GLOBAL WARMING AND THE GREENHOUSE EFFECT

Our planet temperature is warming significantly dueto human activities?

OR

Last few years warming is part of a natural global cycle?

1998 : The warmest year on record (1850-2005)The warmest year of past thousand, based on tree rings

GLOBAL WARMING CONTROVERSY

Scientific strong consensus:

• Global surface temperatures have increased in recent decades• Trend is caused mainly by human-induced emissions of greenhouse gases.

No scientific body disagrees with this view

GREENHOUSE EFFECT

The atmosphere traps longwave radiation and returns it to the surface

Greenhouse gases (LWR absorbers):CO2, water vapor

Greenhouse liquid:Clouds (tiny water droplets)

IPCC: INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE

Role: To assess the latest scientific, technical and socioeconomic literature produced worldwide for understanding the risk of human-induced climate change, its impacts and options for adaptation and mitigation

It’s a scientific intergovernmental body set up by the WMO (World Meteorological Organization) and by the UNEP (United Nations Environment Program)

http://www.ipcc.ch/

•During last decade, mass balance in the tropical Andes glaciers shows a strongly negative trend.

•Fluctuations in mass balance, measured prior 1983 on several glaciers of the Cordillera Blanca (Northern Peruvian Andes) indicate that the acceleration in the glacier retreat had already begun after 1976/77

GLOBAL WARMING AND GLACIER SHRINKAGE

Glaciers monitored by IRD and South Americaninstitutions (Francou et al, 2005)

Mass balance:Difference between accumulation and ablation (melting and sublimation)

A glacier with:

Sustained (-) mass balance: will retreatSustained (+) mass balance: will advance

GLACIER SHRINKAGE

•The coherent way glaciers have been retreating, suggests a common response to a global climate forcing along the mountain chain

GLACIER SHRINKAGE

• According to general circulation models, temperatures will rise more in high mountains than at lower elevations. Max temperature increases are predicted to occur in high mountains of Ecuador, Peru, Bolivia and northern Chile (Raymond et al, 2006). This could have important consequences for mountain glaciers and for communities that rely on glacier-fed water supplies.

Projected changes in air temperature between 1990-99 and 2090-2099along a transect from Alaska to Southern Chile (scenarios using CO2 levels)Traingles show highest mountains at each latitude)(Raymond et al, 2006)

y = 0.02x + 18.68

10

12

14

16

18

20

22

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02

Central (3300 m)

y = 0.05x + 15.73

10

12

14

16

18

20

22

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02

Southern (3800 m)

y = 0.03x + 13.58

10

12

14

16

18

20

22

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02

Southern (4200 m)

Ticlio (Lima-Huancayo)(highest road point 4818 meters, 15807 feet)

Mount Pinatubo eruption (Philliphines, 1991)

AEROSOLS: COOLING EFFECT

MOUNT PINATUBO ERUPTION (Phillipines)

The volcanic eruption (June 1991) that cooled the planet

The second largest volcanic eruption of the 20th century

Volcanic activity Particles and gases (SO2)into stratosphere (aerosols)

Strong winds spread throughout the entirely layer

Aerosols reflect income radiation (cooling effect)

Aerosols : suspension of fine solid or liquid particles (smoke from fires, volcanic activity, air pollution)

GLOBAL DIMMING

The gradual reduction in the amount of global sun radiation at Earth’s surface

Gerald Stanhill (Israel):

Solar Radiation observations: 22% decrease (1950s-1980s)

Beate Liepert (Germany):Similar pattern in Alps

1950-1990 decrease of solar energy:• 9% Antartica•10% USA•30% Rusia

Antartic

Arctic

SEPTEMBER 12, 2001 (USA):

Near-total shutdown of air traffic during the three days

US climate absent from the effect of contrails (visible trails of condensed water vapor).

During this period, an increase in temperature range over 1°Cwas observed in some parts of the U.S.

EFFECTS OF GLOBAL DIMMING

• Masking effects of global warming

•Less solar radiation Less energy to produce evaporation

•Less evaporation Less precipitation (Droughts)

If we focus only in aerosol forcing: acceleration of greenhouse effects If we focus only in greenhouse gases: increase of droughtsIt’s important to handle the two problems simultaneously

0.00

200.00

400.00

600.00

800.00

1000.00

1200.00

1400.00

1600.00

1800.00

2000.00

70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102

Evaporation in Yucatan Peninsula (1970-2002) (in mm)

increases

decreases

decreases

11 mm/anho

0

500

1000

1500

2000

2500

52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02

Precipitation in Yucatan Peninsula 1952-2002 (in mm)

decreases increases

decreases

Spatial distribution of temperature trends

Time trends in annual land-surface precipitation (1950-1993)

12

13

14

15

16

17

18

19

20

21

22

23

62

64

66

68

70

72

74

76

78

80

82

84

86

88

90

92

94

96

98

00

02

Te

mp

(°C

)

Maximum Temperature Southern Peruvian Andes (February)

Maximum Temperature Yucatan Peninsula (Annual)

y = -0.1x + 38.4

32

33

34

35

36

37

38

39

40

41

42

62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02

Te

mp

(°C

)