GLOBAL WARMING AND THE GREENHOUSE EFFECT

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1 GLOBAL WARMING AND THE GREENHOUSE EFFECT Our planet temperature is warming significantly due to human activities? OR Last few years warming is part of a natural global cycle?

2 1998 : The warmest year on record ( ) The warmest year of past thousand, based on tree rings

3 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

4 GREENHOUSE EFFECT The atmosphere traps longwave radiation and returns it to the surface Greenhouse gases (LWR absorbers): CO 2, water vapor Greenhouse liquid: Clouds (tiny water droplets)

5 IPCC: INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE It s a scientific intergovernmental body set up by the WMO (World Meteorological Organization) and by the UNEP (United Nations Environment Program) 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

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8 GLOBAL WARMING AND GLACIER SHRINKAGE 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 Mass balance: Difference between accumulation and ablation (melting and sublimation) A glacier with: Sustained (-) mass balance: will retreat Sustained (+) mass balance: will advance Glaciers monitored by IRD and South American institutions (Francou et al, 2005)

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

10 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 and along a transect from Alaska to Southern Chile (scenarios using CO2 levels) Traingles show highest mountains at each latitude) (Raymond et al, 2006)

11 Central (3300 m) y = 0.02x Southern (3800 m) Southern (4200 m) y = 0.05x y = 0.03x

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

13 AEROSOLS: COOLING EFFECT Mount Pinatubo eruption (Philliphines, 1991)

14 MOUNT PINATUBO ERUPTION (Phillipines) The volcanic eruption (June 1991) that cooled the planet The second largest volcanic eruption of the 20 th century Volcanic activity Particles and gases (SO 2 ) 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)

15 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

16 decrease of solar energy: 9% Antartica 10% USA 30% Rusia Antartic Arctic

17 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 C was observed in some parts of the U.S.

18 EFFECTS OF GLOBAL DIMMING Masking effects of global warming Less solar radiation Less evaporation Less energy to produce evaporation Less precipitation (Droughts) If we focus only in aerosol forcing: acceleration of greenhouse effects If we focus only in greenhouse gases: increase of droughts It s important to handle the two problems simultaneously

19 Evaporation in Yucatan Peninsula ( ) (in mm) decreases decreases increases Precipitation in Yucatan Peninsula (in mm) 11 mm/anho decreases 500 decreases increases

20 Spatial distribution of temperature trends

21 Time trends in annual land-surface precipitation ( )

22 T emp ( C ) Temp ( C) Maximum Temperature Southern Peruvian Andes (February) Maximum Temperature Yucatan Peninsula (Annual) y = -0.1x