Climate Change and Carbon Dioxide Plus Other Greenhouse Gases

(Source: Neftel, A., H. Friedli, E. Moore, H. Lotscher, H. Oeschger, U. Siegenthaler, and B. Stauffer. 1994. Historical carbon dioxide record from the Siple Station ice core. pp. 11-14. In T.A. Boden, D.P. Kaiser, R.J. Sepanski, and F.W. Stoss (eds.) Trends'93: A Compendium of Data on Global Change. ORNL/CDIAC-65. CarbonDioxideInformationAnalysisCenter, Oak Ridge National Laboratory, Oak Ridge, Tenn.U.S.A. and Keeling, C.D. and T.P. Whorf. 2006. Atmospheric CO2 records from sites in the SIO air sampling network. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.)

It is thought that these large temperature fluctuations are triggered byvariations in the earth's orbit that change the amount of energy from the sun that reaches us. However, on their own, these cycles are not enough to explain the changes in temperature.

The full explanation seems to be that the small change in temperature caused by the changing orbit are amplified by natural processes on earth. These cause CO2 to be released from the oceans and the biosphere, causing an increased greenhouse effect.

Therefore there is a connection between increases in carbon dioxide levels and temperature increases and decreases.

Sources of Carbon Dioxide

The greatest natural source of carbon dioxide is animal respiration, though some scientists believe it to be volcanoes.

The greatest anthropogenic source of carbon dioxide is the burning of fossil fuels which according to many scientists dwarfs that of volcanic eruptions.

Sinks of Carbon Dioxide

Carbon dioxide is utilized by plants.

It is also sequestered (locked away) by the ocean.

Methane

  • Methane is a greenhouse gas.
  • Natural sources of methane gas are decomposing material.
  • Man enhanced sources of methane include livestock, termites and landfill decomposition.

Nitrous Oxide

Natural sources include bacterial decomposition of nitrogen containing materials.

Human sources include fertilizers, manure, sewage and car exhaust.

Ozone

Damage to the ozone layer

Ozone is oxygen that contains molecules that have 3 oxygen atoms O3.There is a layer of ozone high up in the atmosphere which shields the Earth from the sun's harmful UV rays, these rays can lead to an increase in skin cancer. The ozone is present in very small quantities but it is enough to absorb the UV rays preventing them reaching the surface.

Concentrations of ozone appear to be dropping in certain areas of the world. The cause of this reduction was thought to be man-made.

CFCs are chemicals that contain the element chlorine and can destroy ozone. They are often called halocarbons.

CFCs were once used as a propellant in aerosol cans.

It takes a long time for the damage of CFCs to take place, so it can be many years before a molecule of CFC can make its impact. Also it then can take many years for changes to environmental policy to show any results!

Ozone as a Greenhouse Gas in Global Warming

However, ozone is also a greenhouse gas.

By reducing ozone, we would temporarily cool the stratosphere (the top of the atmosphere) which could through chemical reactions lead to the production of more chlorine.

If you are REALLY interested in this reaction you might want to google it.

BUT the end result is more chlorine which means less ozone which means more holes in the ozone later.

Other Sources of Ozone

Ground level ozone is produced between sunlight and vehicle exhaust. Usually from hydrocarbons (chemicals with both hydrogen and carbon) and nitrogen oxides. This increases the amount of greenhouse gases, but at a level too low to be useful for the atmosphere so it warms the surface instead.

Incidentally ozone is also very bad for you to inhale, as it is somewhat damaging to the lungs.

Carbon Dioxide and Other Greenhouse Gases

Greenhouse gases can interact with each other.

Increases more than one can have a greater impact.

For example, water vapour and carbon dioxide interact with each other. Carbon dioxide can lead to more water vapour through warming, but more water vapour can both lead to more warming or less warming depending on cloud formation.

Hence the complexity of climate modeling.

Different greenhouse gases have the ability to affect global warming. See table 8.5 in the text.

Why do CFCs have such a huge potential to impact global warming?

Class Activity

So whether or not global warming is human made, or merely human enhanced, we know that adding extra greenhouse gases can damage the environment.

How can we use less greenhouse gases on a daily basis?

Brainstorm with your neighbour 5 ways you could personally reduce greenhouse gas emissions.