(Source: o2 Western Australia)
Kevin Hennessy (Climate Impact Group, CSIRO Atmospheric Research) provided an answer to one of the most common questions: how do we know the climate change we are experiencing is man-made rather than natural. Kevin's response is:
"Climate models driven by scenarios of greenhouse gas ans aerosol (small particle) emissions estimate a rise in temperature of 1.4 to 5.8 degrees by 2100 assuming no actions to reduce climate change. While this is comparable to previously occurring climate change, it is occurring at an unprecedented pace and the changes would affect a larger and less mobile population." (emphasis added).