Over the last 30-40 years, climatologists have been noting changes in the earth’s climate that they believe are the result of unprecedented increases in the levels of greenhouse gases in the atmosphere, mainly linked to the processes of industrialisation, and associated increases in production and consumption over the last 50-100 years.

Establishing the science

In 1988, the United Nations established the Intergovernmental Panel on Climate Change (IPCC), a scientific intergovernmental body tasked with reviewing and assessing the most recent scientific, technical and socio-economic information produced worldwide related to climate change. Over the last 20 odd years, the IPCC has produced a number of assessment reports that provide the world with a clear scientific view on the current state of climate change and its potential environmental and socio-economic consequences, notably the risk of climate change caused by human activity. The comprehensive information in the IPCC reports is based on peer-reviewed, published scientific evidence from relevant experts from all regions. Each new assessment report is probably the most scrutinised scientific document in the world, and reflects a progressive strengthening of our understanding of climate change.

In 2007, the IPCC presented the Fourth Assessment Report, concluding that global warming is ‘unequivocal’ with multiple lines of evidence showing that the earth’s average surface temperature has risen nearly 0.76°C since 1850, the earliest year for which we have reliable records. [[Because these gases stay in the atmosphere for many years and continue to have an insulating effect, scientists tell us that we are locked into at least a further [[1-2]] degrees increase.]] Further, the report found that it is ‘very likely’ that human activity has been the main driver of rising global temperatures since the 1950s. (It is important to note that the term ‘very likely’ is used in a precise scientific context that reflects a 96% certainty that the causes of observed global warming are related to human activity.)

How the climate is changing

While the numbers above may seem small, their impact is much greater than just a global warming of temperatures by 1-2 degrees. This is firstly because this amount is just an average - the changes in temperature is unevenly distributed across the globe Some places around the world will experience much greater increases than this and some places will actually experience a DECREASE in temperatures.

This phenomenon of cooling and warming at the same time is [partly?] explained by the effect that an average global warming has on ocean temperatures and currents. As the air and land temperatures warm, so too does the average ocean temperature. The increased air and ocean temperatures causes accelerated melting of the ice in the arctic and Antarctic, resulting in an increase of cold water flowing into the oceans. The colder waters interact with the warmer waters to change the patterns of ocean currents, which sees some of this colder water flowing to places that in past have experienced warm ocean currents. As ocean temperatures mediate coastal land temperatures, the colder waters will cause colder temperatures.

Changing air and water temperatures also affects the weather. As ocean currents change this affects the air currents that flow above the oceans, changing cloud formation and wind patterns. The overall effect of these changing air currents is that most places around the world will actually experience much less frequent rain fall. However when rain does occur, it will happen with much greater intensity. This leads to a pattern of both droughts and floods. It also means that sometimes actual rainfall seasons will change, with dry weather during traditional wet seasons, and very wet weather during traditional dry seasons. The main effect though is to make the rainfall very unpredictable based on past experiences. Changing rainfall patterns also have an effect on traditional water catchment areas and existing river systems, which can affect previously reliable sources of fresh water.

A third effect of changing water temperatures and currents is an increase in the frequency and severity of tropical storms, such as cyclones (what about tornadoes and tsunamis? or are tsunamis only from earthquakes?)

Sceptical arguments

The above impacts are not just predictions but things that are being observed right now around the world. However there is still a significant and often vocal body of people who are either sceptical of climate change science or outright deniers.

The prominent people amongst this group are rarely climatologists or even scientists at all - they are generally social scientists such as economists, politicians, people connected with big business or social commentators. While there are a smattering of scientists among this group of people, research by (?) has found that 97% of published climatologists believe in the existence of human-induced climate change. That is, 97% of all scientists whose field of expertise is climate, and who have gone through the process of having their research peer-reviewed by other qualified scientists and published in a scholarly journal believe that climate change is happening and that it is directly linked to human activity. Further research (by WWF?) has shown that of the sceptical scientists, none of these have been published in a scholarly journal, and over (X%) have links to conservative think tanks that receive substantial funding from fossil fuel industries.

Unfortunately the science of climate change is most often presented in the media as a 'balanced debate' between believers and sceptics, giving the impression that the scientific jury is still out, rather than accurately portraying the almost total consensus on the science, with only the tiniest minority of dissenters.

More information

For further scientifically sound information, see the following sites:

• The Intergovernmental Panel on Climate Change (IPCC) is an international body that assesses scientific, technical and socio- economic information on climate change, its potential impacts, and options for adaptation and mitigation. Summary and full reports are available from the website on the Physical Science Basis of Climate Change; Climate Change Impacts, Adaptation and Vulnerability; and Mitigation of Climate Change.
• Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) has contributed greatly to climate change research, both domestically and internationally. Reports are available from the website on Impacts of Climate Change in Australia; Benefits of Early Action on Climate Change; Critique of Global Warming Swindle; Emission Trading; and The Future of Energy in Australia.
• RealClimate, a commentary site on climate science by working climate scientists for the interested public and journalists. The site aims to provide a quick response to developing stories and provide the context sometimes missing in mainstream commentary. The discussion is restricted to scientific topics and will not get involved in any political or economic implications of the science.
• The Climate Institute website, has some great "climate myths" pages on, addressing some of the arguments made by climate change sceptics. Also worth a look is Skeptical Science, which ‘gets sceptical about global warming scepticism’.
• The National Academies' (USA) "Understanding and Responding to Climate Change" brochure, 2008 edition. The brochure highlights findings and recommendations from the National Academies’ reports on climate change.

Information derived from Australian Department of Climate Change White Paper, December 2008, www.climatechange.gov.au