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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
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Central (3300 m)
y = 0.05x + 15.73
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Southern (3800 m)
y = 0.03x + 13.58
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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
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Evaporation in Yucatan Peninsula (1970-2002) (in mm)
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11 mm/anho
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Precipitation in Yucatan Peninsula 1952-2002 (in mm)
decreases increases
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Spatial distribution of temperature trends
Time trends in annual land-surface precipitation (1950-1993)
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Maximum Temperature Southern Peruvian Andes (February)
Maximum Temperature Yucatan Peninsula (Annual)
y = -0.1x + 38.4
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