adapted to HTML from lecture notes of Prof. Stephen A. Nelson Tulane
We know that we are adding greenhouse gases to the atmosphere.
By how much and at what rate are these gases changing the Earth's
Greenhouse gasses responsible for changing the Earth's temperature?
| Greenhouse Gases
| Gas and Effects
|| Relative Percentage
- Burning of Fossil Fuels
| 60 %
- Coal Mines
- Wetlands (Beavers?)
- Rice Patties
- Subpolar Soil and Wetlands (Methane Hydrate)
| 15 %
- Fire Extinguishers (halons)
- Industrial Solvents
- Spray Cans
| 12 %
- Unburned hydrocarbons from internal combustion engines
reacting with sunlight
- Artificial Fertilizers
- Disturbance of Soil
- Polluted Rivers and Estuaries
- Automobile exhaust
- Nylon Production.
| >5 %
In the charts shown below, we can see how the concentrations of these
gases have increased in the atmosphere during the last 250 years.
- In the last 1,000 years, the temperature has fluctuated by about
1.5° C in Europe. This change in temperature can have a large effect
on agriculture, especially in areas where the weather is marginal for
farming. In northern Europe, for example, killing frost during the
growing season or cool summers would mean that crops would be
inadequate to feed the population. During the period known as The
Little Ice Ages, famine resulted from long term crop failures. It has
been hypothesized that famine and the resulting weakened resistance of
the population in Europe were partially responsible for the deadly
Black Plague during the 1300's.
- The Earth's climate goes through a periodic long span fluctuation in
temperature, known as glacial periods or Ice Ages. The last such Ice
Age began approximately 110,000 years ago, and lasted until about
10,000 years ago. The glacial period reached its lowest temperatures
and the maximum advance of the glaciers about 20,000 years ago. As can
be seen from the chart shown below, carbon-dioxide contents of the
atmosphere are lower during the glacial (cold) periods and higher
during the interglacial (warm) periods.
- The most important factor for the development of glaciers is cool
summers. Cool summers are necessary to ensure that the snow doesn't
melt completely during summertime. Glaciers form when the snow left
over from the previous winter gets added to by new snow. Over
successive years of cold summers, when the snows do not melt
completely, new winters snow gets added on top of the previous years
snow, when the accumulation is thick enough a glacier develops.
- Glacier Ice, as it compacts, traps air within it. Newfallen snow has
about 90% pore space. The pores are filled with air. As the snow
compacts from the added weight of the new snow on top, some of this
air escapes; however, some of the air gets trapped within the ice
crystals that form from the compacted snow. Scientists can extract
this air, and can use it to determine the contents and temperature of
the atmosphere when the air was trapped within the ice. The
temperature is evaluated by measuring the ratio of oxygen isotopes.
Each summer as a result of melting and dust accumulation produces a
darker layer in the glacier. The diagram above was determined by
drilling in the Greenland ice cap. The gases were used to determine
the composition of the ancient trapped atmosphere. The dark layers
were counted to determine the age of the ice sampled. The oxygen
isotope ratios were measured to determine the local temperature. Using
this method, atmospheric data has been gathered for the last 150,000
Consequences of Greenhouse
- Increase in warming:
- Least effect in tropics.
- Greatest towards poles.
- Change in rain or snowfall:
- Wandering weather patterns.
- Increased Precipitation.
- Less rain in the summer in the U.S. midwest.
- Wetter in former Soviet Union.
- An increase in monsoon rains in India.
- Drier in Africa, China & Brazil.
- The intensity and number of storms will increase.
- The ocean currents may be modified
- Temperature on Earth is extensively modified by ocean currents.
Changes in the currents will result in changes in temperature over
- sea level rise 1-3 feet by 2100
- Expansion of water due heating.
- Melting of glaciers.
- Will result in coastal flooding.
- Natural habitats will be destroyed
- Forests will start dying off.
- Wild animals in these regions will be unable to migrate to a more
suitable climate. This is because of development and isolation.
- Agriculture may be helped or hurt.
- Depends on area - Siberia will be helped. Midwest U.S. will be
- Also depends on the ability of farmers to react fast enough to
changing climate conditions.
- Water for irrigation and human use may be inadequate in dryer areas;
groundwater reservoirs can only last so long. In some regions there
will be less rainfall
- Diseases common to warm regions will be able to expand to new areas
with the warming.
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