Clouds form when water vapor—an invisible gas in the atmosphere—sticks to tiny floating particles, such as dust, and turns into liquid water droplets or ice crystals. In a newly published study, we show that microplastic particles can have the same effects, producing ice crystals at temperatures 5° to 10° Celsius (9° to 18° Fahrenheit) warmer than droplets without microplastics.

This suggests that microplastics in the air may affect weather and climate by producing clouds in conditions where they would not form otherwise.

We are atmospheric chemists who study how different types of particles form ice when they come into contact with liquid water. This process, which occurs constantly in the atmosphere, is called nucleation.

Clouds in the atmosphere can be made up of liquid water droplets, ice particles, or a mixture of the two. In clouds in the mid- to upper atmosphere where temperatures are between 32° and minus 36° F (0° to minus 38° C), ice crystals normally form around mineral dust particles from dry soils or biological particles, such as pollen or bacteria.

Microplastics are less than 5 millimeters wide—about the size of a pencil eraser. Some are microscopic. Scientists have found them in Antarctic deep seas, the summit of Mount Everest, and fresh Antarctic snow. Because these fragments are so small, they can be easily transported in the air.

Why it matters

Ice in clouds has important effects on weather and climate because most precipitation typically starts as ice particles.

Many cloud tops in nontropical zones around the world extend high enough into the atmosphere that cold air causes some of their moisture to freeze. Then, once ice forms, it draws water vapor from the liquid droplets around it, and the crystals grow heavy enough to fall. If ice doesn’t develop, clouds tend to evaporate rather than causing rain or snowfall.

While children learn in grade school that water freezes at 32° F (0° C), that’s not always true. Without something to nucleate onto, such as dust particles, water can be supercooled to temperatures as low as minus 36° F (minus 38° C) before it freezes.

For freezing to occur at warmer temperatures, some kind of material that won’t dissolve in water needs to be present in the droplet. This particle provides a surface where the first ice crystal can form. If microplastics are present, they could cause ice crystals to form, potentially increasing rain or snowfall.

Clouds also affect weather and climate in several ways. They reflect incoming sunlight away from Earth’s surface, which has a cooling effect, and absorb some radiation that is emitted from Earth’s surface, which has a warming effect.

The amount of sunlight reflected depends on how much liquid water vs. ice a cloud contains. If microplastics increase the presence of ice particles in clouds compared with liquid water droplets, this shifting ratio could change clouds’ effect on Earth’s energy balance.

The Earth constantly receives energy from the Sun and reflects it back into space. Clouds have both warming and cooling effects in this process.

Credit: NOAA

How we did our work

To see whether microplastic fragments could serve as nuclei for water droplets, we used four of the most prevalent types of plastics in the atmosphere: low-density polyethylene, polypropylene, polyvinyl chloride, and polyethylene terephthalate. Each was tested both in a pristine state and after exposure to ultraviolet light, ozone, and acids. All of these are present in the atmosphere and could affect the composition of the microplastics.

We suspended the microplastics in small water droplets and slowly cooled the droplets to observe when they froze. We also analyzed the plastic fragments’ surfaces to determine their molecular structure, since ice nucleation could depend on the microplastics’ surface chemistry.

For most of the plastics we studied, 50 percent of the droplets were frozen by the time they cooled to minus 8° F (minus 22° C). These results parallel those from another recent study by Canadian scientists, who also found that some types of microplastics nucleate ice at warmer temperatures than droplets without microplastics.

Exposure to ultraviolet radiation, ozone, and acids tended to decrease ice nucleation activity on the particles. This suggests that ice nucleation is sensitive to small chemical changes on the surface of microplastic particles. However, these plastics still nucleated ice, so they could still affect the amount of ice in clouds.

What still isn’t known

To understand how microplastics affect weather and climate, we need to know their concentrations at the altitudes where clouds form. We also need to understand the concentration of microplastics compared with other particles that could nucleate ice, such as mineral dust and biological particles, to see whether microplastics are present at comparable levels. These measurements would allow us to model the impact of microplastics on cloud formation.

Plastic fragments come in many sizes and compositions. In future research, we plan to work with plastics that contain additives, such as plasticizers and colorants, as well as with smaller plastic particles.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Enlarge (credit: Jason Edwards via Getty)

Earthquake scientists detected an unusual signal on monitoring stations used to detect seismic activity during September 2023. We saw it on sensors everywhere, from the Arctic to Antarctica.

We were baffled—the signal was unlike any previously recorded. Instead of the frequency-rich rumble typical of earthquakes, this was a monotonous hum, containing only a single vibration frequency. Even more puzzling was that the signal kept going for nine days.

Initially classified as a “USO”—an unidentified seismic object—the source of the signal was eventually traced back to a massive landslide in Greenland’s remote Dickson Fjord. A staggering volume of rock and ice, enough to fill 10,000 Olympic-sized swimming pools, plunged into the fjord, triggering a 200-meter-high mega-tsunami and a phenomenon known as a seiche: a wave in the icy fjord that continued to slosh back and forth, some 10,000 times over nine days.

Enlarge / View of the Las Gobas cave site. (credit: Miguel Sotomayor via Getty)

In a new study, we have sequenced DNA from a Christian community in medieval Spain that lived in artificial caves carved into a rocky outcrop.

This is one of several medieval cave communities known to have lived on the Iberian Peninsula—which includes both Portugal and Spain. Why these groups favored caves over more conventional village dwellings is a subject of longstanding debate for archaeologists. While it may be tempting to speculate about hermits or religious groups, there’s scant evidence to support such theories.

Our study, published in Science Advances, explores the possibilities, adding genetic analysis to what we know about the physical remains of people from the site’s cemetery. DNA was able to shed light on the ancestry of this community, their relationships to each other and the diseases that afflicted them.

Enlarge (credit: Corey Gaskin)

Back in 2010, Gary Wolf, then the editor of Wired magazine, delivered a TED talk in Cannes called “the quantified self.” It was about what he termed a “new fad” among tech enthusiasts. These early adopters were using gadgets to monitor everything from their physiological data to their mood and even the number of nappies their children used.

Wolf acknowledged that these people were outliers—tech geeks fascinated by data—but their behavior has since permeated mainstream culture.

From the smartwatches that track our steps and heart rate, to the fitness bands that log sleep patterns and calories burned, these gadgets are now ubiquitous. Their popularity is emblematic of a modern obsession with quantification—the idea that if something isn’t logged, it doesn’t count.

Enlarge (credit: Peter Zelei Images via Getty Images)

Extreme weather is, by definition, rare on our planet. Ferocious storms, searing heatwaves, and biting cold snaps illustrate what the climate is capable of at its worst. However, since Earth’s climate is rapidly warming, predominantly due to fossil fuel burning, the range of possible weather conditions, including extremes, is changing.

Scientists define “climate” as the distribution of possible weather events observed over a length of time, such as the range of temperatures, rainfall totals, or hours of sunshine. From this, they construct statistical measures, such as the average (or normal) temperature. Weather varies on several timescales—from seconds to decades—so the longer the period over which the climate is analyzed, the more accurately these analyses capture the infinite range of possible configurations of the atmosphere.

Typically, meteorologists and climate scientists use a 30-year period to represent the climate, which is updated every 10 years. The most recent climate period is 1991–2020. The difference between each successive 30-year climate period serves as a very literal record of climate change.

Enlarge (credit: matusgajdos17 / 500px via Getty Images)

For many people, the aroma of freshly brewed coffee is the start of a great day. But caffeine can cause headaches and jitters in others. That’s why many people reach for a decaffeinated cup instead.

I’m a chemistry professor who has taught lectures on why chemicals dissolve in some liquids but not in others. The processes of decaffeination offer great real-life examples of these chemistry concepts. Even the best decaffeination method, however, does not remove all of the caffeine—about 7 milligrams of caffeine usually remain in an 8-ounce cup.

Producers decaffeinating their coffee want to remove the caffeine while retaining all—or at least most—of the other chemical aroma and flavor compounds. Decaffeination has a rich history, and now almost all coffee producers use one of three common methods.

Enlarge / Taku Glacier is one of many that begin in the Juneau Icefield. (credit: Mauricio Handler / Getty Images)

The melting of one of North America’s largest ice fields has accelerated and could soon reach an irreversible tipping point. That’s the conclusion of new research colleagues and I have published on the Juneau Icefield, which straddles the Alaska-Canada border near the Alaskan capital of Juneau.

In the summer of 2022, I skied across the flat, smooth, and white plateau of the icefield, accompanied by other researchers, sliding in the tracks of the person in front of me under a hot sun. From that plateau, around 40 huge, interconnected glaciers descend towards the sea, with hundreds of smaller glaciers on the mountain peaks all around.

Our work, now published in Nature Communications, has shown that Juneau is an example of a climate “feedback” in action: as temperatures are rising, less and less snow is remaining through the summer (technically: the “end-of-summer snowline” is rising). This in turn leads to ice being exposed to sunshine and higher temperatures, which means more melt, less snow, and so on.

Enlarge (credit: Getty | Bettmann)

If you were to envision the kind of accident that would cause a person’s bowels to explode out of their body, you might imagine some sort of gruesome stabbing or grisly car accident. You’d probably never imagine that something as commonplace and harmless as a sneeze would cause this kind of ghastly injury—but that’s exactly what happened to a Florida man earlier this month.

The man had recently had abdominal surgery and was suffering from wound dehiscence—where his surgical scar wasn’t healing properly. While eating breakfast, the man first sneezed, then began coughing. He noticed pain and a wet sensation on his lower abdomen—only to discover several loops of his bowel had burst through his unhealed wound.

The man was rushed to hospital for emergency surgery where his bowels were returned to his abdomen.

Enlarge / Map from drone mission search for the Encephalartos Woodii in the Ngoye Forest in South Africa. (credit: CC BY-NC)

“Surely this is the most solitary organism in the world,” wrote paleontologist Richard Fortey in his book about the evolution of life.

He was talking about Encephalartos woodii (E. woodii), a plant from South Africa. E. woodii is a member of the cycad family, heavy plants with thick trunks and large stiff leaves that form a majestic crown. These resilient survivors have outlasted dinosaurs and multiple mass extinctions. Once widespread, they are today one of the most threatened species on the planet.

The only known wild E. Woodii was discovered in 1895 by the botanist John Medley Wood while he was on a botanical expedition in the Ngoye Forest in South Africa. He searched the vicinity for others, but none could be found. Over the next couple of decades, botanists removed stems and offshoots and cultivated them in gardens.