The airborne particulates that represent the greatest danger to health, longevity and quality of life for people are also powerful enough to change our climate.
Particulate matter as small as 2.5 microns or less in diameter can alter long-established weather patterns. “Although microscopically tiny, aerosol particles can have mighty impacts on the atmosphere and climate,” writes science journalist Anuradha Varanasi for Columbia University’s Climate School. “Major volcanic eruptions and their resulting aerosol emissions high up in the atmosphere are infamous for altering monsoon circulations and precipitation patterns around the world, even triggering severe droughts in Eastern China and India.”
The most dangerous particles originate from manmade sources. “The majority of anthropogenic aerosols are made in the atmosphere from gas molecules,” explains Varanasi. “For example, during the coal burning process, the sulfur present in coal becomes oxidized and gets released into the atmosphere as sulfur dioxide gas. The gas then reacts with clouds, water vapor, and other pre-existing compounds before it transforms into sulfate aerosols that have a cooling effect on the lower atmosphere.”
For many decades sulfate aerosols were having a cooling effect on the planet. Now that many developed countries have reduced emissions of these particulates, the cleaner air has led to greater warming. Warming has, in turn, increased the amount of ozone pollution in many regions, especially in China.
“Warmer temperatures ramp up reactions between nitrogen oxides and volatile organic compounds that get trapped in the lower atmosphere,” she writes. “Researchers observed that getting rid of aerosols or fine particulate matter is another reason why Chinese cities are experiencing a spike in ozone pollution.”
Varanasi points out that a volcanic eruption by Mount Pinatubo in the Philippines in 1991 lowered global temperatures by up to a half degree Celsius for the next two years. More than15 to 20 million tons of noxious sulfur dioxide gas were released into the stratosphere, forming mists of tiny sulfate aerosols.
Meanwhile, research by scientists at the Singapore Centre for Environmental Life Sciences Engineering at Nanyang Technological University suggests the study of airborne microorganisms will help societies adjust to climate change, avoiding some of the more serious outcomes to human health and the food supply predicted by global warming models.
The study was published earlier this year in the Proceedings of the National Academy of Sciences. The research team used aircraft and a ground-based observation tower to measure microorganisms up to 3,500 meters from the Earth’s surface, and subsequently analyzed how fungi and bacteria grow, change, interact and move through the lower atmosphere.
According to a review of the findings by Science Daily, the scientists discovered that “temperature was the single most important factor influencing the composition of airborne microbial communities. As the temperature of the air changes, the species found and the ratio of bacteria to fungi change significantly. These findings suggest that the currently observed increase in global temperature will have an impact on the atmospheric microbial ecosystem, as well as planetary terrestrial and aquatic ecosystems.”
Team scientist Stephan C. Schuster explains the consequences: “If the composition of the air microbiome changes globally, it may affect human health, exacerbating respiratory syndromes in susceptible patients, or it could affect the yield of agricultural crops, which then threatens our food security. Natural processes that have worked for thousands of years such as carbon cycling on this planet may also be changed.”
Air Quality and Climate: A Toxic Correlation
