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Monday, 8 April 2019

Bringing the Cooling Effects of Aerosols Down To Earth

Next up in what has become mini-series of "is air pollution still a big problem"...

New research shows that aerosol pollution offsets the heating effects of greenhouse gas pollution to a much more significant degree (no pun intended) than originally thought.

As aerosol particles collectively block out sunlight, they have a cooling effect. Because of this, if today we suddenly stopped all forms of air pollution, Earth's atmosphere would get even hotter.

aerosols: While "aerosol" is often used in everyday conversation to describe canned products like hairspray, it also refers to tiny particles suspended in the air.

If you are at a construction site and see dirt being stirred up, you are seeing an example of aerosols. Large amounts of aerosols from volcanic eruptions are one suspected cause of a "little ice age" in the past (Parry, 2012).

Aerosols can also pose direct threat to human health. (Marvel)


Heat-trapping greenhouse gasses remain in the atmosphere longer than aerosols which have a cooling effect. If all air pollution came to a sudden stop we would quickly lose the cooling aerosols, but not the heating greenhouse gasses so quickly. This would allow the GHGs (greenhouse gasses) to have a more full heating effect.

According to the international team of scientists who did the calculations, the difference would be about 0.5 to 1.1 degrees Celsius warmer. (Samset et al., 2018)


The report highlighted in the summary that "to keep within 1.5 or 2° of global warming, we need massive reductions of greenhouse gas emissions. At the same time, aerosol emissions will be strongly reduced.... This means that it does not only matter whether or not we reach international climate targets. It also matters how we get there."

The report also mentions that the Northern hemisphere is especially sensitive to aerosol removal because of the location they are being emitted from. Also, more precipitation could be expected in places making significant reductions, as aerosols have a drying effect.

In an interview with Yale Environment 360, Bjorn H. Samset, lead author of the report made clear that he does not want the findings to be taken as encouragement to go ahead with intentionally spraying more aerosols into the atmosphere, likening its uncertain consequences to Russian Roulette. (Schiffman, 2018)

Bringing it Down to Earth

"This means that it does not only matter whether or not we reach international climate targets. It also matters how we get there." (Samset et al., 2018)

The headlines surrounding the findings may be surprising, but the average North American carbon footprint is way beyond having to reconsider reducing pollution. The evidence still points to greenhouse gases as a serious problem, and aerosols themselves pose their own threat to human health. (Marvel)

However, this information can help illustrate the different benefits between making needed cutbacks in consumption, and actively increasing carbon sinks.

carbon sink: Natural systems that absorb carbon dioxide. This includes trees and other plants, oceans, and soil. (Thompson, 2012)

carbon sequestration: The process of capturing and storing carbon dioxide, namely from the atmosphere. (USGS). This term often references natural processes, but can also refer to artificial ones.

ecological footprint: A metric used to illustrate how much biologically productive land is needed to support a person or group's lifestyle or consumption. (Global Footprint Network, 2018) Carbon footprint is the amount of that land is needed to sequester the resulting carbon emissions, though it can alternatively refer to tonnes of carbon dioxide emitted as a result.

These findings give a pat on the back to the benefits of conservation and increasing green space. Many innovative and handy products are making reusing and making cutbacks more convenient, but activities like increasing green spaces and enhancing carbon sequestration holds special value in their own right.

So what are some ways to help conserve, expand, and enhance green spaces?

Physically planting trees and other plants is one way, as well as supporting conservation initiatives locally and globally through organizations like WWF. Also, reducing or eliminating meat consumption reduces the amount of land space required to grow foods that are used to feed livestock.

In the end, when it comes to cutting our CO2 and making sure there are lots of trees, both are needed (PIK Press), and there are many things we can do to improve in to both "cutting the carbon", and actively increase its sequestration.


Global Footprint Network. (2018, December). Climate change and the Ecological Footprint and carbon footprint. Retrieved April 8, 2019, from

Marvel, K. (n.d.). Ask The New York Times. Retrieved April 2, 2019, from

Parry, W. (2012, January 30). Volcanoes May Have Sparked Little Ice Age. Retrieved April 1, 2019, from

PIK Press. (2017, May 18). Climate stabilization: Planting trees cannot replace cutting CO2 emissions. Retrieved April 8, 2019, from

Samset, B. H., Sand, M., Smith, C. J., Bauer, S. E., Forster, P. M., Fuglestvedt, J. S., . . . Schleussner, C. (2018, January 24). Climate Impacts From a Removal of Anthropogenic Aerosol Emissions. Retrieved March 3, 2019, from

Schiffman, R. (2018, March 8). How Air Pollution Has Put a Brake on Global Warming. Retrieved March 3, 2019, from

Thompson, A. (2012, December 21). What is a Carbon Sink? Retrieved April 1, 2019, from

USGS. (n.d.). What is carbon sequestration? Retrieved from

Title Edited January 2020

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