Doctors have said that climate change will imperil health through malaria, cholera, heatwaves and hunger, but many problems can be eased or avoided if countries make wise policy choices.
In a series of papers issued ahead of the UN climate conference in Copenhagen, experts challenged governments to factor in public health when conceiving a battle plan for global warming.
"In view of the trillions of dollars likely to be spent on greenhouse-gas mitigation in the coming decades, the relatively small resources needed to guide investments along paths bringing the world closer to its health and climate goals would be money well spent," they said.
The reports were published by the British medical revue The Lancet in the runup to the December 7-18 showdown, which aims at building a planet-wide pact on climate change from 2013.
"Policymakers have been slow to recognize that the real bottom line of climate change is its risk to human health and quality of life," World Health Organisation (WHO) Director General Margaret Chan said in a commentary.
"Malnutrition, and its devastating effects on child health, will increase.
"Worsening floods, droughts and storms will cause more deaths and injuries. Heatwaves will cause more deaths, largely among people who are elderly.
"Finally, climate change could alter the geographical distribution of disease vectors, including the insects that spread malaria and dengue."
The Lancet file said policymakers could boost both the environment and public health through "careful selection" of actions to curb carbon.
It offered these examples:
HOUSEHOLD ENERGY: Switching to lower-carbon energy in poorer countries would avert millions of tonnes of carbon dioxide (CO2) from biomass stoves and save people at risk from pneumonia, lung disease and lung cancer from particles and fumes.
The report gave the example of India, which suffers an estimated 400,000 premature deaths from biomass burning each year.
A 10-year program to introduce 150 million lower-emission cookers in India, either as cleaner fossil fuels or advanced biomass stoves, would cost less than 50 dollars per household to start with, an investment that would have to be renewed after five years.
Over the decade, this initiative would save 1.8 million adult lives and 240,000 children aged under five an equivalent achievement to nearly halving the national burden from cancer.
It would slash India's carbon dioxide (CO2) emissions by up to 200,000 tonnes per million population per year. In addition, levels of "black carbon" particles, methane and other dangerous compounds would fall by as much as a billion tonnes over the 10 years.
AGRICULTURE: Food and agriculture contribute between 10 and 12 percent of global greenhouse-gas emissions, while deforestation and changes in land use add another six to 17 percent.
By 2030, surging demand for meat, especially in fast-growing Asia, is expected to drive up livestock production by 85 percent compared to 2000 levels, which in turn will drive up emissions of methane and other heat-trapping gases.
But a 30-percent reduction in production in large livestock-rearing economies, coupled to technological improvements, would help meet carbon emissions targets and also pare the toll from heart disease inflicted by saturated animal fats. In Britain, 18,000 deaths could be averted in one year, according to their estimate.
TRANSPORT: Designing cities so that people can walk or cycle would benefit health more than introducing low-emission vehicles.
Modeling of London and Delhi, in scenarios that saw less motor traffic and more "active transport" in both cities, showed a fall in carbon emissions and in heart attacks, strokes and dementia.
In London, the switch would lead to an increase of 19-39 percent in road injuries, but Delhi would see a fall of 27-69 percent.
Also on Wednesday, senior clinicians announced they had set up a worldwide network, the International Climate and Health Council, to mobilize professionals' awareness of the link between ill-health and climate change.
In September, the heads of 18 doctors' associations urged world leaders to be decisive in Copenhagen, warning a weak response could have "catastrophic" consequences for international health.