Seasonal Climate Outlook Message for May to August 2007

The bottom line

Climate Change Dave McRae Qld Climate Change Centre of Excellence 21st May 2007

As it is getting a lot of media coverage I thought I'd do a brief background on the greenhouse effect and climate change. Firstly as our climate is influenced by natural phenomena and human induced environmental changes it will always be in a state of change.

The greenhouse effect that is often referred to as part of global warming is a natural phenomenon. Naturally occurring greenhouse gases such as water vapour, carbon dioxide, methane and nitrous oxide trap some of the heat radiated by the earth's surfaces after being warmed by incoming solar radiation.

Similar to the effect of a greenhouse this keeps surface temperatures higher than otherwise would be the case warming the atmosphere by about 33 degrees Celsius (from minus 18 degrees to plus 15 degrees). It is this greenhouse effect that makes earth habitable for humans.

However there is an increasing body of evidence www.ipcc.ch/ that shows the burning of fossil fuels such as coal and oil for energy production and transport and through changing patterns of land use (such as urbanisation) has lead to an increase in carbon dioxide levels and other greenhouse gases in the atmosphere. This has enhanced the Earth's natural greenhouse effect and resulted in a warming (and drying) trend in many areas.

Other natural phenomena that influence our climate include the annual cycle, El Nino/Southern Oscillation, Pacific Decadal Oscillation, North Atlantic Oscillation, volcanic eruptions, fluctuations in solar irradiance, changing orbital cycles and variations in ocean, land and polar ice.

Human induced or anthropogenic drivers of climate change include changes in land use, urbanisation, and anthropogenic sources of greenhouse gases, aerosols and other pollutants.

It is therefore difficult to place the blame for climate change on one single factor (such as methane from cows). What is more important is to consider is what impact climate change (regardless of the cause) will have on business, agriculture and regional communities.

New joint CSIRO and Bureau of Meteorology regional climate change projections are due to be released in October. These will include projections for rainfall and temperature downscaled to a regional scale. This will hopefully provide more relevant information than is currently available.

Current CSIRO climate change reports are available at www.dar.csiro.au/impacts/consult.html Queensland climate change projections are available at www.longpaddock.qld.gov.au