Global Warming Notes

___Milankovitch Cycles______– periods in Earth’s history that coincide with ice ages reflecting an association with one or more cyclic patterns,

  • 100,000 year cycle – the orbit of the Earth changes from one that is mostly circular to one that is very elliptical
  • 41,000 year cycle – the angle of the Earth’s axis is different thus influencing temperature differences
  • 21,000 year cycle – where the Earth’s axis is tilted at a different angle at the aphelion producing other temperature changes

These cycles (along with the 11 year sunspot cycle) give credence to those who don’t believe in global warming – that the present warming trend is only part of one of these cycles.

Past temperature changes were analyzed by:

  • ___radioisotopes (half-life)______in rocks & fossils (dating back 2.9 billion years)
  • plankton & radioisotopes in ocean sediments (dating back 20,000 – 180 million years)
  • ____cores______from lake bottoms, bogs, & volcanic ash (dating back 2 million years)
  • ___ice core_____samples from ancient glaciers (dating back 440,000 years)
  • ___pollen______(dating back 500 – 11,000 years)
  • radioisotopes in coral (dating back 400- 130,000 years)
  • historical records (dating back several hundred years)
  • actual temperature measurements (dating back 150 years)

The Earth is blessed with a Natural Greenhouse Effect that keeps the Earth’s average temperature at 59oF instead of 0oF.GOLDIE LOCKS EFFECT: JUST THE RIGHT DISTANCE + NATURAL GREENHOUSE EFFECT.

Natural Greenhouse Effect

______CO2______H2O______are the two natural greenhouse gases found in the largest concentrations. They capture long wave infrared radiation that has been reradiated from the Earth’s surface and change it to heat and disperse it into the atmosphere. That, coupled with the evaporative processes from the ocean’s surface, keeps the Earth’s relative temperature stable.Methane isn’t as abundant but is MORE EFFICIENT at trapping heat and is the second most prevalent greenhouse gas being emitted in the United States.

Greenhouse Gases and their relative warming potential:

Greenhouse GasAnthropogenic Source

CO2Fossil fuel burning(burning one gallon of gasoline produces 20 pounds of CO2)

CH4Rice paddies, Landfills, Melting permafrost, COWS

N2OInorganic fertilizers

CFC’s Air conditioners, refrigerators

HCFC’s Replaced CFC sources

HFC’s Replaced CFC sources

HalonsFire Extinguishers

CCl4Cleaning solvent

Possible Effects of Global Climate Change:

  • Increase/decrease of precipitation in areas that receive adequate precipitation, leading to flooding or desertification
  • Change of growing seasons – beneficial for those needing a longer growing season, detrimental for those whose cycles depend upon other growing cycles getting them off-cycle
  • Increased growth of plants (C3 type – sedges, trees, 95% of all plants ) due to increased CO2
  • Decrease growth of plants (C4 type – corn, sugarcane, orchids, pineapples, cacti – adapted to tropical climates )
  • Increased severity of storms, drought, floods
  • Melting glaciers prompting sea level rise – displacing many of the world’s populations who inhabit coastal areas
  • Increase of vector borne diseases (malaria, etc) from ticks, mosquitoes with increased temperature
  • Change in growth of fish and shellfish and migration patterns due to increased temperature
  • Disruption of ocean currents – changing surface climates and loss of nutrient cycling from deep ocean currents
  • Acidification of oceans (decreased pH) leading to corrosion of coral reefs
  • CO2 + H2O H2CO3
  • THERMAL EXPANSION of oceans = sea level rise

Positive feedback systems associated with global warming and increased CO2 levels

  • Sea ice has an ______Albedo______(reflectivity) of 80%. If it melted then the darker ocean water would absorb more UV radiation thus increasing the atmospheric temperature.

  • The release of ___Methane______from permafrost, wetlands, and methane hydrates (used for natural gas supplies) will increase atmospheric temperatures

Negative feedback systems associated with global warming and increased CO2 levels

  • The formation of low, thick stratus __clouds______from aerosols and excess evaporation will block more sunlight and thus decrease atmospheric temperatures.
  • Increased ___photosynthesis (CO2 absorption)______by young or fast growing plants would decrease the CO2 in the atmosphere which would decrease atmospheric temperatures
  • Increased temperatures increases ___algae/phytoplankton______growth in the oceans which will absorb more CO2 reducing atmospheric temperatures