This is an extract from The Science of Climate Change — Questions and Answers, published by the Australian Academy of Science and distributed to members of parliament, every local government authority in Australia and every Australian high school, in August 2010. Crikey will be running a series of extracts, including canvassing common myths.
Climate change will have significant impacts on our society and environment
Historically, the Australian climate has been highly variable. This variability makes it challenging to predict the future consequences of human-induced climate change. However, climate models and past experience provide some guidance. By around 2030, Australian temperatures are likely to be a half degree or more higher than 1990 and the frequency of hot days and nights will have increased. Sea level is expected to be about 15 centimetres higher and there is some evidence to suggest that tropical cyclones will become more severe, but less frequent. It is likely that future rainfall patterns across Australia will be different from today.
Changes in rainfall patterns are hard to predict: regional rainfall projections from different climate models (or between different runs of the same model with different starting conditions) are frequently quite different from one another. Nevertheless, some future trends are projected fairly consistently, including increases in rainfall in northern Australia and decreases in Victorian and southwest WA coastal regions.
The projections for rainfall trends across the entire Murray-Darling basin remain uncertain. It is likely that higher temperatures and changing patterns of wind and rainfall will change the patterns and frequency of extreme fire weather, and also lead to more heat related deaths and fewer cold-related deaths. Farming in Australia is vulnerable to climate change but skilful management is expected to be able to alleviate some of this vulnerability.
Higher CO2 levels, fewer frosts and changed rainfall patterns may be beneficial to agriculture in some parts of Australia, but decreases in rainfall in other Australian regions are likely to have a detrimental effect on agriculture. Warmer ocean temperatures will lead to further changes in the distribution of marine animals and plants, with some tropical fish moving progressively southward. As a result of increased CO2 in the atmosphere, oceans will become more acidic and, in combination with the higher temperatures, coral bleaching events are likely to become more frequent and severe around northern Australia.
Sea level will increase, inundating parts of the Kakadu freshwater wetlands and causing increased coastal flooding, with consequent change to sandy coastlines. As sea levels rise, coastal infrastructure around Australia will become more susceptible to damage. Tourism may be adversely affected, in part due to the sector’s dependence on natural assets and the built environment, both of which are vulnerable to the physical impacts of climate change.
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The impact of climate change on plants and animals will be variable. Habitat will expand for some species, while for others it will contract. However, the inability of many species to migrate as a result of both land use change and habitat fragmentation means that biodiversity is likely to decline overall, in line with observed global trends. Higher temperatures on the forested mountaintops of north-east Queensland, for example, may exceed the heat tolerance of some endemic species in the wet tropics, resulting in their extinction.
Climate change will exacerbate the impacts of other stresses
The world’s population is approaching seven billion people, and is expected to increase to around nine billion by mid-century, with two thirds of the world’s population living in the Asia-Pacific region.
This population growth will place additional stress on the planet and its people. For example, half of all readily available fresh water is already appropriated for human use. Without major changes to population growth policies, land use, city development, and economic and social systems, the additional potential burdens of climate change impacts could lead to social unrest across large parts of the world. Further pressures arise because there is now little room for many populations to relocate in response to climate change. These factors are likely to affect developed as well as developing nations. The recent global financial crisis has demonstrated how interconnected the world has become. It is also dependent on a finite resource base.
All of these factors demonstrate the need for an integrated approach to understanding how a sustainable planet can be attained in the presence of population pressures, risks from climate change, and other stresses.
Future impacts are expected to be more severe
If emissions continue unabated, current mid-range estimates are for 4.5°C higher global average temperatures by 2100, which would mean that the world would be hotter than at any time in the last few million years. Sea level would continue to rise for many centuries. The impacts of such changes are difficult to predict, but are likely to be severe for human populations and for the natural world.
The further climate is pushed beyond the envelope of relative stability that has characterised the last several millennia, the greater becomes the risk of passing tipping points that will result in profound changes in climate, vegetation, ocean circulation or ice sheet stability.
*The Australian Academy of Science, which represents Australia’s foremost scientists, provides scientific advice to policy makers and promotes excellence in Australian science, has devoted considerable resources to untangling the science of climate change and presenting it in a simple and easily understood format. The full report can be downloaded here.