Climate Change Science
The challenges posed by climate change affect everyone around the world, and require concerted action if we are to avoid critical environmental, economic and social consequences.
While climate change is a natural process, it has been significantly accelerated by the emission of greenhouse gases primarily caused by the use of fossil-based fuels. It is generally accepted by the international science community that the world must reduce its emission of greenhouse gases by 60% of 2000 emissions by 2050 if we are to limit average global warming to 2oC. Greater global warming than this is expected to cause dramatic irreversible changes, such as the melting of the Greenland ice cap.
Greenhouse Effect
Climate change is the result of an enhanced greenhouse effect, resulting from human activities that release large volumes of carbon based gases. The greenhouse effect is an important natural phenomenon. Greenhouse gases absorb and re-radiate the sun’s warmth, and maintain the Earth’s surface temperature at a level necessary to support life. However, sound evidence confirms that human activities, particularly the use of fossil fuels (coal, oil and natural gas), broad scale deforestation, and land use changes, result in increases in the atmospheric concentrations of greenhouse gases (including carbon dioxide, methane and nitrous oxide). This is known as the enhanced greenhouse effect and is scientifically accepted as being primarily responsible for the rise in global temperatures recorded through the previous and current centuries.
Even a small change in atmospheric temperature will have a significant effect on our climate including changes in global rainfall, and extreme events such as storms, cyclones and droughts. ACT residents are already aware of the significant impact drought and bushfire can have on their community.
Scientific evidence shows that accumulated greenhouse gas emissions have already changed climate around the world and will continue to do so. The international policy focus and debate has shifted from simply mitigating the enhanced greenhouse effect to also addressing the climate changes that are already occurring. As such, policies developed by governments and business increasingly recognise that action on a number of fronts is necessary for communities to both slow the rate of change and also adapt to the changes that are already inevitable.
Greenhouse Gases
Approximately 30 gases qualify as climate-changing greenhouse gases due to their Global Warming Potential (GWP) and the quantity in which they are released. GWP is the concentration of the gas and is measured compared to carbon dioxide. Methane and Nitrous Oxide for example have a GWP equivalent to 21 and 310 Carbons respectively.
Figure 1. Difference between the greenhouse effect and the enhanced greenhouse effect. Diagram courtesy of the Australian Greenhouse Office. http://www.greenhouse.gov.au/science/qa/pubs/science-qa.pdf 
