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