DEATHS from heat stress among the elderly are likely to double in Sydney by the middle of the century because of climate change, and the number of people hospitalised because of air pollution is likely to treble, scientists from the CSIRO and the Bureau of Meteorology are predicting.
Modelling by Dr Martin Cope and his team has confirmed reports that heat-related deaths in Sydney will increase significantly, rising from about 150 to 200 to between 300 and 400 by 2060.
That is without considering demographic changes, the increasing number of people who will be over 65, Dr Cope said in Perth, where he will address the Greenhouse 2009 conference on climate change today.
Dr Cope's team looked at what would happen in 2060 in Sydney where climate change is likely to increase the number of days when the temperature will rise above 30 degrees.
In western Sydney the very hot days are likely to increase from 40 days to 45 to 50, and closer to the city the hot days are likely to rise from about 24 days to 30 days.
This would increase fire risk and air pollution, said Dr Cope. At higher temperatures the polluting compounds from sources such as motor vehicles or bushfires react and generate ozone. High smog levels can trigger problems such as asthma, bronchitis and emphysema.
The study looked in detail at the health effects of increased air pollution.
Photochemical smog, largely from vehicle emissions, leads to about 250 people a year presenting at hospitals. Dr Cope said this was likely to treble with climate change to about 750 people.
The increased heat would cause an increase in pollution as it expanded in the atmosphere. The dangerous days would be those where the temperature rose to more than 30 degrees and there was no wind to disperse it.
Dr Cope's work is assisting the NSW Department of Climate Change as it plans for an increase in health problems from climate change and for ways to address the increase in pollution. "It's important we take steps to mitigate it," he said.
Scientists from the CSIRO also released research at the conference linking changes in Indian Ocean temperatures with major bushfires in Victoria.
Dr Wenju Cai said 11 of the last 16 major bushfires in Victoria were linked with a see-sawing temperature pattern called the Indian Ocean Dipole. These included the Ash Wednesday fires of 1983 and this year's Black Saturday fires.
The dipole brings dry weather to southern Australian in winter and spring, setting up the conditions for bushfires. Only one of the past 16 bushfires was preceded by an El Nino event without a dipole. El Nino was previously thought to be the dominant influence on drought patterns in Australia.
There is a major research effort in Australia to understand the influence of the Indian Ocean Dipole on our weather. From 2006 to 2008 there were three consecutive dipole events, which was unprecedented. Dr Cai said these dry years led to a major decline in soil moisture in Victoria in the lead-up to last month's fires.
Modelling for Dr Cai's study indicated that an increased frequency in dipole events appeared to be linked to climate change.