Aerosols: a cloud on the horizon?

By Rose,
on 13 June 2022

Do you ever look at the clouds? Perhaps you notice them when you’re lying in the grass on a lazy day, looking out of your office window to distract yourself, or peering at the sky as it threatens to break open at the moment you jump on your bike? And who doesn’t enjoy a sunset even more when a red glow stretches across the sky, decorated with ribbons of white cloud? But did you know that when you’re enjoying these twilight rays, the sun has long since disappeared beyond the horizon? The blue light is filtered away, leaving the red glow behind (link in Dutch). It’s crazy when you think about it…

The clouds: they make life on earth a bit more interesting. But that’s not the only thing the sky does for us. How great is it to take a deep breath of fresh air after sitting indoors for a day?

Behind the air we need to breathe and our familiar cloudy sky hides the story of ‘aerosols’. These miniscule particles float around in our air, and they’re essential for the existence of clouds. The amount and type of aerosols in our air determine the quality of our lives. Are you feeling warm, cold or muggy? It’s the aerosols making that happen.

Small, smaller, smallest

Aerosols can come from natural sources, like salt crystals from the ocean, grains of desert sand or tiny particles released during a volcanic eruption or a forest fire. They can also be produced by human activity, such as burning fossil fuels in transportation and industry, or through agriculture and livestock. The last example in particular has a negative effect on air quality, and therefore also our public health. Most of the aerosols produced by humans are ‘ultrafine particles’ – they are so small that they can penetrate deep into our bodies. This can cause various health problems (link in Dutch), such as lung cancer, heart and circulatory diseases, and concentration issues. The European Environment Agency notes that in 2019, in Europe alone, 307,000 people died prematurely as a result of exposure to particulate matter pollution. More than half of these deaths could have been prevented if the new WHO air quality guideline values had been met. This is reason enough to add aerosols to the Stockholm Resilience Centre’s scientific nine planetary boundary model.

Direct and indirect cooling

In addition to their impact on our health, aerosols also play an important role in the warming and cooling of the earth. In our podcast ‘On a date with the planet’ (Op date met de planeet, in Dutch), Herman Russchenberg, professor of geosciences at TU Delft, distinguishes between white and black aerosols. White aerosols reflect the sun’s light and heat like mini mirrors. Black aerosols, conversely, absorb heat and hold it in the atmosphere. ‘And that puts you right at the heart of the climate problem,’ Herman said.

We don’t want the emission of ultrafine aerosols to be too high because they have proven to be detrimental to our health. But at the same time, these particles have a cooling effect on the earth, as they also form clouds. The more particles there are in the air, the more water droplets a cloud holds, and the more water droplets a cloud holds, the more sunlight it can reflect. Nature made a great infographic explaining the process by which aerosols have a direct and indirect cooling effect.

Self-healing ability

This is, of course, not a free pass to keep polluting the atmosphere. That would be the equivalent of getting drunk continuously to avoid a headache. But this contradiction does illustrate nicely how the Earth works systematically as a whole, and how all nine planetary boundaries are interconnected. There’s a lot to learn about our planet’s self-healing ability. And who knows, if we can expand that knowledge, maybe we’ll have the tools we need to make the planet habitable for us.

What can we do?

We don’t have time to wait for scientific solutions, and the way it looks now, we’ll never be able to completely solve the harmful effects of our behavior. So it’s a good idea to get started yourself! Your actions really help – in Europe, the air was demonstrably cleaner in 2019 than it was in 2018 (link in Dutch). Here are some tips for contributing to cleaner air and better health:

Would you like to better understand what aerosols are, and why it’s important to know? Then we recommend this article in De Correspondent (in Dutch). And, of course, listen to episode 2 of our podcast, if you haven’t already!

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