Around the world, air pollution deaths each year induced by additional carbon dioxide could amount to 21,600 per degree of temperature rise. That’s a greater number than is likely to be caused by man-made, climate change-related storminess.
This is the first time that a link has been made between carbon dioxide levels and deaths from air pollution. Heightened levels of carbon dioxide raise atmospheric temperatures and water vapour content, in turn increasing ozone and particle concentrations. The ozone increases in particular occur in locations where ozone is already high, says Jacobson.
"More than 30% of these deaths occur in California, which has six of the 10 most polluted cities in the US," Jacobson told environmentalresearchweb. "This is significant since the EPA (Environmenal Protection Agency) recently denied California a waiver [to its ruling against states setting specific emission standards for carbon dioxide] based in part on (a) no special circumstances occurring in California, (b) no studies isolated carbon dioxide's effect on air pollution, and (c) no studies quantifying the health effects of carbon dioxide. This study addresses all three issues."
Jacobson says that the deaths are already occurring, since global temperatures, on average, are about 0.8°Celsius higher than in pre-industrial times.
"Based on the results of this study, I would think the EPA should revisit its decision since California does have a special circumstance based on the scientific results found here, namely that climate change will worsen air pollution the most in areas already polluted," he said.
Around 40% of the extra deaths are likely to be caused by higher ozone levels, which can cause respiratory and cardiovascular illnesses, with the rest accounted for by increased particle concentrations. Higher carbon dioxide levels ‐ and the associated increases in water vapour and temperature – can enhance the stability of particles, raise biogenic particle mass and enable particles to interact with airborne chemicals, increasing their toxicity. The study also found that cancers may increase by 20–30 for every one degree rise in temperature caused by carbon dioxide.
To obtain his results, Jacobson used the nested global-urban climate-air pollution 3D model GATOR-GCMOM. This incorporates emission, aerosol, cloud, meteorological, radiative, transport and surface processes as well as gas chemistry. Jacobson, who reported his work in Geophysical Research Letters, ran two global simulations, setting carbon dioxide levels to pre-industrial values in one of them and comparing the results.