Air pollution kill an extra 260,000 by the end of the century if climate change goes untackled, a study warned.
Global warming will alter the concentrations of air pollutants causing the premature deaths of 60,000 by 2030 and 260,000 deaths by 2100.
The smog will affect all regions except Africa.
This is on top of the millions globally who die from the effects of smog from traffic, factories, power stations and dust.
Scientists warn higher temperatures will speed up the chemical reactions that create air pollutants like ozone and fine particulate matter, which affect health.
And as droughts and drier regions spread, pollution will be worse because the rain will not wash the pollutants out while there is a heightened risk of wildfires and dust from erosion.
As trees respond to higher temperatures, they will also emit more organic pollutants.
The rise in toxic air pollution adds to other risk of death from climate change including heat stress, a lack of clean water and food, severe storms and the spread of infectious diseases.
The University of North Carolina at Chapel Hill study adds to growing evidence that the overall health effects of a changing climate are likely to be overwhelmingly negative.
It was also the most comprehensive study yet on how climate change will effect health via air pollution, since it makes use of results from several of the world’s top climate change modelling groups.
Associate Professor Dr Jason West said: “As climate change affects air pollutant concentrations, it can have a significant impact on health worldwide, adding to the millions of people who die from air pollution each year.”
The study used an ensemble of several global climate models to determine the number of premature deaths that would occur due to ozone and particulate matter in 2030 and 2100.
For each model, the team from in the UNC Gillings School of Global Public Health assessed the projected changes in ground-level air pollution that could be attributed to future climate change.
They then overlaid these changes spatially on the global population, accounting for both population growth and expected changes in susceptibility to air pollution.
Climate change is expected to increase air pollution-related deaths globally and in all world regions except for Africa.
Specifically, five out of eight models predicted there will be more premature deaths in 2030, and seven of nine models in 2100.
The associate professor of environmental sciences and engineering said: “Our finding that most models show a likely increase in deaths is the clearest signal yet that climate change will be detrimental to air quality and health
“We also collaborated with some of the world’s top climate modeling groups in the United States, United Kingdom, France, Japan and New Zealand, making this study the most comprehensive yet on the issue.”
The study was published in the journal Nature Climate Change.