What is Climate Change?
The natural greenhouse effect warms the planet and allows humans to live on the Earth. For millions of years, water vapour, carbon dioxide, methane and other greenhouse gases have occurred naturally, heating the atmosphere and making Earth habitable.
However, human activities, predominately the burning of fossil fuels, intensive agriculture and land clearing, are causing greenhouse gas concentrations to rise above natural levels, further heating the planet. This is called the enhanced greenhouse effect.
As the concentrations of these gases in the lower atmosphere grows, global temperatures rise, causing changes to weather conditions worldwide. The enhanced greenhouse effect is often referred to as global warming or climate change.
We need to reduce greenhouse gas emissions
Throughout history, the Earth’s climate has fluctuated naturally– from seasonal variations to sweeping shifts on geological time-scales, like ice ages. However, climate change currently occurring is linked to the buildup of greenhouse gases in the atmosphere from human activity.
Atmospheric concentrations of carbon dioxide, a key greenhouse gas, are higher now than at any time in the last 420,000 years. These raised levels correspond closely to changes in fossil fuel burning and land clearance.
Emissions of greenhouse gases have risen due to increasing demands for energy, associated with industrialization and growing populations, and as a result of changing land use and human settlement patterns.
Impacts of climate change
A majority of the world's scientists agree that human activities have resulted in observed increase in global average temperatures, particularly since the middle of the 20th century.
Recent data indicates that the global mean temperature has increased by between 0.2 and 0.6°C since the late 19th century, while Australian average temperatures have increased by 0.8°C.
Earth's average temperature might increase by up to 5.8°C over the next 100 years, if greenhouse gas concentrations continue to increase.
As the average global temperature rises, it will lead to other changes in weather. Storm patterns and severity might increase, sea levels will rise, and floods and drought may become more frequent and more severe.
Some changes to the climate are inevitable – even if we stop emitting greenhouse gases now, the gases we have already released will have an effect. However, we must do everything we can to avoid further changes, and to adapt to the impacts of climate change.
The scientific consensus
The Intergovernmental Panel on Climate Change (IPCC) was established by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess scientific, technical and socio-economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation.
The IPCC's Fourth Assessment Report (2007) concludes that global warming has accelerated in recent decades, and there is new and stronger evidence that warming over the past 50 years is attributable to the increase in greenhouse gas emissions associated with human activities.
The Fourth Assessment report has been released in three parts, with a final synthesis report due later this year. Scientists from all over the world, contributed to the findings discussed in the Fourth Assessment Report. To view each working group's report click on the working group's title below:
Working Group I - "The Physical Science Basis" (released February 2, 2007)
Working Group II - "Impacts, Adaptation & Vulnerability" Summary for policymakers(released April 6, 2007)
Working Group III - "Mitigation of Climate Change" Summary for policymakers (released May 4, 2007)
Visit the IPCC website at www.ipcc.ch
The economics of climate change
According to the most comprehensive account of the economics of climate change ever published, the review concludes that unabated climate change risks raising average global temperatures by over 5°C from pre-industrial levels, transforming both the plant’s human and physical geography. Unabated climate change would cost at least 5%, and up to 20%, of global GDP annually. In contrast, costs of mitigation activities could be limited to 1% of global GDP annually.
The review labels climate change the greatest market failure ever seen- arguing that tackling climate change is the pro-growth strategy, and that ignoring it will ultimately undermine economic growth.
Climate Change Impacts
Climate change will affect most regions in the world. There is growing understanding of the potential impacts of climate change.
Adaptation to Climate Change
Integrated Water Risk and Crisis Management Initiative
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