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Rising carbon dioxide (CO2) levels from burning fossil fuels have been linked to sea level changes, snowmelt, disease, heat stress, severe weather, and ocean acidification.

Yet because it does not affect respiration directly, CO2 is not considered a classic air pollutant. Noting that increasing levels of CO2 cause temperature and water vapor content to rise, Jacobson uses photochemistry to determine that these factors independently feed back to increase ground-level ozone concentrations.

This can harm lung function and irritate the respiratory system. Using a high-resolution model that correlates pollution levels to human health, the author finds that each one degree Celsius rise in temperature may increase U.S. annual air pollution deaths by about 1000.

About 40 percent of these deaths may result from elevated ground-level ozone concentrations. The rest are likely from particles, which would increase due to CO2-enhanced stability, humidity, and biogenic feedbacks.

The author notes that many of these deaths would occur in urban populations subject to smog, as are residents of some areas of California. Extrapolating U.S. deaths to global population yields about 22,000 excess deaths expected worldwide each year.

Some key points of the study were:

  • Higher temperatures due to CO2 increased the chemical rate of ozone production in urban areas.
  • CO2 also increased water vapour in urban areas, boosting temperatures even more.
  • Air temperatures rose more rapidly than did ground temperatures, which changed the vertical temperature profile and decreased pollution dispersion, concentrating pollution near where it formed.
  • Urban areas already suffering from pollution will be affected most.
Full article: Mark Z. Jacobson (Stanford University)  "On the Causal Link between Carbon Dioxide and Air Pollution Mortality."