Effects of climate change on high Alpine mountain environments: Evolution of mountaineering routes in the Mont Blanc massif (Western Alps) over half a century

Abstract

In high alpine environments, glacial shrinkage and permafrost warming due to climate change have significant consequences on mountaineering routes. Few research projects have studied the relationship between climate change and mountaineering; this study attempts to characterize and explain the evolution over the past 40 years of the routes described in The Mont Blanc Massif: The 100 Finest Routes, Gaston Rébuffat's emblematic guidebook, published in 1973.The main elements studied were the geomorphic and cryospheric changes at work and their impacts on the itinerary's climbing parameters, determining the manner and possibility for an itinerary to be climbed. Thirty-one interviews, and comparison with other guidebooks, led to the identification of 25 geomorphic and cryospheric changes related to climate change that are affecting mountaineering itineraries. On average, an itinerary has been affected by nine changes. Among the 95 itineraries studied, 93 have been affected by the effects of climate change-26 of them have been greatly affected; and three no longer exist. Moreover, periods during which these itineraries can be climbed in good conditions in summer have tended to become less predictable and periods of optimal conditions have shifted toward spring and fall, because the itineraries have become more dangerous and technically more challenging. ARTICLE HISTORY

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Effects of climate change on high Alpine mountain
environments: Evolution of mountaineering routes
in the Mont Blanc massif (Western Alps) over half a
century
Jacques Mourey, Mélanie Marcuzzi, Ludovic Ravanel & François Pallandre
To cite this article: Jacques Mourey, Mélanie Marcuzzi, Ludovic Ravanel & François
Pallandre (2019) Effects of climate change on high Alpine mountain environments: Evolution
of mountaineering routes in the Mont Blanc massif (Western Alps) over half a century, Arctic,
Antarctic, and Alpine Research, 51:1, 176-189, DOI: 10.1080/15230430.2019.1612216
To link to this article: https://doi.org/10.1080/15230430.2019.1612216
© 2019 The Author(s). Published with
license by Taylor & Francis Group, LLC.
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Effects of climate change on high Alpine mountain environments: Evolution of
mountaineering routes in the Mont Blanc massif (Western Alps) over half a century
Jacques Mourey
a
, Mélanie Marcuzzi
a,b,c
, Ludovic Ravanel
a
, and François Pallandre
c
a
CNRS, EDYTEM, Université Grenoble Alpes, Université Savoie Mont Blanc, Chambéry, France;
b
Institut de Géographie Alpine, CNRS, PACTE,
University Grenoble Alpes, Grenoble, France;
c
École Nationale des Sports de Montagne/École Nationale de Ski et d’Alpinisme, Chamonix,
France
ABSTRACT
In high alpine environments, glacial shrinkage and permafrost warming due to climate change
have significant consequences on mountaineering routes. Few research projects have studied the
relationship between climate change and mountaineering; this study attempts to characterize and
explain the evolution over the past 40 years of the routes described in The Mont Blanc Massif: The
100 Finest Routes, Gaston Rébuffat’s emblematic guidebook, published in 1973.The main elements
studied were the geomorphic and cryospheric changes at work and their impacts on the
itinerary’s climbing parameters, determining the manner and possibility for an itinerary to be
climbed. Thirty-one interviews, and comparison with other guidebooks, led to the identification of
25 geomorphic and cryospheric changes related to climate change that are affecting mountai-
neering itineraries. On average, an itinerary has been affected by nine changes. Among the 95
itineraries studied, 93 have been affected by the effects of climate change –26 of them have been
greatly affected; and three no longer exist. Moreover, periods during which these itineraries can
be climbed in good conditions in summer have tended to become less predictable and periods of
optimal conditions have shifted toward spring and fall, because the itineraries have become more
dangerous and technically more challenging.
ARTICLE HISTORY
Received 6 September 2018
Revised 12 April 2019
Accepted 24 April 2019
KEYWORDS
Mountaineering; high
mountain itineraries; climate
change effects; Mont Blanc
massif
Introduction
Climate change led to a temperature increase of 2°C in
the Alps between the end of the nineteenth century and
the beginning of the twenty-first (Auer et al. 2007), with
a strong acceleration in warming since the 1990s (IPCC,
2014). In this context, and due to being very sensitive to
climate variations, high alpine environments have
undergone major change. The total surface area of alpine
glaciers decreased by half between 1900 and 2012 (Huss
2012; Vincent et al. 2017), while rock faces experienced
an increase in the frequency and volume of rockfall
(Geertsema et al. 2006; Ravanel and Deline 2011;
Ravanel et al. 2013,2017). These changes raise the ques-
tion of what the effects might be on recreational moun-
tain activities, and especially on mountaineering.
Mountaineers climbing during the summer months are
undeniably noticing important changes to the environ-
ment to which they must adapt by modifying their
techniques. Although awareness of this issue dates back
to the 2000s, only a few studies have been conducted to
confirm it—such as Behm, Raffeiner, and Schöner
(2006), Ritter, Fiebig, and Muhar (2012), Bourdeau
(2014), Temme (2015), and Mourey and Ravanel
(2017). As such, the evolution of mountaineering itiner-
aries due to climate change remains poorly documented.
This article aims to describe and explain the evolution—
over nearly half a century—of mountaineering itineraries
in the Mont Blanc massif (MBM), the birthplace of
mountaineering and still a major mountaineering desti-
nation (Modica 2015).
However, it is impossible to document all mountai-
neering itineraries as several thousand have been climbed
in the MBM. The 1975 Vallot guidebook—The Mont
Blanc Massif, Aiguille Verte–Triolet–Dolent–Argentière–
Trient (Devies and Menry 1975)—which lists the routes
in each glacial basin with a detailed description, includes
747 itineraries. Hence, our study focuses on the itiner-
aries in Gaston Rébuffat’sfamousguidebook,The Mont
Blanc Massif: The 100 Finest Routes. Using recent guide-
books and interviews, the itineraries described by
CONTACT Jacques Mourey jacques.mourey@univ-smb.fr CNRS, EDYTEM, University Grenoble Alpes, University Savoie Mont Blanc, Chambéry 73000, France.
ARCTIC, ANTARCTIC, AND ALPINE RESEARCH
2019, VOL. 51, NO. 1, 176–189
https://doi.org/10.1080/15230430.2019.1612216
© 2019 The Author(s). Published with license by Taylor & Francis Group, LLC.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted
use, distribution, and reproduction in any medium, provided the original work is properly cited.

Rébuffat in 1973 were compared with their current state.
First, the geomorphic and cryospheric changes that have
affected the area were identified; then, for each itinerary,
the specific changes that have affected it were established
and also the degree to which these changes have changed
the climbing technical level and danger. The evolution of
the manner in which mountaineers tackle these routes
due to the effects of climate change will then be dis-
cussed, along with the consequences for the popularity
of mountaineering.
Study site
The MBM the birthplace of mountaineering, which
is being strongly affected by climate change
Mountaineering originally developed in the western Alps,
and especially in the MBM, at the end of the eighteenth
century (Hoibian 2008). Since then, it has evolved con-
siderably through technical (Duez 2009), cultural and
ideological changes (Hoibian and Defrance 2002;
Bourdeau 2003). The “Golden Age”of mountaineering,
whose 150th anniversary was celebrated in 2015, is con-
sidered to start in 1854 and end in 1865 with the first
ascent of the Matterhorn (Switzerland). It was marked by
a series of important first ascents, most notably those
made by Edward Whymper and his guides in the MBM.
In 2018 Chamonix (France) and Courmayeur (Italy)
applied for mountaineering to be included on
UNESCO’s Intangible Cultural Heritage Lists. Over the
past 200 years, the evolution of mountaineering has been
mainly due to socio-cultural reasons (Hoibian and
Defrance 2002;Bourdeau2003). However, the current
changes tothehigh mountain environment due to climate
change is challenging accepted mountaineering practices.
The MBM (Figure 1) is located in the north-western
Alps between Switzerland, Italy and France, and covers
550 km
2
. About 30% of its surface is covered with ice
(Gardent et al. 2014), with some 100 glaciers –includ-
ing the Mer de Glace, the largest glacier in the French
Alps, with an area of 30 km
2
. A dozen peaks exceed the
altitude of 4,000 m a.s.l., including Mont Blanc, the
highest summit of the Alps at 4,809 m a.s.l.
The MBM presents a cross-range asymmetry. Six of
the largest glaciers of the massif are located on its
north-western aspect, where slopes are gentler than on
its very steep south-eastern aspect, which is character-
ized by small glaciers bounded by high subvertical rock
walls. This asymmetry implies different climatic con-
texts. In Chamonix (1,044 m a.s.l.), the mean annual air
temperature (MAAT) is +7.2°C, while in Courmayeur
(1,223 m a.s.l.), it is 10.4°C. At the Aiguille du Midi
(3,842 m a.s.l.), the MAAT is −8.2°C (reference period:
2008–2010, Météo-France data). In Chamonix, MAAT
increased by 1.7°C between 1934 and 2009. It is impor-
tant to note that this warming mainly affects winter
temperatures (Durand et al. 2009); these increased by
2.8°C compared to summer temperature, which
increased by 1.5°C (Météo-France data). Moreover,
MAAT increased four times faster over the period
1970–2009 than during the period 1934–1970. The
MAAT also increased at high elevations: above
4,000 m a.s.l., it increased by 1.4°C between 1990 and
2014 (Gilbert and Vincent 2013). Since 1990, the MBM
has experienced seven summer heat waves (in 1994,
2003, 2006, 2009, 2015, 2017 and 2018). In France,
summer 2018 was the second hottest summer since
1900 (2003 was hotter). In Chamonix, the average
annual precipitation is 1,288 mm. In Courmayeur, it
is 854 mm. At 3,500 m a.s.l., precipitation is three times
higher than in the town of Chamonix (Vincent 2002).
Since the end of the Little Ice Age (LIA), precipitation
levels have experienced little change; however, there has
been a clear decrease in snowfall days relative to total
precipitation days (Serquet et al. 2011) and there is
more frequent and intense melting (Klein et al. 2016).
Consequently, in the Swiss Alps between 1,139 and
2,540 m a.s.l., snow cover duration shortened by
8.9 days/decades
−1
during the period 1970–2015, with
a snow season starting 12 days later and ending 26 days
earlier than in 1970 (Klein et al. 2016). While these
changes in snow cover are elevation dependent, and
less pronounced at higher altitudes (Durand et al.
2009), snow quantity at high altitude is also decreasing.
With higher and faster warming at high altitudes than
the global average (Beniston 2005;Aueretal.2007), climate
change is causing substantial change to high mountain
environments. In the MBM, the glacial surface area
decreased by 24% between the end the LIA and 2008
(Gardent et al. 2014), with a considerable increase in the
acceleration of melting since the 1990s (Huss 2012;Vincent
et al. 2017). Mean glacier mass balance in the European
Alps was −0.31 ± 0.04 m w.e.a
−1
during the period
1900–2011 and −1mw.e.a
−1
during the first decade of
the 2000s (Huss 2012), which illustrates the acceleration of
glacial shrinkage. In the MBM, the region-wide mean mass
balance was −1.04 ± 0.23 m w.e.a
−1
between 2003 and 2012;
theArgentièreglaciermeanmassbalanceoverthesame
period was −1.46 ± 0.4 m w.e.a
−1
(Berthier et al. 2014). The
loss of ice thickness is also significant. At 1,900 m a.s.l.,
between 1994 and 2013, the Argentière glacier (MBM,
France) has lost 80 m of ice depth. On the Mer de Glace
(MBM, France), the rate of glacial thickness loss increased
from 1 m.a
−1
(1979–1994) to more than 4 m.a
−1
(2000–2008; Berthier and Vincent 2012). The Mer de
Glace loss in thickness was up to 60 m at the front
ARCTIC, ANTARCTIC, AND ALPINE RESEARCH 177

(1,500 m a.s.l.) during the period 1979–2003 (Berthier
2005). At the same time, glacier fronts retreated dramati-
cally: 366 m between 1994 and 2007 for the Mer de Glace,
with a particularly rapid period of shrinkage of 40 m/y
between 1998 and 2005 (Vincent 2010). Glacial shrinkage
affects high elevations (i.e., above the glacier equilibrium
line altitude—ELA—separating the accumulation and abla-
tion zones). Between the 1960s and 2008, the glacier surface
areas on the French side of the MBM decreased by 16% at
2,200–2,600 m, 11% at 2,600–3,000 m, 6% at
3,000–3,500 m, and 3% at 3,500–4,000 m a.s.l. (Deline
et al. 2012). For example, the surface of the Talèfre glacier
lowered by 5–10 m between 3,000 and 3,500 m a.s.l. over
the period 1979–2003 (Berthier 2005). At 3,613 m a.s.l., the
Géantglaciersurfaceloweredby20mbetween1992and
2012 (Ravanel et al. 2013).
Glacial shrinkage coincides with a rise of the ELA of
170 m between 1984 and 2010 in the western Alps
(Rabatel et al. 2013). Also, combined with a decrease
in winter snow accumulation, the snow cover on the
glacier surfaces tends to decrease both in area and
thickness. As a result, crevasses appear earlier in spring
and areas of bare ice increase in summer. The decrease
in snow cover on glaciers also results in an increase in
the number of open crevasses, while snow bridges may
be getting more fragile. The fragility of snow bridges is
probably increasing as the average altitude of the 0°C
isotherm has risen by 400 m since 1980 (Böhm et al.
2010) and the frost frequency has decreased (Pohl et al.
2019). The snow pack does not refreeze and consoli-
date, especially during the night. As such, snow bridges
are probably weakening earlier in spring and during
heat waves.
In some cases, glacier retreat leads to more frequent
serac fall from the hanging fronts of warm and cold-
based glaciers (Fischer et al. 2006). In the MBM, serac
Figure 1. Location of the Mont Blanc massif, the itineraries studied and their level of evolution.
178 J. MOUREY ET AL.

fall mainly occurs during the warmest periods of
the year and, on a secular scale, during or at the end
of the warmest periods (Deline et al. 2012).
Due to glacial shrinkage, paraglacial processes—
defined by Ballantyne (2002)as“the nonglacial earth-
surface processes, sediment accumulations, landforms,
landsystems and landscapes that are directly condi-
tioned by glaciation and deglaciation”—are intensify-
ing. A paraglacial period starts as a direct reaction to
deglaciation and ends when all glacial sediments have
been removed or stabilized (Church and Ryder 1972;
Ballantyne 2002). In this study, paraglacial processes
refer mainly to the erosion of moraines through rock-
fall and landslides (McColl 2012; Deline et al. 2015;
Draebing and Eichel 2018; Eichel, Draebing, and
Meyer 2018; Ravanel et al. 2018), illustrated by the
gullying of the inner flank of lateral moraines due to
very steep slopes, up to 80° (Lukas et al. 2012).
At the same time, permafrost—ground that remains
permanently at or below 0°C for at least two consecutive
years (Dobinski 2011)—tends to warm and degrade
(Haeberli and Gruber 2009). Even if all rockfalls cannot
be attributed to permafrost warming, as it is a natural
erosion process in high mountain environments (Allen,
Cox, and Owens 2011; Collins and Stock 2016;D’Amato
et al. 2016), its degradation results in more frequent and
voluminous slope instabilities (rockfalls, rock slides)
(Harris, Davies, and Etzelmüller 2001; Harris et al.
2009; Ravanel and Deline 2011; Ravanel et al. 2013;
Ravanel, Magnin, and Deline 2017). In the MBM, more
than 850 rockfalls (V > 100 m
3
) occurred between 2007
and 2018 (Ravanel and Deline 2015). Permafrost is con-
tinuously present above 3,000 m a.s.l., on average, on
north faces and above 3,600 m a.s.l. on south faces
(Magnin et al. 2015).
The change in the high mountain environment raises
the question of how mountaineering itineraries have been
affected and what effect this has had on their popularity.
The MBM: The 100 Finest Routes by G. Rébuffat
(1973), as reference sample
G. Rébuffat’sguidebook—The Mont Blanc Massif: The
100 Finest Routes—has for several decades been a major
source of information for mountaineers. It was the first
guidebook to offer a selection of routes based on their
quality, unlike guidebooks of the same period –such as
the Vallot series –that usually drew up the most
exhaustive list of all the routes of a region. This is
why it quickly became popular for any mountaineer
visiting the MBM. In addition, it arranges routes by
increasing difficulty (from facile [easy] to extrêmement
difficile [extremely difficult]) and/or commitment (the
potential seriousness of a fall), and so can be used as
a reference for progression. All types of routes are
covered—rock, snow, ice and mixed (snow/ice and
rock)—and they have been chosen from throughout
the massif (Figure 1), making it a relevant and repre-
sentative selection of all mountaineering itineraries in
the MBM. For each itinerary, an introductory text
describes the itinerary, the first ascent, the elevation
gains, the level of technical difficulty, the time required,
the necessary equipment, the starting point and the
route to follow.
Not all the itineraries presented by G. Rébuffat were
taken into consideration in this study: itineraries 1 and
3–8 were ruled out because they are located outside the
MBM (in the Aiguilles Rouges massif, Valais Alps and
Aosta Valley). On the other hand, several itineraries are
presented together in the guidebook, as they can by
climbed the same day or on the same trip into the
mountains; but these have been treated separately in
this study. Itinerary 17 is an example: Rébuffat recom-
mends combining the normal route on Mont Blanc du
Tacul (4,248 m a.s.l.) with the Cosmiques ridge on the
Aiguille du Midi (3,842 m a.s.l.) in a single day.
Altogether, 95 itineraries were analyzed. In some
cases, several descents are possible; only the most clas-
sic were chosen.
Methodology
Our study is structured according to two main data col-
lection methodologies. First, semi-structured interviews
were carried out with alpine guides, including instructors
at the National School of Skiing and Mountaineering
(ENSA), hut keepers, employees incharge of the manage-
ment of the trails, first ascensionists and guidebook edi-
tors. In total, 31 people were interviewed. These people all
have a good knowledge of mountaineering itineraries and
19 of them have been active in the MBM since the 1980s,
but only four senior alpine guides who have frequented
the range since the 1970s were interviewed. The two main
questions were: (1) What are the ongoing long-term
changes on the itineraries (since the 1970s)? and (2)
How have these itineraries changed with regards to tech-
nical difficulty, objective dangers, and optimal periods for
making an ascent? The interviewees were only asked to
report long-term changes of the itineraries. Attribution of
the climate-related changes was carried out by two
researchers, both very familiar with the MBM, and their
results were compared afterwards. In some cases, to con-
firm the information collected during the interviews, the
descriptions of itineraries from Rébuffat’s guidebook were
compared with those from recent guidebooks (Damilano
ARCTIC, ANTARCTIC, AND ALPINE RESEARCH 179

2005,2006; Piola 2006; Laroche and Lelong 2010;Batoux
2012;Pusch,Dumler,andBurkhardt2014).
Two sets of interviews were conducted in fall 2017. The
first set led to the identification of the climate-related
changes that have affected the itineraries (Table 1). Some
of these have been the subject of scientific research, which
has enabled us to confirm their existence and describe them
more accurately. A second set of interviews was conducted
in order to list the geomorphic and cryospheric changes
affecting each of the 95 itineraries studied. At least 10
itineraries were considered per interview, which thus
tended to be relatively long (up to 2–3hours).Thestudied
itineraries varied from one interview to another, depending
on the memories of the interviewees. In the end, each of the
95 itineraries was studied during at least two different inter-
views. The database was formalized as a table, cross-
referencing each of the 95 itineraries with the 25 geo-
morphic and cryospheric changes. This was completed
during the interviews. The results are presented in Table
1. However, one of the limits of this method of data for-
malization is that the location and the intensity/character-
istics of each of the changes identified were not recorded.
Each itinerary was divided into three parts: (i) the approach,
which begins in the valley or at the top of a cable car and
ends either at the foot of the rock wall to be climbed or at
the bergschrund; (ii) the route and its continuation to the
summit; and (iii) the descent, which begins at the summit
and ends in the valley or at the top of a lift.
During this second set of interviews, a 5-level scale
was developed to evaluate the evolution of the climbing
parameters of each itinerary. The climbing parameters
considered are: itinerary type (ice, snow, mixed or
Table 1. Climate-related geomorphic and cryospheric changes affecting mountaineering itineraries and their climbing parameters.
180 J. MOUREY ET AL.

rock), technical difficulty, level of exposure to objective
dangers, and any changes to the optimal period for
making an ascent (i.e., when the number/intensity of
the changes affecting it are the lowest).
●Level 0. The itinerary and the parameters deter-
mining the way it is climbed have not changed.
●Level 1. The itinerary and its climbing parameters
have slightly evolved. Only a short section of the
itinerary is affected by geomorphic and cryo-
spheric changes, and this does not result in
a significant increase in objective dangers and/or
in technical difficulty.
●Level 2. The itinerary and its climbing parameters
have moderately evolved. The optimal periods for
making an ascent have become rare/unpredictable
in summer and shifted toward spring and some-
times fall. Objective dangers and technical diffi-
culty are increasing and mountaineers therefore
have to adapt their technique.
●Level 3. The itinerary and its climbing parameters
have greatly evolved. Generally, the itinerary can
no longer be climbed in summer. Objective dan-
gers and technical difficulty have greatly increased
due to the number and intensity of the geo-
morphic changes affecting it. Mountaineers have
had to fundamentally change the manner in which
they climb the itinerary.
●Level 4. The itinerary has completely disappeared.
The itinerary can no longer be climbed.
The identification of the changes affecting
a mountaineering itinerary varied greatly from one
person to another depending on the climbing cir-
cumstances encountered during the ascent (i.e., the
occurrence/absence and the intensity of the changes
previously identified), the technical level and num-
ber of their clients and their personal perception.
The changes identified were not always the same,
nor assessed to the same degree. As an example, at
the end of the summer season when the glacier
surface is icy, any increase in steepness is more
significant and easier to identify compared to the
beginning of the season when the glacier surface is
still covered with snow. Moreover, the interviewees
tended to underestimate the number of changes
affecting an itinerary. Indeed, it seems that indivi-
duals usually notice only the changes that are rele-
vant when they are making an ascent, without
necessarily taking into account the season and high
mountain climate-related evolution. It was the inter-
viewers’role to encourage interviewees to identify
only long-term changes rather than focusing on
their last ascent. For this reason, a great number
of interviews were conducted in order to validate
the data collected.
Results
Geomorphic and cryospheric changes affecting
mountaineering itineraries and the manner in
which they are climbed
Twenty-five geomorphic and cryospheric changes were
identified (Table 1). These result from glacial shrinkage,
a reduction of ice-snow cover, changes in the structure
of snow ridges, and permafrost warming. For each
geomorphic change, its impact on the climbing para-
meters was identified (Table 1): increase in objective
dangers, technical difficulty and commitment, length-
ening of the itinerary and any increase in the effort
required to climb it.
All the types of changes that have affected each route
between the 1970s and today were listed. On average,
an itinerary has been affected by nine geomorphic
changes. The appearance of bedrock (85 itineraries
affected), wider crevasses and bergschrunds (78) and
steeper glaciers (73) are the three most commonly
observed changes. They cause an increase in danger-
ousness and technical difficulty. The alpine guides
interviewed all had to deal with thinner and weaker
snow bridges, while crevasses that were never or rarely
observed, now appear more often.
Finally, regarding the evolution scale used to eval-
uate changes to the itineraries studied from
a mountaineering point of view (Figure 1), 2 had
not evolved (level 0), 30 had slightly evolved (level
1), 34 had moderately evolved (level 2), 26 had
greatly evolved (level 3), and three had disappeared
(level 4). Four examples are described below to better
illustrate those evolutions and the implications for
mountaineering. Moreover, there is a direct correla-
tion between the number of geomorphic changes
affecting an itinerary and its level of evolution. On
average, for level 1, 7.4 changes were affecting the
itineraries, 10 for level 2, 11.5 for level 3 and 12.5 for
level 4. It is also important to note that during the
summer of 2018, the evolution levels of three itiner-
aries changed: from 1 to 3 (Cosmiques ridge—itiner-
ary 17), 1 to 4 (Lépiney route—itinerary 37) and 1 to
2 (Rébuffat-Bacquet route—itinerary 55). The geo-
morphic changes responsible for those three evolu-
tions have been identified thanks to a network of
observers (mainly alpine guides and hut keepers)
developed to study geomorphic changes in the
MBM (Ravanel and Deline 2013).
ARCTIC, ANTARCTIC, AND ALPINE RESEARCH 181

Different patterns of evolution depending on the
nature of the routes (rock, snow, ice or mixed)
●Disappearance of rock route because of massive
rockfall: the example of the Petit Dru (3,733 m
a.s.l) west face
The Bonatti route on the Petit Dru west face (itin-
erary 92) was an emblematic rock climb first ascended
in 1955 by the well-known Italian mountaineer Walter
Bonatti. However, most of the route disappeared after
a 700 m-high pillar collapsed in 2005 (Figure 2; Ravanel
and Deline 2008). This route has a level 4 evolution.
●Snow and mixed route which can no longer be
climbed in summer because of ice/snow cover
melting early: the example of the Whymper
couloir on the Aiguille Verte (4,122 m a.s.l.)
The Whymper couloir (itinerary 41) is the original
route used by Edward Whymper for the first ascent of
the Aiguille Verte (4,122 m a.s.l.) in 1865. It is still
a classic and emblematic route.
In 1973, Rébuffat classified this itinerary as a snow climb.
Today, the ice/snow cover necessary for an ascent of the
couloir has been very significantly reduced (Figure 3).
Indeed, it completely melts out early in summer and frac-
tured bedrock appears. This creates circumstances where
rock fall is frequent. In addition, the bergschrund at the
bottom of the couloir becomes very wide and difficult to
cross. Rockfall is observed frequently (oral communication,
C. Lelièvre, keeper of the Couvercle hut) and a 22,000 m
3
rockfall occurred on the right bank of the couloir in
August 2015 (Ravanel, Magnin, and Deline 2017;
Figure 3). These environmental changes have led to an
increase in the technical difficulty and inherent danger of
the route and it is now possible to climb it only very early in
summer. The level of evolution applied to this itinerary is 3.
●Rock routes whose approach has been affected: the
examples of the Aiguille du Midi (3,842 m a.s.l.)
southfaceandtheAiguilleduMoine(3,412ma.s.l.)
east face
The Rébuffat-Bacquet route (itinerary 55), climbed
in 1956 on the south face of the Aiguille du Midi, is
a classic rock climb that sees a lot of traffic in summer.
Apart from a small rockfall, it has not yet been directly
affected by climate change, but the approach to the
original starting-point of the route has become more
difficult because of two main factors. First, the east
ridge of the Aiguille du Midi that leads to the bottom
of the face is becoming narrower. It is orientated west–
east, meaning that melting is much more important on
its south side than on its north side. This makes it
steeper, and it tends to become icy earlier in summer.
Crevasses also now appear. Secondly, because the Géant
glacier at the foot of the face has lost over 25 m in
depth over the past 30 years, the route’s historic start-
ing-point is now difficult to reach (Figure 4). Climbers
now have to follow the start of the Contamine route,
which is technically more difficult (graded F6b instead
of F6a; see Hagenmuller, Marsigny, and Pallandre
2016) than any other pitches on the Rébuffat-Bacquet
route. These environmental changes have led to an
increase in the technical difficulty and commitment
needed to reach the start of the route. The level of
evolution applied to this itinerary is 2. Because the
surface of the Géant glacier lowered greatly during the
2018 heat wave, the route was not accessible at the end
of the summer period. A very difficult climbing section
has appeared.
This situation is identical for the majority of rock
routes but the increase in difficulty varies depending on
Figure 2. The Petit Dru West face, October 2017. A major part
of the route has disappeared because of a rock collapse in 2005
and a further rockfall in 2011 (292,000 m
3
).
182 J. MOUREY ET AL.

the extent of the ice thickness loss and the nature of the
terrain exposed. In some cases, the route may lose its
intrinsic logic and aesthetics if sections of climbing
appear which are much more difficult than the rest of
the route. This is the case for the Labrunie-Contamine
route (itinerary 51) on the Aiguille du Moine (3,412 m
a.s.l.) east face. A 15 m-high section of F6c climbing is
now exposed at the start of the route because of the
lowered surface of the Talèfre glacier. The rest of the
route is graded F6a maximum. This short, difficult
section has made the route less attractive, and it is
now climbed less frequently than before. The level of
evolution applied to this itinerary is 2.
●Rock route whose descent is more difficult and
dangerous because of glacial shrinkage: the
example of the Aiguille de l’M (2,844 m a.s.l.).
TheAiguilledel’M north ridge (itinerary 18) is
a very popular rock route. The approach and the
route are not affected by geomorphic or cryospheric
changes, notably because of its relatively low altitude.
However, the way down follows a south-facing couloir
to reach the Nantillon Glacier, at 2,500 m a.s.l.
Because of the lowering of the glacier surface, the
couloir is becoming steeper and very exposed to rock-
fall coming from the lateral moraine of the glacier. In
order to reduce the danger and the technical difficulty,
abseils and ladders have been installed in the couloir.
Therefore, the itinerary can be climbed all summer
and the descent is now less technically difficult. The
level of evolution applied to this itinerary is 1.
Discussion
The degree and type of evolution to an itinerary
depends on the nature of the terrain
In general, snow, ice and mixed itineraries have been
more affected by climate change, with a 2.4 average
level of evolution, than rock routes with a 1.6 average
level of evolution. This finding is confirmed by
a Correspondence Factor Analysis (CFA; Volle 1997)
linking the level of evolution of the itineraries with
their type (rocky, snow, ice and mixed), difficulty, and
orientation (Figure 5). Itineraries undergoing level 3
evolution are mainly mixed and snow routes (46.2%
and 26.9%, respectively) graded “assez difficile”(quite
difficult) or “peu difficile”(not very difficult) and facing
north-east. On the other hand, rock routes are statisti-
cally underrepresented (11.5%) in this level of evolu-
tion. The routes undergoing level 0, 1 and 2 evolutions
are mostly rock routes (100%, 82.8% and 54.3%, respec-
tively) for the highest level of difficulty (extrêmement
difficile [extremely difficult] and très difficile [very dif-
ficult]). Variable aspects are represented. In the 0 level
of evolution, ice routes are statistically underrepre-
sented (0%). We can conclude that rock routes are
less affected by the effects of climate change than
snow, ice and mixed routes.
Not all the geomorphic changes identified in this
work affect the itineraries in the same way. The
approaches are mainly affected by wider crevasses and
bergschrunds (53/95), paraglacial processes (41/95) and
the appearance of new crevassed areas (27/95). The
changes mainly affecting the routes are the appearance
Figure 3. The Whymper couloir on the Aiguille Verte (4,122 m a.s.l.) south face. The route is marked in red. A: situation at the end of the
1960s (picture from the guidebook). B: situation at the end of August 2017 (photo C. Lelièvre). The ice/snow cover in the couloir has
undergone a very significant reduction, which has exposed fractured bedrock, leading to frequent rockfalls (orange arrows). The orange
star indicates the point where a 22,000 m
3
rockfall released in 2015. The red triangles indicate similar features.
ARCTIC, ANTARCTIC, AND ALPINE RESEARCH 183

of smooth slabs or unstable bedrock (77/95) and all
changes related to the disappearance of ice/snow
cover and the evolution of snow ridges (52/95).
Finally, the changes predominantly affecting the des-
cents are a steepening of glaciated slopes (63/95), wider
crevasses and bergschrunds (59/95), and paraglacial
processes (41/95). There is also a correlation between
some changes and the orientation of the routes. For 39
routes located on southern slopes, 23 are affected by
processes due to permafrost degradation and 22 by the
appearance of smooth slabs or fractured bedrock. On
the other hand, changes in serac fall and the appearance
of bare ice mainly affect north-facing routes. Other
changes, such as the reduction in ice/snow cover,
equally affect routes on southern and northern aspects.
Changes in the optimal season for making an
ascent as a result of increased levels of difficulty,
commitment and objective danger
It is difficult to measure the effects of one or several
changes on the climbing parameters of an itinerary. In
general, the identified changes imply an increase in
technical difficulty, dangerousness and commitment
of these itineraries in summer, but seasonality must
be addressed.
The evolution of mountaineering itineraries is con-
ditioned on two different time scales. The main time
scale addressed in this study is climate related and
covers the period from the 1970s to 2018. However,
deterioration on mountaineering itineraries’climbing
parameters can be reduced or increased by seasonal
factors. Changes are usually less impactful at the begin-
ning of the summer season, when the winter snow pack
has not yet completely melted out (even though snow
pack in general is decreasing both in quantity and
duration), and they increase at the end of the summer
season or during heat waves (which are becoming more
and more frequent and intense due to climate change)
(IPCC [Field C.B., Barros V.R., Dokken D.J., Mach K.J.,
Mastrandrea M.D., Bilir T.E., Chatterjee M., Ebi K.L.,
Estrada Y.O., Genova R.C., et al.] 2014). Therefore,
itineraries when in an optimal period for making an
ascent—more and more commonly outside the summer
period—are not necessarily any more difficult or dan-
gerous than before. It is for this reason that good and
stable periods for mountaineering tend to be more
variable in summer and shift toward spring, fall (as
temperatures start to drop and new snow falls occur)
and even winter, especially for snow, ice and mixed
routes. Depending on the nature of the itinerary,
much more attention must be paid to the evolution of
climbing parameters. According to the interviewees, the
summer mountaineering season has shifted by
three weeks toward spring compared with the 1980s.
This finding confirms the work of Bourdeau (2014)
conducted in the Écrins massif.
An itinerary greatly affected by the effects of
climate change effects may still be very popular
There is not necessarily a direct link between the level
of change of an itinerary and its popularity. A notable
example is the “normal”(classic) itinerary to the
Figure 4. Aiguille du Midi south face, September 2018. The
original start to the Rébuffat-Bacquet route (1956) is no longer
accessible directly. The lower part of another route must be
climbed to join it.
184 J. MOUREY ET AL.

summit of Mont Blanc (itinerary 24). It has been
greatly affected by climate change, with an increase in
technical difficulty and especially in dangerousness.
Rockfall is increasingly frequent in the Grand Couloir
du Goûter and causes a significant number of accidents.
Between 1990 and 2017, there were an average of 3.7
deaths and 8.5 injuries per summer on the crossing of
the couloir and the climb to the Goûter ridge, mainly
due to human error and rockfall (Mourey et al. 2018).
In addition, large crevasses which are difficult to cross
are appearing even at high altitude (above 4,000 m a.s.
l.), while the summit ridge is becoming narrower. The
descent described by Rébuffat is no longer used in
summer, as it has become too crevassed. Even though
the level of evolution applied to this itinerary is 3, it is
still one of the busiest mountaineering itineraries in the
world because of the prestige of climbing the highest
summit in the Alps.
On the other hand, some itineraries that have only
been slightly affected by climate change are much less
popular than in the past. To explain this, other socio-
economic factors and the evolution of mountaineering
itself must be considered. Today, mountaineers tend to
limit their risk-taking and their exposure to objective
dangers such as rock and serac fall. Other itineraries are
no longer popular because the approach is long and/or
the in situ equipment is old (Bourdeau 2003). As an
example, according to the alpine guides interviewed,
the north face of the Aiguille de Bionnassay (4,052 m
a.s.l.—itinerary 49) was a classic ascent during the
1980s. Today, it is no longer climbed in summer
despite a relatively low level of evolution (2) because
of the danger of serac fall. This danger was also present
40 years ago.
In some cases, the evolution of mountaineering itiner-
aries due to the effects of climate change leads to them
becoming less popular. This is the case for the traverse of
the Dômes de Miage (3,673 m a.s.l. –itinerary 13), a very
famous and beautiful snow climb. During the summer of
2015, a crevasse opened on the summit ridge, which itself
had become narrower and icier. In addition, a rockfall
occurred on the route, making it more technicallydifficult
and exposing it to further rockfall. The ridgeline was no
longer being traversed, with climbers choosing to descend
by the ascent route. This made the itinerary less aestheti-
cally pleasing and the number of people staying at the
Figure 5. Cross-tabulation and graphical representation (CFA type) of the relationships between the level of evolution of a route for
mountaineering purposes and its nature (rock, snow, ice and mixed), difficulty and aspect. The closer the circles are, the more
meaningful their relations are. The statistically strongest relationships are underlined.
ARCTIC, ANTARCTIC, AND ALPINE RESEARCH 185

Conscrits hut (2,602 m a.s.l.), which gives access to the
route, fell by 25% that summer. This situation occurred
again in 2016 and 2017, with significant economic con-
sequences for the hut keeper. The Couvercle hut (2,679 m
a.s.l.) is facing the same situation, with climbing para-
meters on most routes deteriorating earlier in the summer
season. According to the former two hut keepers, the
steady decline in the number of overnight stays (35%
over the last 15 years) has been accentuated by the evolu-
tion of the mountain itineraries, perhaps concurrently
with socio-economic factors.
Is the aesthetic quality of high mountain areas
deteriorating?
Climate change–related geomorphic and cryospheric
changes result in significant changes to the landscape
(Moreau 2010). The general drying of high mountain
environments leads to the appearance of more and more
rocky terrain while glacial surfaces are decreasing. As
snow cover on glacier surfaces melts out faster and at
higher altitudes, bare ice is appearing, and supraglacial
debris cover is increasing (Deline 2005; Martin 2011)
while rock falls form more continuous deposits. All the
interviews carried out indicate that high mountain land-
scapes no longer conform to the classic representation of
blue ice and “eternal snow”(Moreau 2010; Bourdeau
et al., 2014). The motivation of some mountaineers to
go into the high mountains is thus reduced. “I note that
there is less interest to go on glaciers […] that are dirty,
with a dull color; they are less attractive in a certain way”
(oral comm. B. Pelissier, alpine guide, Oct. 2017).
Limits
Because Rébuffat’sguidebook dates from the 1970s, it
does not present any steep, narrow ice climbs. These
“concealed and narrow ice couloirs”(Jouty and Odier
1999) are seasonal (Faup 2003) and were largely devel-
oped in later years thanks to improvements in moun-
taineering equipment. According to the alpine guides
interviewed, the formation of ice gullies is becoming
increasingly less frequent and often the quality of the
ice is lower. During the 2016 and 2017 winters, almost
no such ice gullies formed in the MBM. It seems that
the main factors explaining the disappearance of these
routes are the lack of winter and spring snowfall and
the more rapid melting of the ice/snow cover. This
phenomenon seems to be very recent and due, to
a large extent, to an increase in the frequency of winter
warm spells since the beginning of the 2000s.
Another factor limiting our methodology must also
be highlighted. Because some itineraries have the same
approach and/or descent, some changes have been
overrepresented. This is particularly the case for para-
glacial processes that affect all the approaches and
descents in the Mer de Glace basin (Mourey and
Ravanel 2017). One way of limiting this bias would
have been to consider only the routes themselves, and
not the approaches and the descents; but this method
would not have given an accurate representation of the
difficulties that mountaineers are facing throughout the
whole itinerary.
Moreover, it is not possible to objectively compare the
grade of the itineraries between the 1970s and today, as
the grading system (Cox and Fulsaas 2006), equipment
and technical level have changed considerably.
Finally, because rock slope instabilities resulting
from post-glacial decompression (Ballantyne 2002) are
relatively uncommon in the MBM (Deline et al. 2012)
and difficult to differentiate from the many rockfalls
resulting from permafrost degradation, they have not
been considered in this study.
Conclusion
The effects of climate change on high mountain envir-
onments has led to changes to mountaineering itiner-
aries and their climbing parameters. In addition to
previous studies, this one presents an exhaustive list
of the 25 geomorphic and cryospheric changes related
to climate change that can affect a mountaineering
itinerary. On average, an itinerary in the MBM is
affected by nine of these changes. Moreover, the
impacts of each of these changes have been documen-
ted and quantified for the first time. The exposure of
bedrock, widening of crevasses and bergschrunds and
steepening of glaciated slopes are the main changes.
The impact of these changes on mountaineering has
been quantified for 95 itineraries. Only two routes have
not evolved, 30 have slightly evolved, 34 moderately
evolved, 26 strongly evolved and three have disappeared.
As a result, mountaineering itineraries tend to be more
technically difficult and more dangerous. Optimal periods
during the summer months have become rarer and more
unpredictable. This result in the progressive reduction in
the terrain available for mountaineers as the summer sea-
son progresses and good periods are now more likely to
occurinspring,fallandevenwinteronsomeitineraries.
The evolution of a mountaineering itinerary due to the
effects of climate change may lead to an important decrease
in its popularity, but socio-economic factors (changes in
techniques, customers, etc.) must also be considered.
Climate change is expected to accelerate during the
coming decades (IPCC [Field C.B., Barros V.R., Dokken
D.J., Mach K.J., Mastrandrea M.D., Bilir T.E.,
186 J. MOUREY ET AL.

Chatterjee M., Ebi K.L., Estrada Y.O., Genova R.C., et al.]
2014), and this would lead to ever-increasing changes to
the highly sensitive high mountain environment. Changes
to mountaineering itineraries as attested to in this article
are expected to continue and increase. This perspective
may have significant consequences for mountaineering
and the ability of high mountain professionals, such as
alpine guides and hut keepers, to adapt.
Acknowledgments
The authors thank the personnel of the ENSA library for
making the library and all its resources available to us and
Neil Brodie, professor at ENSA, for the English language
editing. This study was funded by the EU ALOCTRA project
AdaPT Mont Blanc. Finally, we gratefully thank the anon-
ymous reviewers and the editor for their constructive com-
ments on the manuscript.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Jacques Mourey http://orcid.org/0000-0002-3717-8553
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