Climate Change

  1. There is wide agreement that human activity is changing the Earth's climate.
  2. The wide variety of human activity means there are many effects.
  3. Some of activities have confounding results.

Global Warming (greenhouse effect)

  1. An increase in a natural warming process caused by the atmosphere absorbing heat from the Earth's surface.
  2. An analogy is drawn to the warming of a greenhouse in sunlight.
  3. Gases that create this effect include H2O vapor, CO2, and methane (CH4).
  4. Human activity will double CO2 by 2060 due to burning of fossil fuels and deforestation.
  5. Humans also are increasing the levels of other greenhouse gases.
  6. The anticipated effect will be warmer global temperatures.
  7. Climate models and evidence from earlier shifts in the planet's climate suggest that a wide range of possibilities exist (including episodes of widespread cooling and glaciation).
  8. Ocean temperatures are also rising.
  9. Dust from desertification and SO2 reduce the amount of sunlight hitting the Earth's surface. This may reduce global warming.

Ozone Depletion:

  1. Ozone is a form of oxygen (O3)
    1. O3 absorbs dangerous ultraviolet (UV) rays from the sun.
    2. UV can break the bonds in DNA. O3 protects life on Earth.
    3. There is a thin layer of ozone in the lower stratosphere (17 km - 25 km).
    4. At ground level, ozone is a pollutant that causes lung irritation.
  2. Chlorofluorocarbons (CFC):
    1. Were used in refrigerators, air conditioning, aerosol propellants, plastic foam packing materials and a variety of industrial applications.
    2. Released at the Earth's surface, CFCs migrate to the stratosphere where UV light releases the chlorine atoms.
    3. Chlorine acts as a catalyst that turns O3 back into O2. One chlorine atom can destroy over 100,000 ozone molecules.
    4. CFCs released already will continue to act on the ozone levels for approx. 50 years.
  3. There has been a 50% thinning of the ozone layer in the stratosphere around the poles.
  4. Over the U.S., ozone levels have fallen 5-10%.
  5. The Montreal Protocol of 1989 was a treaty to eliminate the use of CFCs by 1996.


Evidence from glacial ice cores indicate that the climate of the last 10,000 years has been more moderate than previous millennia.