How will the Alps respond to climate change?
Scenarios for the future of Alpine waters
Lučka Kajfež-BogatajUniversity of LjubljanaIPCC WG2 Vice chair
Outline
•
Mountains as water towers•
Observed changes
•
Climate models and scenarios•
Future of Alpine water balance
predictions of impacts, extremes, snow reliability, abrupt changes
•
Conclusions
Climate change: vulnerable
regions
in Europe
Coastal regions
Mountain regions
Rivers
IPC
C, 2
001
Baumgartner et al., Baumgartner et al., 20042004
•• PrecipPrecipitationitation
doublesdoubles•• ET: little changeET: little change•• Runoff: 4x greaterRunoff: 4x greater
Global temperature and temperature in Alps Säntis -
Switzerland (2490 m) and Sonnblick -
Austria (3106 m) last century's
warming exceeded 1.5 °C, which is more than twice the global average warming
-1.5
-1
-0.5
0
0.5
1
1.5
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
GlobalAlps
ΔT
from
1961
-199
0 [°
C]
Observed climate change in Alps
Observed climate change in Alps
•
Precipitation: -
Annual prec. slightly rising in French Alps
-
Regional trend differences (particularly between NW and SE part of Alps: 10 % increase in the NW and 10 % decrease in the SE )
-
Some long-term trends have abruptly changed into their opposites (SE part of the Alps: winter prec. decreasing since 1980, autumn prec. increasing since 1990)
•
Snow: -
Snow parameters in the Alps are characterized by a marked declining gradient (the duration of continuous snow cover is clearyl declining at all elevations and it melts much earlier)
-
Shrinkage of mountain glaciers (glaciers have lost one third of their area and one half of their mass from 1850 to 1990)
•
Sunshine duration: -
Annual sunshine shows clear trend of “brightening” at higher elevations (above 2000 meters), elevations below 1000 meters show weaker to
not significant trend
Climate Models and Climate Scenarios Climate models
and other types of models are used
for future estimates.
•
Depict physics, chemistry and biology of the environment in form of mathematical equations, solved by a computer program.
•
Require large amounts of input data (emissions, topography, historical climate data).
• Have uncertainties.
Results of climate model: projections of the response of the climate system to future emissions scenarios
A1
B1
A2
B2
Economic
Environmental
Global Regional
Population
Econ
omy
Tech
nolo
gy Energy
(Land-use)
Agriculture
D r i v i n g F o r c e s
The SRES driving forces and storylines
Nakicenovic et al. (2000)
Figures are based on IPCC SRES scenario A2. The projected climate impacts are estimated for 2071-2100 relative to 1961-1990. The maps are based on DMI/PRUDENCE data (http://prudence.dmi.dk)
•
Changes in temperature (affect snow-cover, snow pack and biodiversity)
•
Changes in precipitation patterns, particularly extreme weather events (droughts and floods)
•
Changes in the wind regimes (the foëhn effect associated in leeward sides can affect the snow and vegetation distribution and human health).
•
Land-use changes and conflicts (arise from urbanisation and competition between different sectors).
•
Increase in air and noise pollution on transit routes, major roads and in cities affect human health.
THE ALPS: Key environmental pressures
•
Changes
in water balance •
Increasing
vulnerability of settlements and
infrastructure to natural hazards •
Changes
in biodiversity and stability of
ecosystems •
Increasing risks
of economic losses in winter
tourism and summer tourism due to heat waves
THE ALPS: Key vulnerability issues
DJF MAM JJA SON0123456789
Min Ensemble Max
ALPS: Change in seasonal mean 2-m temperatureby the end of this century
•
Increased temperature variability in summer (inter-
annual and daily time scales)
•
Decreased temperature variability in winter
Consequences for water balance•
Enhanced hydrological cycle in Alps: higher rates of evaporation, greater proportion of liquid to solid prec. (soil moisture, groundwater reserves, frequency of droughts and floods)
•
The duration of snow cover is expected to decrease by several weeks for each °C of temperature increase
•
An upward shift of the glacier equilibrium line is expected from 60 to 140 m/°C
•
Small glaciers will disappear, while larger glaciers will suffer a volume reduction between 30% and 70% by 2050
Changes in seasonal
precipitation in the Alps
(HIRHAM RCM)
250
500
Winter Spring Summer Autumn
1961-1990Se
ason
alpr
ecip
itatio
n [m
m]
450
400
350
300
2071-2100 (A2)
2071-2100 (B2)
Beniston, G
RL, 2006
Annual: 1605 mmAnnual: 1591 mmAnnual: 1597 mm
0
10
60
Winter Spring Summer Autumn
Num
ber o
f eve
nts
beyo
nd 9
9% p
erce
ntile
Changes in extreme precipitation in the Alps
(HIRHAM RCM)
1961-1990
2071-2100 (A2)
2071-2100 (B2)
Beniston, G
RL, 2006
40
20
30
50
70108 events
127 events
141 events
SNOW AND PERMAFROST
•
Snow is one of the substances which reacts the most quickly and visibly to ambient temperature.
•
More than any other substance it shows what global warming really means
•
For every °C increase in T snowline will on average rise by 150 m (at lower elevations by more than this average)
•
A2 scenario: As a consequence to 4°C shift in mean winter T. snow duration is likely to be reduced by 50 % at altitudes 2000 m to 95 % at levels below 1000 m.
•
The lower elevation of permafrost is likely to rise by several hundred meters (destabilisation of mountain walls and increase in the frequency of rock falls)
Elevation of snow reliability (m a.s.l.)Alptal Hirschbichl Dischma
Saltina Verzasca
1200
1600
2000
2400
1970 2000 2030 20601200
1600
2000
2400
1970 2000 2030 2060yearyear year
yearyear
Elevation moves up ca. 150 m/ 1°C warming.
A1FI
A2
B1
B2
A2_CGCM2
A2_CSIRO2
A2_PCM2
Zierl et al. 2004 (in prep).
1200
1600
2000
2400
1970 2000 2030 2060
1200
1600
2000
2400
1970 2000 2030 2060
1200
1600
2000
2400
1970 2000 2030 2060
Snow volume in Alps (as a function of altitude)
500
1000
1500
2000
2500
3000
3500
4000
4500
0 10 20 30 40 50 60
Total volume [109 m3 ]
Alti
tude
[m]
Today’s climate, humid winters
Today’s climate, dry winters
+4°C, humid
+4°C,
dry
Consequences for floods: the buffering
effects of snow
Runoff
Floodlevel
Shifts in seasonality of
runoff
in central Alps (HIRHAM RCM)
Mea
n 30
-yr r
unof
f [m
m/d
ay]
0
1
2
3
4
5
6
1 31 61 91 121 151 181 211 241 271 301 331 361Julian Day
Winter Spring Summer Autumn
1961-1990
2071-2100
Reducedsnow melt
Reducedglacier melt
+90% -5% -45% -20%
Enhancedflood risk
Enhanceddrought risk
Alpine runoff regimes
month
0
100
200
300
400
1 2 3 4 5 6 7 8 9 10 11 12
currentA1FI HadCM3A2 HadCM3B1 HadCM3B2 HadCM3A2 CGCM2A2 CSIRO2A2 PCM2
Zierl et al. 2004 (in prep).
Example Dischma valley, 2051 - 2080m
m
Observed changes in seasonality of dischargeRiver Savinja in Slovenia
month1991-20001961-90
Mean change in winter potential water availability (mm) over the Mediterranean region for the A2 emissions scenario for 2071-2100 compared with 1961-1990
Mean change in summer potential water availability over the Mediterranean region for the A2 emissions scenario for 2071-2100 compared with 1961-1990
CONCLUSIONS•
The Alps are particularly vulnerable to climate change and already suffering from higher increases in temperature than the European average.
•
Climate change is already affecting discharge of alpine rivers and is increasing natural hazards.
•
It leads to economic losses in winter tourism especially in areas at lower altitudes.
•
These trends are projected to be exacerbated under enhanced climate change.
CONCLUSIONS•
The water regime in alpine
high mountains will
undergo
fundamental change. •
Because the Alps are the primary source for such major rivers as the Rhine, Danube, Rhone, … the impact of reduced mountain precipitation would be felt far beyond mountainous regions themselves
•
The average flow of alpine rivers will
increase in winter and significantly decrease in summer
–
reduction in
water availability for industry, agriculutre and domestic use
•
Flash floods would probably increase significantly•
Drastic
change in climate could significantly increase the
existing danger of mudflows
CONCLUSIONS•
By 2030
from 20 to
75% of today's glaciers (30 to 70% in
terms of area) will disappear
(by
2100 from 60 to
95% and 45 to 90% in terms of area)
•
The guaranteed snowfall altitude would rise from 1300 to about 1300 to 1600
m by 2030.
Elevation of a reliable
snow cover will rise between 200 and 400 m from about 1300 m today to 1500 m to 1700 m at the end of the 21st century.
•
Retreat and upward shift of the permafrost will cause-
a widespread reduction in stability of formerly
glacierized or perennially frozen slopes. -
increased risk of land-slides and sediment loads in
rivers and lakes -
destabilisation of infrastructure in high altitudes
-
increased need for additional avalanche barriers and flood protection facilities
Thank you for your attention