The Age, January 31, 2012
A leading Australian disease expert says prompt action on climate change is paramount to our survival on earth.
Epidemiologist Tony McMichael has conducted a historical study that suggests natural climate change over thousands of years has destabilised civilisations via food shortages, disease and unrest.
"We haven't really grasped the fact that a change in climate presents a quite fundamental threat to the foundations of population health," Professor McMichael, from the Australian National University, said.
"These things have happened before in response to fairly modest changes to climate.
"Let's be aware that we really must take early action if we are going to maintain this planet as a liveable habitat for humans."
In a paper published this week in the Proceedings of the National Academy of Sciences, Professor McMichael argued the world faced extreme climate change "without precedent" over the past 10,000 years.
"With the exception of a few downward spikes of acute cooling due to massive volcanic eruptions, most of the changes have been within a band of about plus or minus three-quarters of a degree centigrade," he said yesterday.
"Yet we are talking about the likelihood this century of going beyond 2 degrees centigrade and quite probably, on current trajectory, reaching a global average increase of 3 to 4 degrees."
Professor McMichael's paper states that the greatest recurring health risk over past millennia has been from food shortages, mostly caused by drying and drought.
Warming also leads to an increase in infectious diseases as a result of better growth conditions for bacteria and the proliferation of mosquitoes.
Drought can also result in greater contact with rodents searching for scarce food supplies.
He said that, while societies today are better equipped to defend themselves physically and technologically, they lack the flexibility smaller groups had in the past.
He said that was partly because the world was now "over populated", so there are fewer areas available to retreat to.
Populations are also increasingly packed into large cities on coastlines, which are particularly vulnerable to extreme weather events.
Professor McMichael has been examining the impact of climate change on population health for 20 years and said it was not easy to raise awareness of the risk.
"Most of the attention has been of a more limited shorter-term kind relating to things around us like the economy, our property, infrastructure and risks to iconic ecosystems and species."