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