Global warming
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Kyoto protocol (treaty), 1997- reduce greenhouse gases to pre-1990 levels.
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Industrial nations sign on- except USA.
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Industry cites drag on economy (600,000 job losses per per.)
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USA: 2% pop. 25% greenhouse gases.
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India, China, former Soviet U.: 70% gases
Evidence of warming
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Northern latitudes warming faster: 5oC 1965- 2000.
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Warmest years past 600 years: 1998, 2002 based on tree rings, ice cores, corals,
historical record and instruments
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Current CO2 is 360 ppm. Maximum in past 400,000 yrs: 280 ppm.
Evidence of warming
• Volume of valley glacier decreasing (Switzerland, Rocky Mts., New Zealand, Alaska,
Caucasus Mts.)
• Continental sheets (Greenland, Antacrtica) also retreating.
• Permafrost thawing: flooding, landslides, ecosystem change
• Arctic ice melting
• Species of birds moving north, laying eggs earlier.
Evidence of warming
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Sea-level rise: 19th century: 12 cm;
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20th century.: 25 cm
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a) expansion of water- causes sealevel rise ; 24 cm/oC; 20 yr. time lag;
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b) melting of ice- causes sea level rise.
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Tundra melting: oil companies can drive only 100 days/yr (used to be 200)..
Possible causes of warming
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Natural: volcanic dust , natural variability in solar radiation (see Milankovitch theory).
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Manmade (anthropogenic): greenhouse gases; manmade aerosols
National Academy of Sciences
2001
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Earth has become warmer in past decades
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Due to burning of coal, oil, gas, wood
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Different latitudes affected differently
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Cause is unlikely to be natural
Likely effects
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Hydrologic cycle speeds up: more extreme weather (flooding, hurricanes, droughts).
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Globally: +2.5oC by 2050; ecosystems move north
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Rainfall increase (except mid-latitudes- drought)
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Less ice in N. hemisphere; Arctic warming
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Sealevel rise 5-40 cm by 2050
More effects
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Change in ocean circulation? – shut down of Gulf stream due to fresh water input from
ice melting.
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More disease in tropics
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Sea-level rise will affect developing nations more.
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Wineries in Canada!
Some industries actually recognize warming!
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Boeing, BP, United Tech., Lockheed, Maytag, Shell, Ford (hybrid SUV), Toyota
(hybrid auto).
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Exxonmobil: says warming maybe natural trend (see NewYork Times ads.).
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Oil here ‘til 2030.
Solutions to global warming
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Conserve energy, recycle.
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Alternative energy sources (nuclear, solar, wind, hydrothermal, fuel cells).
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Bury CO2 underground (“sequestration”).
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Seed ocean with iron powder- cause plankton to bloom –ocean absorbs CO2.
Causes of climate variations
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Milankovitch theory – changes in earth’s orbit around sun.
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1) Obliquity of earth axis – tilt (41,000 yrs)
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2) Eccentricity of earth’s orbit (100,000)
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3) Presession, wobble of earth’s axis (23,000).
When all three cycles coincide- Explains variations during last ice age very well