time a cubic (3rd-degree) polynomial fit is significant. Again, the pattern seems to be a dip in the 1990s followed by recent increase.

We can even combine Dec-Jan-Feb into a winter estimate, which shows a statistically significant response to a quadratic polynomial. The pattern is, as you might expect, a dip in the 1990s followed by recent increase.

Given these patterns in wintertime, how is it that the overall (all 12 months) pattern seems to be decline? It’s because there’s a definitely significant trend of decreasing snow cover during summer months. Here’s the data for June, July, and August:

All three summer months show a statistically significant decrease, as does the combined Jun-Jul-Aug summer snow cover. In fact the statistical significance of summer decrease is much stronger than that of winter changes.

What should we expect in the future? For long-term forecasts, I’m not content with purely statistical models. They’re fine for very short-term prognostication, one or even a few time steps into the future (depending on how smooth and steady the trend is, and how large the noise is). But to project the long-term changes, I’d like models that don’t just incorporate statistics, but have some phsyics to go with ’em.

What does the physics say? To have snow, you need two things. First, cold air — but not too cold. Second, you need moisture.

Global warming affects both. It increases temperature overall, which, all other things being equal, would lead to less snow. But we should keep firmly in mind that temperature changes won’t be uniform. It’s easily possible (and this winter, actually happened) that some regions will be colder while others are hotter. Especially if the heat goes to regions that are usually extremely cold, while cold penetrates to more moderate regions, that temperature change could favor an increase in snowfall. And that seems to be one of the factors in this year’s heavy snow cover.

Global warming also increases moisture content in the air. Not only is this very basic physics (Clausius-Clapeyron!), it’s actually been observed:

This factor, due to global warming, could definitely favor more winter snow.

So, the physics can go either way. Ultimately, global warming will become so extreme that I believe the warming will reduce snow cover, dramatically, throughout the year. But how long it will be before we reach that “ultimately,” I don’t know.

I would say that Viner’s comment about England soon wondering what snow is, was ill-advised. I also think that comments about global warming leading to more heavy snowfalls in upcoming decades are premature. The physical argument is sound, but I’d put it in the “tentative” rather than “definitive” category. But I acknowledge that climate scientists know more about the physics than I do.

I’d also say that much of the discussion from climate scientists has not been definitive. It’s clear that more snow is not inconsistent with global warming. But again, forecasting many years into the future requires more detailed knowledge of the process than I think we’ve yet acquired. As for forecasting based on statistical models, well, more than a few years out, I don’t trust ’em.

Two things, however, are abundantly clear. First, it’s quite correct that the recent heavy winter snow is not evidence against global warming. Second, that those in denial will continue to claim that it is.

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53 responses to “Snow

  1. Excellent post, once again–and I’m particularly glad to see that time series plot of RH–I’d looked for something like that, to no avail.

    Once typo–surely “Global warming affects both. It decreases temperature overall. . .” should read “increases temperature overall. . .”

    [Response: Thanks — fixed.

    BTW, the graph is of *specific* humidity (the actual moisture content of the air), not relative humidity. I think relative humidity has been pretty stable (but I haven’t seen hard data).]

  2. “. . . the graph is of *specific* humidity. . .”

    D’oh.

    I knew that, really I did.

  3. http://data.giss.nasa.gov/modelE/transient/Rc_jt.4.01.html
    you might want to check out the snow cover percent and zonal mean anomalies, there are above normal spots even into 2080’s

  4. Poor David Viner, having to live with his one slightly careless comment in a newspaper interview becoming immortalised not just in the sqeptic world but now in the reality-orientated universe as well.

    Still, I suppose he should be honoured that his one voice is taken to represent the whole of scientific opinion. But was anyone actually seriously saying this at the time? It always seems strange that this one quote should come up so often supposedly to represent scientific opinion of the time, but never any others. (I’m not suggesting you are doing this here, but it is how the quote is often used elsewhere.)

  5. Also interesting to see the relative area changes in winter vs summer – June/July snow cover has almost halved since the 1970s, and the area changes are also pretty large, decreasing 6 million sq-km in June (from 12 to 6 million sq-km) and from 6 to 3 million in July. By contrast the changes in winter are minuscule both in absolute and in relative terms – January is up perhaps 1 million sq-km (~47 to 48) from the 70s, and again in Feb (~46 to 47).

    Of course, summer extent is mostly due to how much snow doesn’t melt. Winter extent is mainly due to how far south snow storms form.

  6. David B. Benson

    It may be that global annualized relative humidity is decreasing:
    http://www.friendsofscience.org/assets/documents/FOS Essay/Climate_Change_Science.html#Water_vapour
    shows a plot from linked NOAA/ESRL site.

  7. What I’d expect is fewer bigger snowstorms. Monthly averages of snowfall don’t strike me as particularly interesting. What would be a graph of number of days with any snow and also most snow in a day for each year for a few temperate locations. It’s the biggest storms that are interesting for their impacts. Also they have a disproportionate effect on perceptions of how snowy it is.

  8. I thought the arctic oscillation played a big role in NH cold winters and snowfall. And that heat transfer from as yet unfrozen seawater may generate the higher arctic pressures that drive cold air masses southward.

  9. Nice post…

  10. Nice timely post, but I do have a concern.

    Snow cover extent is important, but I don’t think it’s a particularly good indicator of snow volume. Except for those areas on the edge of the snow/no snow boundary. In other words, it tells you about what the margins are doing not much about the “core”.

    I know there have been efforts to map snow water equivalent (SWE) with passive microwave remote sensing, but I’m not aware if this data has been summarized into a format that can be readily organized, assuming the data is readily available in any format.

    The future of agriculture in Canada’s Saskatchewan River and the USA’s Missouri River Basins will heavily depend on how much snow continues to fall in the next century. And that still leaves open questions about how reliable it will be: it won’t be particularly helpful if the temporal distribution of snow shifts toward more extreme events.

  11. LazyTeenager

    Tamino, this summary matches my own understanding very closely. Unfortunately i have observed that such a nuanced picture is not something that has much traction in “climate skeptic” land.

    I deal with the scoffing around the David Viner quote by pointing out that they do not know what time scale was being referred to in the quote. It was probably not the next 10 years, but more likely 50-100 years.

    What I find odd though is that over on WUWT people who claim to be professional meteorologists try to down play the effect of higher sea surface temperatures on humidity levels and precipitation.

    The rank and file are trying to push the idea that humidity has nothing all to do with precipitation and that the only factor is cold.

  12. I’m surprised by the figure on specific humidity. For some reason I imagined that it would take a lot of time for that water to get up into the atmosphere (and maybe to come out), but it seems to be pretty instantaneous — the 1998 El Nino and the subsequent La Nina demonstrate the short term variability.

    • The average residence time for water vapour in the atmosphere is about 7 days. The rainfall-evaporation interchange between the oceans and the atmosphere is by far the largest component of the hydrologic cycle. To a large degree, the global rate of precipitation is controlled by the rate of evaporation from the oceans, and the rate of evaporation from an open water body responds pretty strongly and quickly to temperature changes in the lowest layer of the atmosphere..

      • Thanks. With all the record deluges this year, I had convinced myself that somehow this was a culmination of a long term process. I’m sure I’ve heard/read that average residence time of H2O in the atmosphere was short. I suppose I imagined that the residence time was long for some parts of the atmosphere (perhaps in the upper atmosphere) where this greenhouse gas would have a larger radiative effect than its relative abundance would suggest. That is, almost all of the water vapour is in the lower atmosphere over warm parts of the globe; do water vapour trends elsewhere follow lock-step or are they somewhat independent, capable of longer residence times, and potentially distinct in terms of greenhouse effect?

  13. Do check out this recent study on the melt rate of artic permafrost and subsequent carbon/methane release expected during the decade of the 2020’s. Here is the url:

    http://nsidc.org/news/press/20110216_permafrost.html

  14. This is an important subject. Not so much the AO breaking down and wind pattern driving the colder air farther south. The big deal is we are getting the moisture. As long as we don’t get so much snow that it causes flooding and damage to crops let’s hope we keep getting it. We can get a good idea of water content by looking at what the weather stations are reporting it to be. Looking at NCAR one of the major problems we will have is drought. But it looks like the models may have underestimated the effects of increased moisture in the atmosphere. One can only hope.

    Lazyteenager. The amount of precipitation has more to do with specific moisture in the atmosphere. They seem confused about what cold they are talking about. Warm air holds more moisture, it is less dense so lighter than cold air. As cold air, or front moves into an area of warm air it slides underneath lifting it which cools it enough to condense out the moisture. Its not so much the mixing (which is more duck weather) but the vertical travel that cools it.

  15. Thank you for this post. Discussions of precipitation (rain, snow, hail etc) seem to be quite tricky.

    We don’t get a lot of snow in Australia. Rainfall is what is discussed down here and I find most discussions not very meaningful. For example, people sometimes refer to trends / lack of trend in the average annual rainfall for Australia, which has several climate zones. Also, I would imagine it is very difficult at the moment to calculate the total volume of precipitation of rainfall over a region. (Calculating volume of snow might be easier if it can be mapped in some way.)

    The intensity of precipitation is of interest, but even that doesn’t say a lot about total volume of precipitation given that rainfall is, by its nature, is not measured by area, it is only measured at a point – or several points – all of which will have different results. (AFAIK with today’s technology.)

    In terms of practical interest (as opposed to scientific interest) the main concerns relate to out-0f-season rainfall, lack of seasonal rainfall (drought) and floods. (This past summer many places here broke rainfall records because of intensity of rainfall and the fact that there was very intense rainfall on several occasions. Not because of a lot of days of drizzle.)

  16. The last line should read “claim that it is,” rather than “claim that is it.”

    [Response: Thanks. Fixed.]

  17. [edit]

    [Response: Gee, “todd,” you are actually Girma Orssengo. And now you are a “sock puppet.”

    You are banned from this site permanently. But it seems you’re not enough of a man to suck it up and take your lumps — you’d rather try to sneak in using slimy sock puppetry. Never darken our door again.]

  18. Ray Ladbury

    This phenomenon is a wonderful illustration of the sort of rich behavior you get in a physical with competing effects–the result can push one way in one regime and quite the opposite in another. In the end, Viner may be right, merely premature. At worst, he will be wrong.

    The denialists will, however, always be in the realm of “not even wrong”.

  19. Jeffrey Davis

    I remember the snowfalls of 1978 well– we’d just gotten married in January, and the widespread freeze gave us an extended honeymoon. There was also 4ft of frost here and virtually every pipe in the city broke. It has become MUCH warmer since the 70s.

    If the last two years are any indication, winter snows will be a function of the wind currents as much as temps and humidities.

  20. Rain.
    Maybe that’s what should be watched.
    Not just the overall amount of rainfall per season in general.
    But also the number and strength of rainfall events in areas known for snow.
    If memory serves me correctly, at the same time record snow was falling in Europe this winter, it was raining in Greenland.
    Which is more unsual?
    Are they both flukes, or is there a trend here somewhere?

  21. Timely, highly informative, and very well done. Can anyone comment on the cause of the dip in the 90’s? It shows up in all of the monthly data sets. Also, presumably the 60’s and 70’s era was colder and and had less moisture in the atmosphere than now, yet plenty of snow. Now wetter and warmer and still plenty of snow. Seems to contradict the notion that you need cold and moisture for a lot of snow. The summer numbers are all about the melting of winter snow, and is reflective of higher summer temperatures, not snowfall.

    • Rattus Norvegicus

      In fact, for a lot of snow you need moisture and temps just below freezing. Too cold and the atmosphere cannot hold enough water for heavy snow.

  22. One more point, living along the Maine coast, I know that big snows happen when a cold air mass is in place, and a storm brings moisture in from the ocean. Moist ocean air hits cold dry air and we get snow. Not because the air in place over land is moisture laden, it is not. It is cold and dry. It is the moisture from the ocean that creates conditions for a heavy snowfall. I think the cold/dry, moist/wet discussion is misleading. There will always be moisture available from the oceans to create snow, unless the oceans are covered with ice. So the colder it is, the more snow you will get.

  23. A number of the comments here focus on the amount of annual precipitation as of an increase in mean precipitation means more water will be available to meet human needs. This would be true if the only thing changing was the precipitation rate, but this is obviously not the case because the driver of all these precipitation changes is the expected significant increase in air temperature.

    At climateological time scales, the amount of readily available surface water is basically mean annual precipitation minus mean annual evaporation/transpiration. Because evaporation is so sensitive to temperature it is not at all clear if a warming world with increased precipitation means more or less available surface water for any given region.

    It is perfectly conceivable, for example, to have annual precipitation increase 10 to 20% at the same time that mean annual surface water runoff decreases by 10 to 20% (or even more).

  24. We have the same “problem” here in germany, with >a href=”http://www.spiegel.de/wissenschaft/mensch/0,1518,71456,00.html”>Mojib Latif being quoted “Winter mit starkem Frost und viel Schnee wie noch vor zwanzig Jahren wird es in unseren Breiten nicht mehr geben” ( There will be no more winters with heavy frost and lot of snow like 20 years ago in our latitudes”).
    With the last winters in Germany having a real lot of snow, though not with the usual allocaton, many pseudosceptics claim Latif especially and AGW in general disproved.

    • Ah, but the pseudoskeptics still lovingly refer to Mojib Latif as predicting cooling!

      Of course, we once again miss a time frame.

  25. Sorry, corrected Link:Mojib Latif

  26. The observed temperature-snowfall relationship varies quite a bit with geography and season. In a 1999 JGR article by Davis et al. on Canadian climatology, the authors concluded as follows. (A “positive snowfall temperature slope” in this discussion means that snowfall increased as temperature increased; negative means the reverse.)

    “Our results demonstrate that the climatological relationship between mean monthly temperature and snowfall is neither simple nor straightforward. However, the large spatial variation in this relationship is logical, based on factors related to topography and atmospheric circulation. Four primary groups emerge from our analysis:
    1. There is a group of high-latitude stations with positive snowfall-temperature slopes where snowfall is limited by low temperatures and thus low atmospheric moisture content.
    2. A second group consists of locations in southeastern Canada with large positive slopes. High snowfall totals here arise from the proximity of coastal moisture sources and conditions just cold enough to generate abundant snowfall.
    3. A third group consists of warm, low-latitude coastal stations along both coasts where slopes are negative. Here, snow is uncommon because of the lack of available cold air over a sufficient depth to produce snow.
    4. Finally, there is a group of “lee” stations east of the Canadian Rockies with small negative slopes. At these locations, temperatures dictate that slopes should be positive. However, the high frequency of warm, dry conditions associated with westerly winds and katabatic warming makes the snowfall-temperature relationship negative.”

  27. Peter Dimitrov,
    The article you linked to actually talks about permafrost melt by 2200, not 2020. It’s “equivalent to half the amount of carbon that has been released into the atmosphere since the dawn of the industrial age.” However that article strengthens my opinion that the C cycle feedback is more likely to be chronic than acute (in human timescales).

  28. B Buckner,
    I’ve been looking at AO/NAO/PNA and don’t see anything conclusive. The NAO went into a strongly +ve mode from 1989 to 1995, having a role in expulsion of Arctic multi-year ice through the Fram Strait. But it doesn’t tally with the periods of reduced snow cover shown in Tamino’s analysis.

    There is probably more than one factor involved, especially given that the data is for the whole northern hemisphere.

    FWIW I think Viner was justified in his statement about snow in England (a trend that wouldn’t be reflected in this NH wide data). However in recent years we have seen what have become unusual snow events. My money’s on the Arctic sea-ice linkage proposed by Overland. Cohen has done some very interesting work, but I feel he gets into a chicken-and-egg problem in citing Eurasian snow cover as the cause (reduced sea ice in Barents/Kara/Laptev may have lead to increased snow). That said as an examination of Winter 2009/10, and the mechanisms behind similar events, Cohen’s paper is required reading (IMO).

    Ref:
    Overland, As discussed by NSIDC and Jeff Masters.
    e.g. http://nsidc.org/arcticseaicenews/2011/020211.html
    Judah Cohen et al 2010, “Winter 2009–2010: A case study of an extreme
    Arctic Oscillation event.”
    http://web.mit.edu/jlcohen/www/papers.html
    More interesting papers by Cohen and associates there….

  29. “There will always be moisture available from the oceans to create snow, unless the oceans are covered with ice. So the colder it is, the more snow you will get.”

    I have to disagree, Mr. Buckner. First, lots of places are far from the ocean and don’t have the same dynamic as you experienced in Maine. Second, even there the air temperature will affect how much moisture can be brought in from those easterly gales–the colder the air over the ocean, the less moisture will be entrained, and the less snow will result.

    That said, I do know what you mean; the ‘clash’ of warm moist air masses with cold ones is a great recipe for blizzards. That’s generally what happens here in the Southeast, too; the frontal boundary between a nice, moist system fresh from the Gulf of Mexico interacts with another off the northern High Plains, and hey presto! School cancelled for sure. . .

    But in a warmer future, more of that is going to end up falling as rain instead.

  30. That said, I do know what you mean; the ‘clash’ of warm moist air masses with cold ones is a great recipe for blizzards

    Exactly … the big nor’easters happen when relatively warm air picks up a lot of moisture off the SE atlantic coast and run north into cold air, typically over New England. As long as the air’s cold enough to chill the warm wet stuff enough to snow, rather than rain over New England, warmer SSTs and air temps over the atlantic offshore of the SE states will lead to more severe nor’easters. Helps build strong winds, too.

  31. Ray Ladbury

    B. Buckner,
    Your contention that colder equals more snow is simply false. All that is needed to get snow is wet air at a temperature below 0 degrees C. The amount of snow is determined by many factors–moisture content of the air, prevailing winds, terrain, weather (e.g. cold fronts) and on and on–all of which you’ve managed to ignore.

    I commend to you the words of H. L. Mencken–“For every complex problem, there is a simple solution–simple, easy-to-understand and wrong.

  32. I don’t have the data, just some anecdotes, bu I’d guess most skiers know that one gets bigger snow dumps when it’s cold enough, but not very cold.

    For instance, these are some examples from the CA Sierras. these are great … except it’s difficult to get to the ski slopes.

    We often ski near Kelowna, British Columbia. It gets plenty of of snow, but not usually such big dumps as the warmer Sierras.

  33. Ray Ladbury,
    Tamino’s piece is about the magnitude of snow cover or extent, not snow volume for any given storm event. Obviously, with colder air over land, the area subject to snowfall instead of rain will be larger. The rain/snow line moves south in colder temperatures, covering a larger area in snow after a storm. Yes, moisture content of the air, prevailing winds, terrain, weather (e.g. cold fronts), etc. will impact the amount of snow, and the snow amounts will vary from year to year based on these and other factors. But colder air in place over a larger area will result in more snow and less rain on average. How can this not be the case?

    • Ray Ladbury

      B Buckner,
      Dry air won’t drop snow no matter how cold it gets. And I disagree that the amount of snow doesn’t matter–a light snow will melt or sublime in a day, even when it’s cold.

  34. donaldbroatch

    It doesn’t usually snow in December in the UK Midlands. It did this year. We had extreme cold weather (coldest on record, I believe) so what we usually get as rain fell as snow (in fact, less, because precipitation for December was actually unusually low). What snow we got, stuck, but in fact there wasn’t that much- only about six inches. We didn’t get any snow after Christmas. I remember deep snow in the 80’s- after Christmas- lose your Wellies deep snow. Poor old David Viner wasn’t to know that changing weather patterns (possibly the result of global warming, reduced Arctic ice and high pressure in the Arctic, ironically) would bring Arctic cold to the UK and turn December rain to snow.

  35. A recent paper I reviewed at The Cryosphere by Brown and Robinson (2010) examines the March and April snowcover record “Northern Hemisphere spring snow cover
    variability and change over 1922–2010 including an assessment of uncertainty” . The statistical aspect puts this right up your alley. The most impressive change in the snow cover statistics is the increase in the melt off extent through time as measured from February-June. I have maintained that snow melt as reflected by snow cover extent loss, is a much better reflection of temperature than actual snow cover extent

  36. “But colder air in place over a larger area will result in more snow and less rain on average. How can this not be the case?”

    Easy. The area can already be below freezing, in which case you were already getting zero rain. Lower the temps and you’ll probably get less snow on average, which will then melt out faster when the season turns and temps rise again.

    I’d venture we’re probably seeing both effects this winter, with cold where it’s unusual (the English Midlands, say, as noted above) leading to more snow there via the effect mentioned, and (perhaps–I haven’t checked the snow data here, so this is officially a “Wild-Assed Guess,” or WAG) warmer temps in places like Nunavut leading to more snow there, too, via the mechanism of increased specific humidity.

    Now, off to check the Nunavut snow data and see if that’s true as speculated. . .

  37. the statistically significant slope of snow cover decrease seems to be around – 2 Mkm^2 for 40 years (although Tamino doesn’t give its precise value). This converts to – 5 Mkm^2 in 100 years, whereas the current snow cover is around 45 Mkm^2 , so a decrease of 10 % in 100 years. Is it really justified to announce anything for any children in any country ?

  38. Gilles all depends on the month. That is why the change in snow cover extent in winter has not been a point of focus in documenting climate change. The point of focus has been the very large changes from April-July in snow cover extent. A change in snowcover of 30-50% in the June and July periods noted above is worthy of note and concern.

  39. Let me pull out a chart that I’ve been doing for longer [not updated for past 2 seasons though], off from Rutger data and ask: What’s new? It’s blindingly obvious and would not be surprised if the Dec-Jan period would expand further, yet “snow off” moving earlier and earlier on the NH, AND steeper. This is going to seriously suck for farmers and later season water supply.

    Seasonal snow cover

    • To my previous post, I did add the SON and DJF periods since Rutgers had just posted those and also corrected for leap years to compute the seasonal average. Further added the quadratic values in the chart. For all intends and purposes, Sep-Nov and Dec-Feb are having a trend that’s flatter than Kansas.

      Suggestion for Tamino, maybe the OP could add October and November. The differences between NA, excluding Greenland and Eurasia differential are of interest for these months too. Generally for all main melt months, Eurasia is much stronger on the decline. So where is the main body of “Garden Window Denial”, Europe / Asia / North America?

  40. Major snow events are synoptic or sub-synoptic events. What drives a major Midwest Snowstorm or a series of European snowstorms are determined, however by global or planetary oscillations. I remember the majority of Northern Hemispher Winters (excluding Pinatumbo years) the last 20 years as being fairly mild. If there was precipitation it was rain. And in the case of New England blizzards that occiasonally cropped up, the majority of the snow was “wet snow” (ie just below the freezing level). Without a doubt, winters were quite mild in the Northern Hemisphere, and winter storm patterns generally followed changes in ENSO and the NAO pretty closely. In a warming planet, the Hadely Cell amplifies driving both the Northern and Southern Branches of the polar jet poleward. And with thier northerly migration, the energy that produces major snow events goes with them. And if the Northern Branch of the polar jetstream goes north, there is a fairly good chance that most winter storms (if they do in fact occur) will produce rain, sleet, mixed precip (that melts quickly). Water vapor content has little do with whether a region or hemisphere will have more or less snow. I think the predictions about snow made a decade ago had more to do with changes in planetary oscillation more than anything else. Yes, more water vapor could produce more precipitation; but it is snow we’re speaking of. And in a warming planet, the chances for droughts also increase for those areas more susceptible to droughts. The Great Plains States in the middle of the US, in a warming planet that is under the influence of an amplified Hadley Cell) would need to get its precipitation from the Subtropical jet. But the Rocky Mountains would act as a buffer to this mositure source. Droughts there would be normal under warming conditions. For Europe, precipitation in some instances would be normal. But a weakening of the NAO and amplification of the AMO could mean droughts for Southwest Europe, but above level precip for North Africa. It all depends on how the semi-permanent pressure systems play out. Remember, the Equatorial Pacific has abundent moisture; but, changes in the trade winds are the determining factor for precipitation there. It is not unusual for some parts fo the Pacific to see droughts under certain conditions not matter what the mixing ratio is. An Amplified Hadely Cell means large areas of the mid-latitudes would see subsiding air aloft, which acts as a cap to large scale rainfall events.

    Raw statistical analysis can provide perhaps many answers. But if it is divorced from atmospheric physicis, it could lead you down the wrong path.

    • Global “or” Planetary oscillations…. please do tell which these exactly are? My thumb is throbbing, a usual sign something is foul. Can you see the strong March-September declines?

  41. March 17

    Usually in the Spring the snow begins to melt on the SOUTH side of the street, this year is the opposite on the NORTH side?

    Is the EARTH screwed up??? Recent earthquakes?? Shifted the axis?? The beginning of the end …….2012??

    Alignemnt of Planets???

    Curious??

    Thanks

    M Lowell
    Ottawa Canada

    • Marc, are you at all serious?

      In “Snow Ste. Marie,” where I grew up, the north side generally saw more melt in the spring for the simple reason that it saw more direct sunshine. In my experience that’s usually the biggest variable, but there could be many reasons for your results to vary–puddling resulting in increased splashing on one side or another, snow removal activities or pavement salting that occurred unbeknownst to you, albedo alterations due to dirt that preferentially affect one area more than another, and so on.

      Just in case you are serious.

      ‘Cause the axis of the earth has nothing to do with it.

      • First time this year mowed the grass today and sure as heck the north side was denser and higher… but then the north side is just 30 meters away from the south side and the south side is lined by (mostly) evergreen trees ;-)

        Mind you, watching Baffin and the daily updated sat images of West Greenland and reports of there having been a spring experience for pretty much the meteorological winter, who knows… LoL

  42. Sounds about right; the south sides of streets tend to have these ‘buildings’ lining them, rather like your ‘mostly’ evergreens.

    But as you say–who knows?

    ;-)

  43. Advert… not a complete and partly possibly inaccurate description of snow/ice etc. winter related phenomena with some english translations…
    http://erimaassa.blogspot.com/2011/03/finnish-words-for-solid-h2o.html