NASA's Curious Universe - Tiny but Mighty

Episode Date: November 28, 2023

What do air pollution, thunder clouds and climate change have in common? Aerosols! These tiny particles, generated by everything from desert dust storms to car exhaust, play a huge role in our atmosphere, affecting our health when we breathe them in and even changing the weather. Globally, they play an even bigger role, changing how much sunlight gets through to Earth’s surface and heating or cooling our entire planet. Through new satellite missions, NASA atmospheric scientists like Kirk Knobelspiesse and public health experts like Susan Anenberg are working together to untangle aerosol mysteries. NASA's Curious Universe is an official NASA podcast. Discover more adventures with NASA astronauts, engineers, scientists, and other experts at nasa.gov/curiousuniverse

Thank you for listening to NASA's curious universe. If you're new to the show and excited to learn more about the universe around us, welcome. You're in the right place. We're hard at work making new episodes, but we just wanted to stop for a minute and say, thank you. We're very happy to have you here. And we have some good news for you. We have over 50 episodes exploring all sorts of fun topics from human spaceflight to astrophysics and more. Whether you're a total space nerd or a first-time space explorer, I'm telling you, there is a curious.

Universe episode for you. So find your favorite episode at nasset.gov slash curious universe or wherever you listen to podcasts. So glad you found us. Thanks and enjoy the show. Have you ever sat by a crackling campfire and lean back to watch the gray sooty smoke rise up into the night sky? Then maybe the wind shifted a bit and it headed toward you making you cough and scoot your chairway. Have you ever wondered exactly what was in that smoke? It turns out, smoke is made up of gases and these teeny tiny particles called aerosols. So aerosol is sort of a blanket term to refer to particulate matter that suspended in the atmosphere. So your campfire produces aerosol pollution on a small scale, enough to make you a little uncomfortable. Now, think about what a raging wildfire would generate.

A lot of what's emitted from a fire is particles or gases that turn into particles. We think about bad air quality days, downwind from a big smoke event or something like that. Those are aerosols. That's Kirk Noblespeze. He's an atmospheric scientist at NASA, and his lab studies aerosols. Another way of saying it might be that we observe microscopic phenomena from space. Smoke from your campfire or from a raging wildfire. isn't the only place you'll find aerosols.

These microscopic particles floating around the atmosphere have a lot of sources down here on the ground, both natural and man-made. There's types of aerosols that are created as byproducts of human emissions from vehicle emissions or for industrial emissions. There's other types of aerosols that are naturally generated by, say, wind on the surface of the ocean.

So sea salt, sea breeze, and that's a type of aerosol as well. When you hear the word aerosols, you might also think of spray cans. The little liquid particles they spray out, like hairspray or paint, are also aerosols. Wherever aerosols originally come from, your car's tailpipe, a forest fire, or the salty sea, they don't stay put. Once they rise high into the air, they can cross oceans and continents with ease and affect the whole world. So for example, dust blowing off of a desert is one example of an aerosol.

And you can look at a place like the Saharan desert, and the dust that's produced there gets blown out over the oceans. And it makes it as far as, say, the Amazon basin. Aerosols are everywhere, and they affect our life on Earth in ways that can be hard to wrap your head around. This is NASA's curious universe. Our universe is a wild and wonderful place. I'm your host for today, Jacob Pinner, and in this podcast, NASA is your tour guide. Aerosols may be tiny, but they play a huge role in our atmosphere,

affecting our health when we breathe them in, and even changing the weather, how clouds form and when and where it rains. Globally, they play an even bigger role, changing how much sunlight gets through to Earth's surface and heating or cooling our entire planet. In this episode, we'll learn why these tiny bits of dust, salt, ash, and smoke are so important to our life on Earth. Meet the NASA scientists who've dedicated their lives to studying them and explore all the things we still don't know about how they

impact the world around us. Aerosols are small. How small? Well, in science, we use a unit called the micron to measure very small things. A single one of the hairs on your head is about 70 microns wide. Most aerosols are between 1 and 10 microns in diameter. So you can't see them with your eyes. But it turns out it's actually pretty easy to see them from space. And it all starts with light. So when sunlight hits the Earth, we can think of, you know, many, many, many little waves of sunlight that come into our atmosphere and they start interacting with things. Those rays of sunlight start bumping into gases and other components of our atmosphere.

Things like aerosols. An interesting aspect of aerosols is that they're almost the same size as a wavelength of light. And that means the optics of how these aerosols reflect and absorb sunlight is very complicated. So for example, imagine you have a bunch of smoke, take a picture of it from space. Well, you can't see the surface anymore. That's because the smoke is reflecting light or it's absorbing light, and it's through that interaction with light that we're able to understand what's there. Aerosols are so small that when we look for them from space,

what we're really looking for is the light they reflect away. We can't see them directly. Some scientists also collect air samples on the ground, which they can analyze to learn the amount of aerosols in them. But you can't do that over the entire. entire world all at once. For that kind of view, you need satellites. Way back in the 1950s and 60s, scientists measuring air quality on the ground, and public health

researchers studying human health impacts, started sounding the alarm on air pollution. Air pollution has become a worldwide preoccupation. The foul air that had come to be accepted as an inevitable part of city living has suddenly become intolerable. America was once on a path toward environmental self-destruction. The Industrial Revolution left dirty air and serious human health problems in its wake. Americans took to the streets to protest and convinced Congress, we had an air pollution problem. The U.S. passed the Clean Air Act in 1970, and in many ways, things have improved a lot since then.

Since 1970, EPA researchers have investigated dangerous air pollution. pollutants and provided the scientific foundation for regulations and solutions to reduce them. In fact, air quality has gotten so much better, we can see the difference from space, using more than 20 years of observations from NASA satellites, particularly one called ORA. But unfortunately, there are still problems today. Especially in polluted cities, the air is full of aerosols called PM2.5. fine particulate matter less than two and a half microns wide. Since these aerosols are so small, they can do a lot of damage to our bodies.

So what happens when you're walking through, say, a cloud of wildfire smoke, or you're walking along a busy roadway that has a lot of truck traffic and you see these sort of clouds of darker smoke? What happens when we breathe that in? My name is Susan Annenberg. I am professor and chair of environmental and occupational health at the George Washington University. I have had the experience, maybe some of you have as well, I've had the experience of living in a more polluted location or visiting a more polluted location and blowing my nose and seeing a little bit of black and brown stuff come onto the tissue. That's the pollution that you're breathing in. I'm sorry to be the bearer of bad news, but the air that you are breathing right now, the air that all of us are breathing right now contains a multitude of chemicals,

particles, and gases. And we're breathing that in on a daily basis. Once you breathe in those tiny particles from a cloud of smoke or a truck exhaust pipe, they can work their way deep into the branches of your lungs. And those particles are actually so small that they can get into the bloodstream. once they get into the bloodstream, then they can affect every organ of the body. Over the long term, the way that your body reacts can manifest into more serious diseases. So we actually see more heart attacks, stroke, asthma, chronic obstructive pulmonary disease

for people who have been exposed over the long term to high levels of air pollution. As a public health expert, Susan also works on NASA's health and air quality Applied Sciences team, or Haycast. Her job there is to translate the air quality data NASA records from space for public health agencies on the ground. Then they can use that data to better protect their community members. So she has a good sense of how bad the problem is. Scientists have found that nearly everyone on the face of the planet is exposed to unhealthy

levels of air pollution. More than 95% of the human population is breathing air that exceeds world health organization guidelines for clean air. It's been estimated that there's about 7 million premature deaths each year due to unhealthy air pollution. Air pollution is a global problem. But that doesn't mean aerosols are distributed equally across the world. Using NASA satellite data, Susan can see where pollution is well. worse. And everywhere she looks, she tends to see some patterns. When we look within individual cities, we see that there's neighborhood scale differences in those particle levels. By comparing

the satellite data with data from doctors on health outcomes, she can see that people who live near industrial areas tend to have worse health effects because they're breathing in more aerosols. Overall, pollution is getting better, especially in cities. But with climate change, there can be surprises. You might remember that in the summer of 2023, smoke from wildfires in Canada traveled across the United States, darkening the skies across the country. Like in previous decades, you could see the dark clouds of air pollution from space. As our Earth warms, wildfires are becoming more intense and frequent, which means more aerosols in the atmosphere. These changing aerosol concentrations have far-reaching and complicated effects even beyond human health.

Take clouds, for example. Here's Kirk again. If we lived on a planet without any aerosols, the distribution of clouds on this planet would be very different. And that's because cloud droplets just don't spontaneously form. Okay, I'm going to take you back to elementary school science for a minute here. So, class, take a seat, sharpen your pencils, please. Do you know where clouds come from? You probably learned that they form when enough water vapor condenses in the atmosphere.

The sun beats down on liquid water on the ground, and that energy in the solar radiation excites the water molecules, turning them into a gas. That's called evaporation. Warm air brings the water high into the atmosphere. Then little water droplets form as the water cools and condenses back into a liquid in the atmosphere. Finally, clouds grow bigger and heavier until they let the water go, in rain or other forms of precipitation. Now, that's all true, but there's another detail you might not have learned about.

Aerosols play a critical role in the process. Without them, most clouds wouldn't form. water when it condenses, likes to form onto something. And so if you have aerosols in an area, cloud droplets like to form around aerosols. In other ways, they're sort of like the nuclei, the seed, around which many cloud droplets form. So if you change the types of aerosols in an environment, you change the types of clouds are there. You change things like, you know, is that cloud made up of a small number of really big droplets

or a large number of very small droplets? You know, same amount of water, just dispersed in different ways. So that can affect how long a cloud lasts, when it turns into rain, that sort of thing. Clouds are complicated. So complicated, scientists still don't fully understand them, or how aerosols affect them. So there's different processes in the formation and lifetime of a cloud. Aerosols interfere with that whole process. Imagine a place without much air pollution.

Maybe the middle of the ocean, far away from any continent. Now, there are some aerosols in the air here. If there weren't any, it would be impossible for clouds to form. But the comparatively few aerosols present are natural ones, particles of sea salt. That affects the kinds of clouds that can form. Since it's difficult for those droplets to form without something to form upon, you'll have a small number of particles that form,

and then the other water will just kind of condense on that. So you'll form a cloud that has a small number of very large droplets. Another thing, and maybe this is obvious, you know, the larger the cloud droplets are, the faster they fall out of the cloud, the quicker they turn into rain. Now, let's lead the open ocean behind and make our way to a port near a big coastal city, polluted by cars and trucks and cargo ships with tons of aerosols in the air for water to condense around. Man-made aerosols tend to be smaller and more numerous than natural ones. So now you have the same amount of water.

But it's spread among many, many small particles throughout the cloud, or small droplets throughout the cloud. That means air pollution can impact rainfall amounts because the individual droplets are smaller, lighter, and less likely to fall. But in some cases, when enough small droplets accumulate into a specific type of huge convective cloud, it can cause powerful thunderstorms. This is an active area of research. and scientists are still far from figuring out the complex ways clouds and aerosols interact. But a few things are clear. Day-to-day, by delaying or provoking rain and changing how clouds form, aerosols can change weather patterns.

And over the long term, they can change our climate, too. How? That's after a short break. Hey, Curious Universe listeners. Do you want even more great storytelling, live launch coverage, and behind-the-scenes access into the world's premier space agency? Well, let me tell you about NASA Plus. NASA Plus is NASA's new on-demand streaming service. Out now on all major platforms.

Get ready to travel through space from the comfort of your own home. The best part? It's family-friendly. There's no subscription required and it costs nothing. Check out Other Worlds, a documentary series that follows scientists as they explore planets in our solar system and beyond with the James Webb Space Telescope.

or the new season of NASA Explorers, which takes you behind the scenes of the Osiris Rex mission to collect an asteroid sample and bring it back to Earth. You can download the NASA app on your phone, stream on Roku and Apple TV, or visit us online at plus.nassah.gov. See you there. Okay, you might have heard of the greenhouse effect.

When we burn fossil fuels like oil and coal, to run our cars or generate electricity and power plant, greenhouse gases like carbon dioxide and methane fill our atmosphere and trap energy from the sun, preventing it from escaping into space. That warms up our world. But there's another side of the equation, which is how the energy gets to the surface of the Earth in the first place. It turns out, aerosols play a big role on that side of the equation. The side we don't talk about much.

How can tiny aerosols have such a big effect, changing our global climate? Kirk thinks the best way to explain it is through an example, cargo ships. According to a recent NASA study, it turns out cleaning up cargo ship emissions has had a complicated effect on our climate that scientists are just beginning to understand, an effect that shows just how powerful aerosols can be. I'll give an example. So if one looks for a long time at satellite images of the oceans, You'll look at cloud decks that form regularly over the oceans in many parts of the world,

and you'll see these streaks through them. And these streaks will be aligned with where ships have gone. They're called ship tracks. Every day, tens of thousands of cargo ships crisscross the world's oceans, emitting aerosol pollution from their smokestacks as they burn dirty oil to power their massive engines. Remember, normally the atmosphere over the open ocean contains fewer air. aerosols compared to places like cities. So those aerosols are being put into an environment which is otherwise very pristine in terms of aerosols.

The only other types of aerosols from there would be, say, sea salt aerosols. And so the presence of those aerosols changes the types of clouds in an area. So in some cases they create clouds and they look like contrails in a way, like from airplanes. And that's a similar phenomenon. Remember how scientists detect aerosols in our atmosphere from space? They look for how much sunlight those aerosols are reflecting. Clouds are made of aerosols and water droplets, so they also reflect light. But not all clouds are created equal.

Well, a cloud made of lots of small droplets tends to reflect a lot of light. They tend to be very bright clouds. And so that's one of the things that reflects energy back out to space again and keeps it from being absorbed by the earth. The more droplets, the more surfaces for light to reflect off of. Those ship track clouds Kirk was talking about form when water droplets condense around the tiniest of aerosols. The man-made ones, ships emit. By forming these really bright, reflective clouds, aerosols play a role in shielding our planet from the sun's warming energy, reflecting solar radiation back into space.

If you have lots of clouds, you reflect a lot of energy back to space. If you have ships, if you have humans doing something to change what those clouds are like, then you also change some part of the equation that drives energy on Earth. You know, if you tally up all the sources of contributions to climate change, there's the biggies, there's carbon dioxide and there's methane, there's the greenhouse gases that are warming the planet. But there's a lot of other things that we're changing as well. And aerosols are one thing that can counteract,

at least globally in a global average sense, can counteract some of the warming of greenhouse gases. In 2020, the International Maritime Organization shifted the balance of that climate change equation. And we're still trying to figure out how the math adds up. But recently, there's been changes to regulations on sulfur emissions from ships. Previously, there were not a lot of regulations on what is emitted from ships at sea. Now there are. Ships have had to clean up their acts by 80%.

With fewer aerosols emitted by those ships, scientists are watching those ships. scientists are watching those shiptrack clouds disappear from space. When you don't generate those sorts of clouds, the overall reflectance of the earth is a little bit less. You know, there's less bright things of the surface of the earth. That's relevant to climate. And so that's good for us as humans to breathe. But there is some evidence that that also means that aerosols are not blocking as much sunlight as I used to. and that has in some ways contributed to the warming of the earth.

Fewer aerosols in ship pollution have meant fewer shiptrack clouds over maritime shipping corridors across the oceans. Now more sunlight can reach the dark ocean water in those places, which could potentially have a warming effect. It's like wearing a black t-shirt on a hot summer day instead of a white one. Well, it is a bit more complicated than that. Thick cloud cover can also absorb and trap heat that would have otherwise escaped into space. Scientists are far from fully understanding the role aerosols play in climate change.

And this ship track example shows just how much more there's left to learn. And it's trying to understand these sort of complicated relationships. There's a lot of things that are involved that make it difficult for us to properly include this in climate models without better information about what's happening on the planet of the Earth. Right now, aerosols are one of the biggest question marks in scientists' efforts to model what our future climate will look like. Scientists think those reflective particles may have masked about half the warming we've caused by burning fossil fuels since the 1880s.

But it's hard to calculate exactly. And so a lot of what NASA is doing now is trying to get that better information so that we can make better predictions of climate. To do that, NASA is launching new satellite instruments that are much better at detecting aerosols than the ones we used to use. One mission called tropospheric emissions Monitoring of Pollution, or Tempo, for short, launched this spring.

For Susan, it will completely change how she tracks air pollution in cities. I'm really excited about tempo. The tempo instrument is on a geostationary satellite that hovers in place as the Earth spins beneath it. And what that means is that instead of taking one snapshot of the Earth's air per day,

like the current satellites that are polar orbiting, this satellite is going to be able to take snapshots on an hourly basis over the United States during the daylight. Since Tempo is taking images much more often than previous satellites, it'll be able to track changes in aerosols throughout the day.

So you can imagine during morning rush hour and evening rush hour were emitting a lot more pollution from cars than we are in the middle of the day. Previous satellites haven't been able to detect those kinds of changes. Tempo's more frequent images also mean better chances of directly seeing all the aerosol pollution hanging in the air above cities.

Another important satellite is called PACE, short for the Plankton, aerosol, cloud, and ocean ecosystem mission. It'll focus more broadly on aerosols across the world after it launches in early 2024. Kirk is part of the Pace mission team. Now, I'm a scientist. I'm involved with the data that will be produced by Pace. We've been involved in the design of the instrument and monitoring throughout it, but really our job starts once we start getting data. Pace has some special instruments that will allow Kirk and his fellow scientists to peer inside of clouds like never before.

If scientists understand clouds better, they'll also be able to figure out the role those clouds are playing in our climate. I do hope that with these observations we will move to a place where the role of aerosols and aerosol clouds in climate models is no longer the highest source of uncertainty. And it's something that we can more confidently predict in the future. Right now, as this episode airs, In November 2023, Pace is on its way to Florida, where it'll be packaged on top of a rocket to launch into orbit next year. Once we have the launch, we're going to suddenly have very large amounts of data coming at us from space all the time, and we need to process lots and lots of data.

My laboratory is mostly people who have sort of a computer science or programming background, and we have a lot of big computers, and we have algorithms that we've created. to process all of this data. And we need to verify that what we're doing is correct. To make sure Pace is seeing aerosols correctly, Kirk will have to do something called ground-truthing, traveling all over the land and sea to take measurements from Earth's surface, and make sure they match up with what Pace is seeing from space.

Groundtruthing for tempo is also really important. To make sure its pollution readings match up with the reality on the ground in cities. Satellites are observing the amount of pollution in a column of air, if you can envision a column of air extending up from the surface of the planet up to where the satellite is orbiting. That's what satellites are tracking. But that's not what people are breathing on the ground. People are breathing air pollution at the nose level. And so we need to really understand is the column of air that the satellite's, that the satellite is, is observing is the amount of pollution in that column of air consistent with the amount of pollution

at the air at the nose level. And that's why it's really important for us to be taking measurements at the ground level as well. Since Tempo has a bit of a head start, its ground truiting campaign is already underway. Earlier this summer, NASA flew planes low over the city of Chicago and Lake Michigan, collecting air samples to make sure Tempo's measurements from space are accurate. Today's a really exciting day for both NASA and NOAA. Today, the Tempo satellite started its first scans of North America. And we've got three aircraft in the air flying over Chicago.

Even more aerosol-spotting satellites are planned for the coming decades through NASA's atmospheric observing system. Okay, we're out of our forested area now, back over farmland. But in the meantime, tempo and pace will work together to keep an eye on our cities and seas and hopefully start to answer scientists' big open questions. Like, how do aerosols affect when and where thunderstorms form? And how big of a role are they playing in counteracting global warming? Will these satellites let us figure out how our planet's atmosphere works once and for all?

I'm not sure I would use the word figuring out for a lot of scientific endeavors because that involves that we've learned everything that we need to know. What we're doing is trying to understand better. There is so much that is unknown about this planet. I do not anticipate us knowing everything that we need to know. We are also doing a big science experiment on our planet right now by altering what it is. So there can be a lot of effort in trying to understand what's going on, and that's going to keep changing. There aren't many planets in the universe as complicated as our life-giving Earth. But we can count on NASA scientists like Kirk and partners like Susan to keep working to better understand our changing home.

And by building on decades of NASA Earth missions, tempo and pace are giving them their best shot yet. This is NASA's Curious Universe. This episode was written and produced by Christian Elliott. Our executive producer is Katie Connance. The Curious Universe team includes me, Jacob Pinner, Maddie Olson, Michaela Sosby, and of course, Patty Boyd. Christopher Kim is our show artist. Our theme song was composed by Matt Russo and Andrew Santigwita of System Sounds.

Special thanks to Katie Jepson, Michael Carlowicks, Leslie Ott, and Tianla Uwan, a NASA scientist and author of System. of the ShipTracks research we talked about in this episode. If you enjoyed this episode of NASA's Curious Universe, please let us know by leaving us a review and sharing the show with the friend. And remember, you can follow NASA's Curious Universe in your favorite podcast app to get a notification each time we post a new episode. Hey, Curious Universe listeners.

This season, we want to know what you're curious about. Send us your questions at NASA-curious Universe at mail.nassah.gov, and we'll try to track down the answer. Jacob, I have a question for you. If you could go to space, would you do it? Yeah, I don't think that's something you can say no to. I would definitely do it. But it's important to know yourself and know your limits, right?

And I know that the whole launch, lift-off process would be very, very scary for me personally. So it's a little bit like when you're a little kid and your parents make you eat Brussels sprouts or something that you don't like. And you just hold your nose, you eat them, and you know that there's going to be dessert waiting for you on the other side. that would be me through the whole liftoff process because I know that once I got to space, once I could see Earth from space and see everything else, I know it would be worth it. Totally.