Global warming - University of Kentucky



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

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