The Surprising Ways We’ve Altered Earth’s Atmosphere… For the Worse

Uncovering the Invisible Changes in Air Quality and Climate Triggered by Our Modern World

My biology professor in Middle School taught us the principles of natural and artificial selection. Then, he told us about an unintentional example of artificial selection. A black form of the peppered moth took over the industrial parts of the UK during the 1800s.

This moth species used to live in light-colored tree bark, so being white helped them camouflage from predators. From time to time, a black moth was born, but it tended to leave fewer offspring because birds could spot it more easily.

However, as pollution turned the bark on these trees black, these unfortunate varieties gained a camouflage advantage. Soon, the majority of the moth population was black.

This story blew my mind. We have been changing whole populations of animals since the onset of the Industrial Revolution and even earlier through overhunting.

Despite that, people like to debate that human civilization isn’t “so bad” for the environment and that climate isn’t going to bite back. Unfortunately, the impact of human activities on the environment is becoming increasingly clear. Things are changing way faster than we’d like to.

One of the lesser-known but important areas of study is how our actions have altered the composition of aerosols in the atmosphere, particularly secondary organic aerosols (SOAs). But first, what are SOAs?

Secondary Organic Aerosols (SOAs) are tiny particles that float in the air and can affect both the environment and our health. These particles form when certain gases released by plants, cars, factories, and other sources mix with chemicals already present in the atmosphere. The result is a kind of pollution that isn’t directly emitted but forms through these chemical reactions in the air. In a way, pollution that it’s cooked in the air.

Why are these important, though? Well, SOAs are important because they can influence how much sunlight reaches the Earth and how clouds form, which, you guessed it, can impact our climate.

On top of that, they also contribute to air pollution, specifically to the fine particles in the air (known as PM2.5) that we sometimes hear about in air quality reports (check your phone to see a report on air quality, that’s one way they measure it). These fine particles can be harmful to our health, especially for people with respiratory or heart conditions like my asthmatic wife.

In simpler terms, SOAs are a part of the invisible pollution that we can’t see, but which plays a big role in the quality of the air we breathe and the overall climate. So, understanding and controlling SOAs is crucial for keeping our air clean and protecting our health.

The thing then is that SOAs have evolved from the preindustrial era to the present day. A recent study led by the Institute of Atmospheric Physics at the Chinese Academy of Sciences offers new insights into this transformation, highlighting the significant changes in SOA levels over time.

This is where the story gets interesting. The researchers employed a sophisticated approach to explore how SOA levels have changed, integrating various advanced tools into their models. They used the Model of Emissions of Gases and Aerosols from Nature (MEGAN) from the European Union coupled with the Aerosol and Atmospheric Chemistry Model (IAP-AACM) to calculate the emissions of biogenic volatile organic compounds (VOCs), which are crucial precursors to SOAs.

The study also utilized a dynamic global vegetation model (IAP-DGVM) to simulate historical vegetation patterns, which provided a more accurate estimate of natural emissions in the preindustrial period (see figures for reference). The researchers were able to simulate SOA formation from nontraditional pathways, including the aging of primary organic aerosols and the oxidation of intermediate VOCs.

What did the authors find? One of the study’s standout findings is the shift in SOA sources from the preindustrial period to the present day. As you can imagine, in the past, biogenic SOAs — those formed from natural emissions — dominated the atmosphere. However, the research revealed that human-made SOAs have surged since the Industrial Revolution.

In fact, anthropogenic SOAs now account for up to 53% of total SOA levels, a significant increase compared to preindustrial times.

“In the preindustrial period, natural sources were the primary contributors to SOA. However, our findings show that human activities have greatly amplified SOA production in the present day, leading to significant changes in global air quality,” explained Dr. Chen Xueshun, one of the study’s corresponding authors. As showcased by the author, this highlights the extent to which human activities have reshaped the natural balance of aerosols in the atmosphere.

As I explained before, the increase in anthropogenic SOAs has important consequences for our environment. These aerosols not only affect air quality by contributing to pollution but also influence climate by interacting with sunlight and clouds. Everything is being altered.

The study also found something unexpected: the response of biogenic SOAs to changes in anthropogenic emissions is more sensitive now than it was in the past. This means that human activities are not only adding more aerosols to the atmosphere but are also amplifying the effects of natural aerosols. Their harmful effects are being magnified.

So, what does all of this mean to us?

This research reminds us of the far-reaching impact of human activities on our planet’s atmosphere. The unprecedented increase in anthropogenic SOAs since the Industrial Revolution highlights the need for better air quality management and more effective climate policies. After all, understanding the sources and formation processes of SOAs is key to mitigating their negative effects and protecting both human health and the environment.

I hate hearing more and more stories of how we are changing biological species with our actions. Something needs to be done, or we’ll soon have a world we can no longer recognize. Will our grandchildren only know it through photos? Will they be able to breath clean air while doing it?