GLOBAL WARMING

 

It is the human-induced increase in the average global temperature of the earth's surface. Certain gases in the atmosphere trap heat in the lower atmosphere (troposphere) and raise the average global temperature causing global warming.

 

THE EVIDENCE

 

1.  Global temperature:

Global average temperature increased steadily from 1880 to 1940 and then fell slightly between 1940 and 1975. It has risen sharply since 1975. The 5-year period from 1991 through 1995 was the warmest half century since 1860.

 

2.  Global Sea-level:

Between 1900 and 1990, global sea level has risen by 9-18 centimeters (3.5-7 inches).

 

GREEN HOUSE GASES

 

1)  Carbon Dioxide (C02):

Carbon dioxide is responsible for 50-60% of global warming from green house gases.

 

Main sources of C02:

    i)  Fossil fuel burning 75%

    ii) Land clearing (deforestation) and burning of wood 25%.

 

Developed countries produce about 70% of these C02 emissions (mostly from burning fossil fuels). USA alone account for about 22% of global C02 emissions, followed by China (12%), Russia (9.4%) and Japan (5%).

 

Ice core analysis reveals that at the beginning of the industrial revolution, the atmospheric concentration of C02 was about 228 parts per million. Between 1860 t0 1995, C02 concentration rose phenomenally to 360 parts per million, higher than any time in the past 150 years.

 

 

2)  Chlorofluorocarbons (CFC's):   

     CFC's deplete ozone layer and and contributes to global warming

Main sources:

    i)   Leaking air conditioners and refrigerators,

    ii)  Evaporation of industrial solvents,

    iii) Production of plastic foams and

    iv) Aerosol propellants.

 

 

3)  Methane (CH4): 

     Produced when anaerobic bacteria breaks down dead organic matter in moist places that lack

oxygen.

Main Sources:

      i)   Swamps and other wetlands,

     ii) Rice paddies, 

     iii) Landfills

     iv) Intestinal tracts of cattle, sheep and termites.

     v) Leaks in natural gas pipelines and incomplete burning of organic materials.

 

4)  Nitrous Oxide (N20)

Obtained from nylon production, the burning of biomass and nitrogen-rich fuels (especially coal), and from the breakdown of nitrogen fertilizers in the soil, livestock wastes and nitrate in contaminated groundwater. Traps heat in the troposphere and deplete ozone in the stratosphere.

 

TRENDS IN PAST GLOBAL TEMPERATURE

 

Past Temperature Changes:

 

Ÿ       Earth's average surface temperature has fluctuated over geologic time. During the past 800,000 years, several ice ages have covered the planet with thick ice. Each lasted for about 100,000 years and was followed by a warmer Interglacial period of between 10,000 - 12,500 years.

 

Ÿ       Last Ice Age occurred over 20,000 years ago and in the past 10,000 years, the earth has enjoyed the relative warmth of the latest Interglacial period called the Holocene.   

 

Past Water Vapor Levels

Ÿ       Studies show that over the past 160,000 years, water vapor level in the troposphere has fluctuated between 190 and 290 parts per million.

 

Ÿ       C02 concentrations correlated with estimated variations in the earth's mean surface temperature.

 

ARGUMENTS  AGAINST  GLOBAL  WARMING

 

1.   The consequences of the Greenhouse effect is not well understood.

 

2.   Scientists still disagree as to whether there is going to be significant temperature rise in the

      near future

 

3.  Global Temperature Data is available for only a few years (since 1846)

 

4.  Lack of temperature data for several locations (especially before 1900)

 

5.  Some local temperature changes are different from the global temperature

 

6.  Aside Greenhouse gases, Global Climate is affected by several factors

 

7.  Climate has never been stable but has naturally fluctuated in the past

 

 

ARGUMENTS  FOR  GLOBAL  WARMING

 

1.  Increases in Greenhouse Gases has matched the warming trend in Global temperature

 

2.  For the past Century, Scientists have observed a warming trend in Global temperature and a

     rise in sea level. The 10 hottest years on record have all occurred since 1980

 

3.  The rise in Global Temperatures over the past century has been too steep to consider as

normal.

 

4.  The size of observed warming has been consistent with the predictions of   current scientific

models

 

5.  The retreat of Glaciers and the warming of the Tundra Permafrost is clear evidence. A

     startling 2.5 C warming in Antarctica has been reported.

 

6.  Evidence from air trapped in 250,000 year old ice cores reveal that the level of Greenhouse

gases in the atmosphere has varied in the past but these variations have occurred

concurrently with temperature changes

 

7.   Greenhouse gases have been increasing since pre-Industrial times and concentrations are

      almost 30% more today

 

POSSIBLE IMPACTS OF GLOBAL WARMING

 

1.  Flooding of Cities and the Relocation of People:

2.  Shifts and Reduction in Food Production: 

3.  Dramatic Changes in Forest Species: 

4.  Changes in Lakes, Ponds and Wetlands:

5.  Human Health and Welfare:

 

DEALING WITH THE THREAT.

 

Different Viewpoints:

     1.  No Threat so do Nothing Strategy

     2.  Wait until something happens Strategy

     3.  Act as a Precaution Strategy

 

Suggestions for Slowing Down Global Warming:

 

1.  Increase the use of nuclear energy.

2.  Stopping the use of coal and relying on natural gas.

3.  Remove Government Subsidies to reduce fossil-fuel burning

4.  Adopt a massive Global Reforestation Program

5.  Adopt stringent Measures to Control Deforestation

6.  Set Global and National Limits on Green House Gas Emission.  

 

6.   Technofixes: 

a)   Add iron to the oceans to stimulate marine algae growth

b)   Put gigantic mirrors into space to reflect solar energy

c)   Inject sunlight-reflecting sulfate particulate into space