Wednesday, 31 October 2007

Is the ski season changing?


Is global warming affecting the ski season? Evidence suggests that, so far at least, it has made little or no impact.
Last winter's miserable start in Europe prompted a predictable spate of unsubstantiated impressions and domesday predictions. The snow was arriving later than it used to. This was the beginning of the end for low resorts.

This was an opportune time to take a close look at the Ski Club's historical data in an effort to discover whether there were any clear indications that climate change was reducing snow cover. My conclusion was that unless last season's early drought represented some kind of tipping point, it was an isolated blip.

I looked average snow depths since 1993-4 at three stages of the season - the third weeks of December, January and March. The analysis covered a representative selection of over two dozen European and North American resorts. T

If there were any truth in the perception that the season was starting later, then logic dictates that early snow depth on the lower slopes would have fallen. But taking those slopes in isolation only a handful of resorts reported a reduction of more than one centimetre for the past four seasons, compared with average for the whole 14 year period. And remember that last December in many resorts was an unmitigated disaster.

To see whether there had been any overall, progressive reduction of snow cover I looked at the averages for three periods. The periods were 1993/4 – 1997/8, 1998/9 – 2002/3 and 2003/4 – 2006/7.

In the December week only five resorts had reported consecutive reductions for the three periods on both upper and lower slopes. They were mostly in the French Tarentaise and included Val d'Isere, Les Arcs and Meribel. Even so, one cannot conclude that those resorts are the first victims of climate change. They suffered starts just as dismal as last winter's in the 1993/4 – 1997/8 and 1998/9 – 2002/3 periods – and just one heavy early snowfall in the past four seasons would have improved the average for those winter's dramatically.

Two – Mayrhofen and Zell am See - showed a progressive increase, while Bormio, Selva Val Gardena, Zermatt, Avoriaz and Aspen all reported better average cover over the past four seasons than in the five Decembers starting in 1993/4.

A comparison of figures for the January week produced a similarly unclear picture, with no obvious general decline in snow cover and only in a handful of resorts were average depths significantly lower in the third week of March.

Confused? To see how inconclusive the evidence is, look at the following figures * for Kitzbuhel, Sauze d'Oulx, Val d'Isere and St. Moritz.

Kitzbuhel


Third week December
Third week January
Third week March
Average depth upper/lower slopes in the past 14 seasons

50/16

79/29

128/22
1993/4 – 1997/8
51/11
82/23
128/11
1998/9 – 2002/3
58/13
80/24
143/18
2003/4 – 2006/7
46/38
76/35
115/36

Sauze d'Oulx:


Average depth upper/lower slopes in the past 14 seasons
75/45

96/48
115/47
1993/4 – 1997/8
76/50
147/76
140/58
1998/9 – 2002/3
75/40
77/41
102/40
2003/4 – 2006/7
73/38
86/39
109/48

Val d'Isere

Average depth upper/lower slopes in the past 14 seasons

84/40

142/79

203/110
1993/4 – 1997/8
141/52
228/100
255/120
1998/9 – 2002/3
95/46
130/68
226/97
2003/4 – 2006/7
51/35
117/78
157/121

St. Moritz

Average depth upper/lower slopes in the past 14 seasons

104/31

127/49

131/42
1993/4 – 1997/8
105/31
134/58
115/25
1998/9 – 2002/3
121/28
143/52
157/68
2003/4 – 2006/7
69/31
95/36
109/45

Finally, two observations: first, even those cynics who harbour suspicions about the veracity of snow reports could hardly accuse resorts of doctoring trends.

And second: none of this is intended to deny overwhelming evidence of global warming or to suggests that it will not start to show up in future analyses. It is just to demonstrate the absurdity of many knee jerk reactions to last season's poor early conditions. Skiers deserve a more thoughtful approach.

*Depths are in centimetres and have been rounded up or down to avoid percentage points

This article appeared recently in Ski & Board magazine

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