The likelihood of holding outdoor skating marathons in the Netherlands as a policy-relevant indicator of climate change
H. Visser
A. C. Petersen
When I was born - in 1956 - the chance of realizing a Frisian Eleven City Ice Skating Marathon in Netherlands was 1 in 4. When my daughter was born - in 1999 - this chance had diminished to 1 in 10. An enormous change in one generation! This quote was taken from a speech by J. P. Balkenende, prime minister of the Netherlands. It illustrates how a seemingly odd indicator of climate change, the chance of organizing large-scale outdoor ice-skating marathons, can play a role in the public and political debate on climate change. Outdoor skating has a very strong public appeal in the Netherlands, and the diminishing chances of holding such events provide an additional Dutch motive for introducing climatepolicy measures. Here, ice skating marathons are approached from three angles: (1) the societal/political angle as described above, (2) the more technical angle, of how to derive annual chances for holding large-scale marathons such as the Eleven City Marathon ('Elfstedentocht'), and (3) the role of (communicating) uncertainties. Since the statistical approach was developed in response to communicational needs, both statistical and communicative aspects are reported on in this article.
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deforestation will continue for many years to come. We all know the pictures of
melting glaciers on Greenland and satellite images of the hole in the ozone layer.
An example closer to home: when I was born in 1956 the chance of realizing
a Frisian Eleven City Ice Skating Marathon taking place was 1 in 4. When
my daughter was born in 1999 this chance had diminished to 1 in 10. An
enormous change in one generation!
(From a speech of J.P. Balkenende, prime minister of the Netherlands,
June 6, 2005)
Climatic change is abound with uncertainty. Not only are uncertainties intrinsic in
the science; societal actors also have different opinions on what aspects of climatic
change constitute a problem and why. When analysts search for indicators to analyze
and communicate information about climatic change, they therefore have to address
both scientific and societal uncertainties. In this article, we report on the development
and communication of a new indicator of climatic change for the Netherlands.
The indicator is innovative in two regards. First, the Dutch public was informed
about a dimension of climatic change that directly appeals to them and that had not
been clearly communicated before. Second, a new statistical approach was developed
in order to be able to communicate robust messages about changes in this indicator.
Since the statistical approach was developed in response to communicational needs,
both statistical and communicative aspects of the new indicator are reported on
in this article. Both aspects or storylines meet in the Dutch prime ministers
quote above.
Outdoor skating is an extremely popular sport in the Netherlands, with a large
number of skating tours being organized throughout the country in the coldest winter
periods. The tour of all tours is the Elfstedentocht, the Eleven City Ice Skating
Marathon, held in the province of Friesland. Here we will explore from several
angles the likelihood (the annual chance) of an Elfstedentocht being organized.
This likelihood is considered to be a complex indicator of climate change, with many
uncertainties attached to it, but with a very strong public appeal too, providing an
additional Dutch motive for setting climate-policy measures.
Climate warming has influenced the conditions necessary for holding this outdoor
skating marathon since the beginning of the twentieth century. In this article, the
focus is on the evolution of the chance of holding an annual Elfstedentocht in the
period from 1901 to 2008.
For several reasons, estimating this chance indicator is more complex than
evaluating other climate indicators such as annual averaged temperatures, annual
total precipitation and drought frequencies. The chance of holding a marathon is
dependent on:
maximal ice thicknesses that are not measured routinely.
the amount of open water due to drainage or flowing under bridges.
organizational factors delaying the decision about whether to hold a marathon,
e.g. creating kluning (walking on skates) facilities, and mobilizing competitive
and non-competitive skaters.
Our approach here is to find an indicator calculated from standard meteorological
data from the beginning of twentieth century, and related to maximal ice thickness
in the province of Friesland. Clearly, this indicator should be homogeneous (i.e.
corrected for changes in instruments, location of instruments, changes to the instrument
by environment etc.). Finally, the annual chance for organizing the Elfstedentocht
is deduced from the chance of the ice-thickness indicator crossing a threshold.
Uncertainties play an important role in the evaluation of change in chances for
a skating marathon. These uncertainties need to be assessed and communicated. To
express uncertainty in statistical t (...truncated)