Change in the Wind: Using a Range of Climate Models, the Climate Impact Group from CSIRO Atmospheric Research Has Predicted Significant Changes in Temperature, Rainfall and Evaporation in the Next 100 Years
Pyper, Wendy, Ecos
Using a range of climate models, the Climate Impact Group from CSIRO Atmospheric Research has predicted significant changes in temperature, rainfall and evaporation in the next 100 years.
Wendy Pyper looks at what's in store for Australia this century and at national and international efforts to curb climate change.
The Earth's energy balance is finely tuned. Sunlight passes through the atmosphere, warming the Earth's surface, while the land and oceans release energy to the atmosphere as infrared radiation. Water vapour, carbon dioxide and other gases absorb some of this radiation, warming the lower atmosphere, while the rest is released into space. Without the heat-trapping ability or `natural greenhouse effect' of these gases, the Earth's surface would be a chilly -- 18 [degrees] C, rather than the comparatively tropical 15 [degrees] C average we now enjoy.
Since the industrial revolution and the expansion of agriculture, however, copious quantities of carbon dioxide and other greenhouse gases -- methane, nitrous oxide, ozone, halocarbons and sulfur hexafluoride -- have been pumped into the atmosphere. This has led to increased trapping of infrared radiation and greater warming in the lower atmosphere.
During the 20th century, this warming contributed to a 0.6 [degrees] C temperature increase and a 15cm rise in sea levels (due to the expansion of water when heated). This `enhanced' greenhouse effect is often referred to as climate change or global warming. Scientists expect that continued increases in greenhouse gas levels will lead to further global warming and regional climate change.
In 1997, industrialised nations made an historic, collective agreement to reduce greenhouse gas emissions to 5.2% below 1990 levels by between 2008 and 2012. This agreement, the Kyoto Protocol, placed issues of climate change mitigation firmly on the international political agenda. But the agreement began to unravel earlier this year when the United States announced its withdrawal from the initiative.
International climate change negotiators resuscitated the agreement at a meeting in July, when they agreed on most of the key political issues stalling its implementation. But according to the executive director of the Australia Institute, Dr Clive Hamilton, much of the original Kyoto Protocol has been re-interpreted, such that the emission reduction targets enshrined in the protocol will be less effective in reducing greenhouse gas emissions.
`Under a "business-as-usual" scenario, emissions in industrialised countries are expected to be 25-30% higher in 2012 compared with 1990 levels. While the protocol was expected to restrict emissions to about 5% below 1990 levels, the deal done in Bonn will mean they are stabilised at 1990 levels,' Hamilton says.
`The re-interpreted Protocol also allows countries to meet these targets largely through carbon sinks -- reforestation, new plantations and changes in agricultural and forestry practices -- as an alternative to reducing fossil fuel emissions.'
Stabilising carbon dioxide
Despite the `watering down' of the Kyoto Protocol, Kevin Hennessy from CSIRO's Climate Impact Group, says it is an important first step in reducing the greenhouse gases that are contributing to global warming. It also sends a signal to industry that fossil fuels are not the only way to make the world go round. In its current form, however, the protocol will have little impact on moderating future climate change.
Hennessy says many gases have long atmospheric life times, so concentrations of gases continue to rise, even when emissions decrease.
`Imagine you're filling a bucket with water from a hose, and that the bottom of the bucket has two pin holes that allow some of the water out,' he says.
`The two pin holes represent carbon dioxide sinks, which are our oceans and plants. They're able to absorb a lot of carbon dioxide, but not enough to compensate for the amount we're pumping in. …