More that 250,000 people a year will die from malaria, heat stress and starvation as early as 2030 unless climate change is tackled.
The World Health Organisation (WHO) says that global warming is the "defining issue for the 21st century" and has called on world leaders to strike a deal to reduce emissions and help improve human health across developing and first-world countries.
According to WHO estimates, climate change is already causing tens of thousands of deaths every year due to shifting patterns of disease, extreme weather events, including heatwaves and floods, and from the degradation of air quality, food and water supplies, and sanitation.
In 2012, WHO estimated that seven million people died from air pollution-related diseases, making it the largest single environmental health risk.
The upcoming United Nations climate change conference (COP 21), which takes place in Paris later this month, offers the world an "important opportunity" to not only reach a strong international climate agreement, but also to protect the health of current and future generations, it said.
"WHO considers the Paris treaty to be a significant public health treaty, one that has the potential to save lives worldwide," it said in a statement.
"Implementing proven interventions to reduce emissions of short-lived climate pollutants, like black carbon and methane from achieving higher vehicle emissions and efficiency standards, would be expected to save approximately 2.4 million lives a year and reduce global warming by about 0.5C by 2050.
"It is predicted that climate change will cause an additional 250,000 deaths per year from malaria, diarrhoea, heat stress and under-nutrition between 2030 and 2050. Children, women and the poor in lower income countries will be the most vulnerable and most affected, widening health gaps."
While countries have committed to reducing emissions in advance of the talks, the United Nations says they are not sufficient to limit warming to 2C, which scientists consider a tipping point.
"If countries take strong actions to address climate change, while protecting and promoting health, they will collectively bring about a planet that is not only more environmentally intact, but also has cleaner air, more abundant and safer freshwater and, as a result, healthier people." it said.
WHO has launched a set of climate change and health country profiles for 14 nations, which show that an additional seven million people in Bangladesh will be exposed to coastal flooding each year between 2070 and 2100 as sea levels rise, but this would reduce to 14,000 with strong action.
In Nigeria, some 70,000 premature deaths from outdoor air pollution could be prevented from 2030 onwards, it global emissions fall. More country profiles will be published in December and in early 2016.