Digital Diatribes

A presentation of data on climate and other stuff

Observations of a Skiing Actuary – Part 2

Posted by The Diatribe Guy on April 8, 2010

In the last post, Tony Crocker offered some insights into what he’s been seeing at a general level in his snow-tracking pursuits.   Here, I present some of the actual findings.

In e-mail correspondence, he clarified the calculations of the numbers and provided some additional thoughts.   While this isn’t a guest post, but a summary of our correspondence, all work is Tony’s and most of the pertinent observations come from him.

The Data

Tony has broken North America into 8 regions.   He used his own judgment in defining the regions, but in his words “My regional definitions are somewhat arbitrary (though most skiers would consider them reasonable), and the regions are big enough that within a region there can sometimes be some areas with good seasons and others with bad seasons in the same year.”  The regions are as follows:

1 – California

2 – Pacific Northwest

3 – Interior Canada

4 – U.S. Northern Rockies

5 – Utah

6 – Northern & Central Colorado

7 – Southern & Western Colorado

8 – Northeast

Within each of the regions, the data point is “Percentage of snowfall relative to normal.”  The final data point for the region is a straight average of all the observations in that region.   The Data is tracked as far back as 1970-71 season.   Some of the years 1970-75 had significant snowfall, but he excludes those years in some calculations.   The main reason for excluding the data is the low number of data points available.

Data Considerations:  (1) Spread of resorts within region could cause weighting issues which do not appear to have been considered; (2) number of resorts with good information can differ from year to year; (3) the expected snowfall will change from year to year as data is added, but Tony recalculates historical data to account for that.

Observations (1975-2009)

*Most variable region = California shows a standard deviation of 31%.   The most consistent, least variable, data is the Interior of Canada (15%).   Overall North America had a standard deviation of 13% over the time frame.

*The longest trend, including the less credible data of the early 1970s shows an overall trend from 1970 – 2009 of -2.9%.   However, Tony ran trends from 1972, 1975, 1982, 1987, and 1992 that were all positive.  The highest trend in overall North American snowfall, in fact, is since 1975, at +9.8%.

*Every single region has a positive trend since 1975.  Some regions show some negatives during the shorter trend time-frames.   The region with the largest trend is the Pacific Northwest, +21.1% since 1975.  But in a show of how volatile results can be, this same region actually has the largest negative trend back to 1970 because of high snowfall early in that decade.

*There is some significant correlation in snowfall between many regions, though not all.    It’s not necessarily surprising that the Utah and Colorado regions are very highly correllated.   Other areas of high correlation (over 50%)  are:  California/U.S. Northern Rockies; California/Utah; California/Southern & Western Colorado; Pacific Northwest/Interior Canada; Pacific Northwest/U.S. Northern Rockies; Northern Rockies/Utah; Northern Rockies/Both Colorado Regions.

*Negative correlation is indicated between: California/Canadian Rockies (most distinct negative correlation); Canadian Rockies/Utah; Canadian Rockies/South & West Colorado; California/Northeast.

Conclusions:

I asked Tony, based on his experience and observation, what are his main conclusions.  The following is his response:

1 – No trend in snowfall over the past 35-40 years in North American ski areas despite rising temperatures during most of that period.

2 – Rising temps don’t necessarily affect precipitation, but do affect the rain/snow line.  This is not yet an issue at almost any ski area in North America (Whistler base and Snoqualmie might be exceptions) but there are other ski regions of the world (Australia comes to mind) where it might be more serious.

3 – data is very volatile and it’s dangerous to claim trends based upon typical measuring periods like 5 or 10 years. 

Charts:

I’m providing three charts:  the overall North American chart, the California chart and the Pacific Northwest chart.   On the Pacific Northwest chart, keep in mind that from 1976 forward the trend is largely positive, but from 1971 forward it is negative.   California shows the volatility of the region, and the difficulty in being able to make grand assessments in the short term regarding snowfall and temperature.

North American Snowfall

North American Snowfall

California Snowfall

California Snowfall

pacific_northwest_snowfall

pacific_northwest_snowfall

Thanks for the information, Tony.

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9 Responses to “Observations of a Skiing Actuary – Part 2”

  1. […] Observations of a Skiing Actuary – Part 2 […]

  2. doug said

    I’ve followed Tony Crocker for some time on skiers websites, and he does a first class job. This sort of data is really important. I have seen people shy away from real estate at lower altitude ski areas on the belief they are doomed. I know of a member of the IOC who opposed granting the 2014 Olympics to Austria, because of a belief that the snow was becoming less reliable.

    Data. Wonderful stuff.

  3. R Shearer said

    I did my own field research today on the slopes in Colorado. As the season winds down the snow is still excellent.

  4. Mark T said

    Well, “still excellent” is really a misnomer… it was pretty bad until the last few weeks, and most of the northern mountains are still quite a bit behind normal for the year. Of course, by “quite a bit,” I mean like 50 inches out of 300 inches, not quite 17%, and the snow year is not done yet. They’ll probably all end up within 10% before the close of the ski season (next weekend or the weekend after for most resorts), and nearly average before it stops snowing.

    The shocker, of course, is Wolf Creek which is rather far behind considering that it has had several muli-feet days in the last two months. Also, if this year is anything like last, some big snows could wind up re-opening resorts. Aspen Highlands opened around Memorial weekend last year, for example. Very strange.

    Mark

  5. The Diatribe Guy said

    You guys are making me wish I knew how to ski. 15 years ago I started to learn, but then I blew out my ACL playing basketball and decided to forego skiing.

    As for precipitation, it’s no secret that we’ve been influenced by El Nino this year. Much milder in Wisconsin, as I expected, with much less of the stubborn snow. (Though we woke up with a blanket of it this morning) I am not exactly sure how Colorado and other areas are affected, but I imagine it would be an off year overall, given what I see here.

  6. Sera said

    I’ve been doing ‘field research’ on the east coast this year, and had a wonderful time. Much better than previous years (Sugar-Snowshoe). Broke down and bought a snowboard three years back (Cruzer), skis have been collecting dust ever since. Not bad for a 48 yr old. Pecip has been weird this year…

  7. Don B said

    Oregon’s Mt. Bachelor is at seasonal snowfall of 418″, which is above the average 387″ posted on their website. This continues the run of heavy snow seasons, the opposite of the prediction by Oregon State University profs a few years ago.

    http://www.mtbachelor.com/winter/services/snow_report

    http://oregonstate.edu/dept/ncs/newsarch/2006/Mar06/snow.htm

  8. woodNfish said

    This is interesting data, but you have to be aware of a few things:

    1. “Normal snowfall” is an arbitrary number and meaningless number. It is simply a convenient baseline to compare the data to.

    2. There is no proof that temperatures have been rising as Tony states in his comment 1.

  9. The Diatribe Guy said

    #8 – “Normal” here, I believe, is defined as the overall average. As I stated above, the baseline changes with new data and then the historical percentages change accordingly. No particular statement or agenda is hidden with that. Any time you want to look at deviations, you need to choose something. Average is as good as anything. More important are the trends, correlations, and volatility which aren’t affected by the baseline.

    I’m not an AGW proponent by any means, and I think I have shown here pretty convincingly that temps have been flat over the last decade or so. But I think most people would dispute the idea that temperature is not warmer today than in the 70s. There’s no statement by Tony suggesting an AGW connection, but there is proof of that. Leave Hansen and GISS aside, and the satellite data shows it.

    It doesn’t serve our purpose to dismiss evidence of warming. I maintain that it is real, but largely cyclical, and may well tie into sunspot activity.

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