High Stakes: The Aerosol Case

There is little dispute that we live on a planet sensitive to and undergoing significant global change. The world is growing increasingly crowded, with a global population around 7 billion and rising. Two of the most populated parts of the world, India and China, are rapidly developing economies. Growth in population changes the health of our land, water and air resources. Scientists are hot on the trail of aerosols because the stakes to uncover their role as a climate forcing are so high, increasing the risks and consequences of future dramatic changes in the habitability of Earth.

Why the stakes are high

Aerosols may be a significant trigger for the rise in global respiratory health problems resulting from people inhaling aerosol and other pollution particulates emitted from factories, cars, power plants and even fires. In England (1952) an extreme pollution event produced by people burning coal and industrial emissions, The Great Smog, resulted in thousands of deaths. While Clean Air standards help us control pollution, aerosol pollution in industrial areas continues to cause health problems, like bronchitis and asthma, for a significant number of people. The financial and human costs of asthma can be considerable, limiting a person’s ability to work, go to school and participate in other every day activities.

Aerosols that produce a cooling effect may be masking the real extent of global warming going on today and predicted for the future. Reports that by 2035 global energy consumption is expected to increase by 53% are certain to be coupled with large increases in pollution from aerosol and other particulate sources. Complicating matters, policies to clean the environment and remove these cooling aerosols may also be unleashing the full force of the greenhouse warming gases that we have been adding to the atmosphere for more than a century. Among the scientists most eager to get precise aerosol measurements are climate modelers who make predictions for future climate. With improved aerosol data, a better GISS climate model is expected to emerge. Modelers believe we will be able to distinguish between human and natural-made aerosols in the climate models, and more precisely represent aerosol interactions with clouds and their influence on global percipatation. In the end, we will have more certainty in model predictions of climate change and our abilities to use models to inform policy decisions.

Researchers at GISS are finding that large emissions of black carbon (soot) and other pollutants can impact local weather and climate. When aerosols interact with sunlight and clouds in a region their ability to reflect and absorb light and to serve as the seeds for growth in cloud droplets can produce dangerous weather extremes, like droughts and floods. Clouds are major weather-makers. In a region like South America where there is a great deal of biomass burning to clear land for agriculture and development, researchers believe they are seeing an aerosol effect that is reducing the amount of cloud cover and precipitation which is contributing to regional droughts. Similarly, NASA scientists are seeing the effects of dust, aerosols and black carbon transported around Asia. However, in this case they find aerosols are absorbing sunlight and heating up the air to accelerate the Indian monsoon season and lengthen the rainy season. In another case, NASA researchers find evidence that climate change impacts of aerosols building up in the mid-latitudes of the Northern Hemisphere and the Arctic, "is just as strong as greenhouse gases." Their evidence shows the Arctic is especially sensitive to aerosols; where scientists report the greatest increase in temperature since 1976.