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Marian Wilkinson, Environment EditorMarch 23, 2009THE top government scientist advising on how to adapt the nation to climate change warns that Australia will be forced to abandon some coastal communities in a "planned retreat" because of rising sea levels caused by global warming.Andrew Ash, who leads the CSIRO's Climate Adaptation Flagship program, told the Herald that while some vulnerable coastal places could be protected by sea walls and levees, "there are going to be areas where that is not physically possible or it's not cost-effective to introduce any engineering solution and planned retreat becomes the only option".Warning that climate change was accelerating much more quickly than predicted, Dr Ash said state and local governments needed urgently to identify coastal land unsuitable for new residential development because rising sea levels and more frequent big storms would flood them with seawater.Federal and state governments would also need to rule out putting costly new infrastructure such as airport runways and bridges in vulnerable low-lying coastal areas."They need to be thinking now about what areas are vulnerable and what areas are likely to be unsuitable in the longer term for new residential developments because local governments are concerned about future liabilities," Dr Ash said.Scientists at Sydney University have previously identified vulnerable areas in NSW, including Narrabeen, Dee Why and Curl Curl on Sydney's northern beaches. Batemans Bay to the south and parts of Byron Bay in the north are also seen as particularly vulnerable.Dr Ash will press his warnings when he joins 500 scientists, industry figures and policy-makers, including Professor Ross Garnaut, in Perth this week for the climate change conference, Greenhouse 2009."The planning needs to start now," Dr Ash said. "That is a real challenge for us - getting it into the psyche of people, getting an ownership of the problem and having enough capacity to start exploring solutions to the problem."Dr Ash and other senior CSIRO scientists have just returned from the global scientific congress on climate change in Copenhagen, which heard that climate change impacts are tracking at the highest case levels predicted less than two years ago by the peak United Nations scientific body, the Intergovernmental Panel on Climate Change. These include projections on rising sea levels that are escalating as new scientific evidence shows the ice sheets of Greenland and Antarctica are melting more rapidly than predicted, as are many glaciers."Across the range of the main indicators of climate change, all are tracking at the top level of projections," Dr Ash said. "That is mirroring the fact that global greenhouse gas emissions are also tracking at the top end of the IPCC projections."Last month, the NSW Government released draft guidelines to consult with local governments, business and communities on how to prepare for sea-level rises of up to 40 centimetres by 2050 and 90 centimetres by 2100.Scientists at the Copenhagen conference said even these projections might be too low, with sea-level rise possibly going above one metre by 2100.Scientists point out that combined with storm surges, a rise in sea level of one centimetre can cause erosion effects 50 to 100 times greater in low-lying areas.The Federal Government plans to hold a national forum soon on climate change impacts on coastal communities. The Climate Change Minister, Penny Wong, will tell the greenhouse conference today that the Government will spend $20 million helping Pacific island countries and East Timor track the accelerating threat of climate change from sea level rise, storm damage and water shortages.