Climate change will have potentially devastating consequences for human health, outweighing global economic impacts, researchers said, calling for urgent action to protect the world's population.
"While we embark on more rapid reduction of emissions to avert future climate change, we must also manage the now unavoidable health risks from current and pending climate change," said Australian researcher Tony McMichael, who co-authored a study in the British Medical Journal.
"This will have adverse health effects in all populations, particularly in geographically vulnerable and resource-poor regions," he said.
Mr McMichael, from Australia's Centre for Epidemiology and Population Health, said increased wildfires, droughts, flooding and disease stemming from climate change posed a much more fundamental threat to human well-being than economic impacts.
A 2006 report by former World Bank chief economist Nicholas Stern said climate change had the potential to shrink the global economy by between five and 20 per cent, causing a similar impact to the Great Depression.
But Mr McMichael said climate shift would bring changes to the pattern of infectious diseases, the effect of worsening food yields and loss of people's livelihoods. While it was unlikely to spawn entirely new types of diseases, it would impact on the frequency, range and season patterns of many existing disorders, with between 20 and 70 million more people living in malarial regions by 2080, he said.
And the impact would be hardest in poor countries, said the researchers, including co-author Sharon Friel from the Australian National University, Tony Nyong from Nigeria's Jos University and Carlos Corvalan of the World Health Organisation.
"Infectious diseases cannot be stabilised in circumstances of climatic instability, refugee flows and impoverishment," Mr McMichael said. "Poverty cannot be eliminated while environmental degradation exacerbates malnutrition, disease and injury."
He said immediate decision-making was needed to involve health professionals in planning for the impact of climate change.
Kevin Parton, from Australia's Charles Sturt University, said the report was a wake-up call that the world needed to be doing more to eradicate diseases such as malaria.
"The health risks are massive, and the best way to mitigate them is to minimise the extent of climate change. Global community health is the climate change issue," he said.