In the last 100 years, since industrialization took off in now developed countries around the world, human activity has added close to 24 billion tons of carbon dioxide (CO2) per year to the naturally occurring amount of CO2 cycling through the earth's systems (roughly 800 billion tons). Atmospheric concentrations of CO2 are predicted around 32% higher than 150 years ago. Along with this additional CO2, the average global air temperature has risen roughly 0.5% Celsius, with the ten warmest years on record occurring since 1980. As this global warming occurs, scientists around the world are researching and hypothesizing the resulting change in climate that is likely to occur. This change in climate from global warming has primarily been linked to the increased amount of CO2, but also to other heat-trapping-gas emissions such as methane (CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFCs). Between 1987 and 1996, global atmospheric concentrations of both carbon dioxide and methane have increased by 4%, while nitrous oxide has increased by 2.2%. In addition, according to ice core data, the current global atmospheric concentration of carbon dioxide, at 360ppm, is thought to be the highest in 220,000 years of ice core data.

Car emissions are not solely responsible for increased levels of carbon dioxide in the atmosphere. Industrial factories, power plants, oil refineries and deforestation all contribute to the level of carbon dioxide. Of all types of fossil fuels, coal is the most carbon intensive, meaning it has the highest amount of CO2 emitted from each unit of primary energy*. In addition to coal (the principle fossil fuel used over the last century), oil and natural gas have also contributed to the volume of carbon emissions.

Strangely enough, carbon dioxide is considered the least effective greenhouse gas, compared to the others on a per mole basis, however, because if its high rate of increase, it is currently responsible for close to 60% of greenhouse action. As fossil fuel use emits a large amount of carbon dioxide into the atmosphere, the rate of fossil fuel increase in the future become critical: "The rate of increase during the period before 1973 was 4.3% per year; since then it has been about 2.5% per year. If we assume a 2% growth rate in the use of fossil fuels and an airborne fraction of 0.55, then the pre industrial level of CO2 will double to 550ppm by about 2053" *. Essentially, we need to curtail emissions of CO2 and other heat-trapping-gases immediately to prevent further human-induced global warming.

See chart : http://www.ucsusa.org/warming/gw.science.html

As of today, documented changes in climate include:

-a global mean temperature rise (night-time minimums increasing more than day-time maximums),

-the 10 warmest years on record since 1980,

-a rise in sea level of 10-25 cm due to thermal expansion of the oceans,

-a steady increase in the mean annual air temperature of Antarctica since the 1950's.

Scientists are currently working to determine the extent to which these changes can be attributed to human activity. Through the Intergovernmental Panel on Climate Change (IPCC), scientists and experts from around the world have combined research and theories on climate change in an attempt to provide more concise, objective answers for the general public. Climate change research, still in somewhat early stages, can be speculative and frequent to refinement, as scientists learn more about the earth's systems.   Greenpeace

Sources:

*Gates, David. Climate Change and its Biological Consequences. Sunderland, Mass. Sinauer Associates, c1993.

Hare, Bill. Fossil Fuels and Climate Protection: The Carbon Logic. Greenpeace International. (www.greenpeace.org).

Environment Canada: Climate Change - Indicator: Global atmospheric concentrations of greenhouse gases (www.ec.gc.ca/Ind/english/Climate).

The National Council for Science and the Environment. Morrissey, W.A. and Justus, J.R. Resources, Science, and Industry Division. The Congressional Research Service Issue Brief- Global Climate Change: Science and Policy, Sept. 19, 2000. IB89005.

Union of Concerned Scientists - The Science of Global Warming (www.ucsusa.org/warming/gw.science.html).