Greenhouse Gases, Feedbacks, and Scenarios

What is the relationship between greenhouse gases and global climate change? 

Imperfect understanding of climate feedbacks is a major cause of uncertainty and concern about global warming.  How can the use of climate models help in the understanding of these uncertainties? 

With regards to the six emission scenarios, describe any evidence existing today that would suggest to you one or more of the scenarios may occur within the next 100 years.  What key uncertainties (climate forcings and feedbacks) would exist for these scenarios as a whole, or specific ones individually?

There are several gases which contribute to the greenhouse effect.  These gases are water vapor, carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons (CFCs).  These gases together contribute to what is known as the greenhouse effect.  The greenhouse effect occurs due to warming that results when the atmosphere traps heat radiating from Earth towards space.  This heat is trapped by the previously mentioned greenhouse gases.  The trapping of this heat causes a warming of temperatures on earth.

There are several climate feedbacks which we do not understand completely.  These include: Atmospheric factors (clouds and aerosols), Hydrosphere, Cryosphere, Lithosphere, and Biosphere.  Climate models can help us to understand these better by allowing us to simulate the change in each of these over a given period of time.  While a model may not be completely accurate, it can provide us with a possible scenario for the future.

Out of the six emission scenarios, I believe that scenario B2 is the most likely to occur within the next 100 years.  I believe this to be the most likely scenario due to the constant population growth without decline, and the emphasis on local, rather than global solutions to economic, social, and environmental stability.  The key uncertainties which will exist for all of the scenarios are atmospheric factors, hydrosphere, cryosphere, lithosphere, and biosphere.  I believe that these uncertainties would have the least impact on scenario A1T, which puts an emphasis on non-fossil energy sources.