CO2 pollution from burning fossil fuels has been linked to sea level changes, snowmelt, disease, heat stress, severe weather and ocean acidification. But it hasn't been identified as the cause of significant numbers of deaths.
Noting that increasing levels of CO2 cause temperature and water vapor content to rise, Mark Jacobson and colleagues at Stanford University used photochemistry to determine if such CO2 increases also cause increases in ground-level ozone concentrations that can harm lung function.
Jacobson found each 1-degree Celsius rise in temperature can increase U.S. annual air pollution deaths by about 1,000, with approximately 40 percent of such deaths resulting from elevated ground-level ozone concentrations. The rest are likely from particles, which would increase due to CO2-enhanced stability, humidity and biogenic feedbacks, he said.
The researchers said many of the deaths would occur in urban populations subject to smog, such as some areas of California.
Extrapolating U.S. deaths to global population yields about 22,000 excess deaths expected worldwide each year.
The research is published in the journal Geophysical Research Letters.