A new study from the Department of Meteorology and Geophysics at the University of Vienna provides a clearer picture of where these airborne microplastics come from. Using global measurements and computer models, the researchers estimate emissions from both land and ocean sources. Their key finding is striking: more than 20 times as many microplastic particles are released into the air from land than from the ocean. The study was recently published in Nature.

Sources of Airborne Microplastics

Scientists have long known that microplastics are present in the atmosphere worldwide. These particles eventually settle in distant and isolated locations. They originate from direct sources such as tyre abrasion and textile fibers, as well as from previously contaminated land and ocean surfaces that release particles back into the air.

Until now, the scale of these emissions and the contribution of each source were not well understood. Earlier research often pointed to the ocean as the main contributor, but the new findings challenge that assumption.

Comparing Models With Real-World Measurements

To better understand the problem, researchers Ioanna Evangelou, Silvia Bucci and Andreas Stohl compiled 2,782 individual measurements of atmospheric microplastics from studies conducted around the world. They then compared these real-world observations with results from a transport model that incorporated three different published emission estimates.

The comparison revealed a major issue. The model consistently predicted far more microplastic particles in the air and deposited on the Earth’s surface than were actually observed, sometimes by several orders of magnitude. This gap allowed the researchers to adjust the model and refine emission estimates separately for land and ocean sources, producing more accurate results.

Land Dominates Microplastic Emissions

After recalibrating the data, the team found that emissions from land had been significantly overestimated in earlier models, but even after correction, land remained the dominant source. Ocean emissions were also revised downward.

When asked where most airborne microplastics originate, lead author Andreas Stohl explained: “The now scaled emission estimates show that over 20 times more microplastic particles are emitted on land than from the ocean.” At the same time, first author Ioanna Evangelou noted an important detail: “However, the emitted mass is actually higher over the ocean than over land, which is due to the larger average size of oceanic particles.”

Ongoing Uncertainty and Need for More Data

This research marks an important step toward understanding how microplastics move through the atmosphere and spread globally. However, significant uncertainties remain.

“However, the data situation is still not satisfactory, and there are still major uncertainties. More measurements are needed so that we know how much microplastic comes from traffic and how much from other sources. The size distribution of the particles is also highly uncertain, and thus the total amount of plastic transported in the atmosphere,” summarizes Andreas Stohl, lead author of the study.

Key Findings at a Glance

• Globally distributed measurements of microplastics in the atmosphere were compared with model simulations.
• The comparison showed that the model overestimates the number of measured microplastic particles by several orders of magnitude.
• This is a clear indication that the emission estimates used to date are far too high, especially for land-based emissions.
• The number of microplastic particles emitted from land is more than 20 times higher than the number of particles emitted from the ocean.
• More accurate measurements are needed for more precise emission estimates. In particular, the size distribution of plastic particles is a major source of uncertainty that has not been recorded accurately enough in the measurement data to date.

Two new studies published in the journal Nature reveal a surprising pattern. While the planet gradually cooled over this time, levels of heat-trapping greenhouse gases in the atmosphere declined only slightly.

A Long-Standing Climate Mystery

For more than a century, scientists have known that Earth was significantly warmer about 3 million years ago. Evidence includes fossils of temperate and subtropical forests found in places like Alaska and Greenland, as well as ancient shorelines along the U.S. East Coast from Georgia to Virginia, showing that sea levels were much higher.

However, the reason behind this warm period and the cooling that followed has remained unclear. One major challenge has been the difficulty of accurately reconstructing both global temperatures and greenhouse gas levels from so far back in time.

Searching for the Oldest Ice in Antarctica

The new research comes from the National Science Foundation Center for Oldest Ice Exploration, known as COLDEX, a collaborative effort led by Oregon State University. The team focuses on locating and analyzing some of the oldest ice on Earth.

The studies were led by Julia Marks-Peterson, a doctoral student at OSU, and Sarah Shackleton, who conducted the work as a postdoctoral researcher at Princeton University and is now a professor at Woods Hole Oceanographic Institution. They examined ancient ice recovered from Allan Hills, a unique region along the edge of the East Antarctic ice sheet.

Unlike typical ice core sites, Allan Hills contains ice that has been pushed up and distorted by movement within the ice sheet. This disrupts the original layering, so instead of a continuous timeline, researchers get “snapshots” of climate conditions from different points in the past.

“Those snapshots extend climate records from ice much further than previously possible,” said COLDEX Director Ed Brook, a paleoclimatologist in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “These longer records are also now raising new questions about Earth’s climate evolution and how far back in time we might be able to go with ice core data.”

Ocean Cooling Revealed by Trapped Gases

One study used measurements of noble gases preserved in the trapped air bubbles to estimate changes in ocean temperature over time. These gases provide a global signal of ocean conditions.

The results show that average ocean temperatures have dropped by about 2 to 2.5 degrees Celsius over the past 3 million years. While earlier research has documented cooling at the ocean surface, this study found that the timing of cooling differed between surface waters and deeper layers.

“The noble gases in ice provide a unique way to look at ocean temperature change,” Shackleton said. “Other methods can give you information about ocean temperature at a single site, but this gives a more global view.”

Much of the overall cooling occurred early, beginning around 3 million years ago and continuing for about 1 million years. This period coincides with the formation of large ice sheets in the Northern Hemisphere. In contrast, surface ocean temperatures declined more gradually until about 1 million years ago. Researchers suggest this difference may be linked to changes in how heat moves between the ocean’s surface and its depths.

Greenhouse Gas Levels Show Only Modest Change

Using the same ice samples, Marks-Peterson and her team produced the first direct measurements of carbon dioxide and methane levels spanning the past 3 million years.

Their findings indicate that carbon dioxide levels generally stayed below 300 parts per million during this period. Around 2.7 million years ago, levels were about 250 parts per million and then decreased slightly by roughly 20 parts per million by 1 million years ago. Methane levels remained steady at about 500 parts per billion.

Some earlier estimates based on ancient sediments suggested higher carbon dioxide levels, but results have varied. This highlights the importance of extending ice core records further back in time to improve accuracy.

In contrast, greenhouse gas levels today are much higher. According to the National Oceanic and Atmospheric Administration, carbon dioxide averaged 425 parts per million in 2025, while methane reached 1,935 parts per billion.

More Than Greenhouse Gases Shaped Earth’s Climate

The findings suggest that greenhouse gases alone do not fully explain the long-term cooling trend. Other factors likely played significant roles, including changes in Earth’s reflectivity, shifts in vegetation and ice coverage, and variations in ocean circulation.

“Our hope is that this work will refine our view of past warmer climates and sharpen our understanding of how different elements of the Earth system interact,” said Marks-Peterson.

Even Older Ice May Hold More Answers

The research is already leading to new questions. Scientists involved in COLDEX are continuing to explore older ice samples to push the climate record even further back.

Researchers have recently identified ice that may be as old as 6 million years at the base of one core and are now analyzing these samples. New drilling efforts are also underway to locate additional ancient ice.

Scientists are working to improve methods for reconstructing carbon dioxide levels, studying other gases trapped in the ice, and better understanding how very old ice is preserved. These efforts could help identify new sites for future drilling and further expand the record of Earth’s climate history.

COLDEX is supported by the NSF Office of Polar Programs; the Science and Technology Center Program at the NSF Office of Integrative Activities; and Oregon State University. Fieldwork in Antarctica is supported by the U.S. Antarctic Program and funded by NSF. Ice drilling support is provided by the NSF U.S. Ice Drilling Program and ice sample curation by the NSF Ice Core Facility in Denver, Colorado.

Recent discoveries are beginning to change that picture. They show that dinosaurs continued to live in southern Africa long after those dramatic lava flows.

New Dinosaur Tracks on South Africa’s Coast

In 2025, scientists reported dinosaur tracks about 140 million years old on a remote stretch of coastline in South Africa’s Western Cape. These were the first tracks from that time period in the region (the Cretaceous, 145 million to 66 million years ago).

Now, researchers have uncovered even more evidence.

As ichnologists (studying fossil tracks and traces), the team regularly works along the Western Cape coast near Knysna. Most of their research focuses on tracks preserved in coastal aeolianites (cemented sand dunes) that are between 50,000 and 400,000 years old.

During a visit in early 2025, they explored a small outcrop of rock formed in the early Cretaceous Period. It is the only nearby exposure of rock from that time, and much of it is submerged at high tide. The team hoped they might find a theropod (dinosaur) tooth like one discovered there by a 13-year-old boy in 2017.

Instead, they found something far more exciting. Linda Helm, a member of the group, spotted dinosaur tracks. A closer look revealed more than two dozen possible footprints.

A Tiny Site With Big Significance

The Brenton Formation exposure is very small, measuring no more than 40 meters long and five meters wide, with cliffs rising up to five meters above the shore. Finding dozens of tracks in such a limited area suggests that dinosaurs were fairly common in this region during the Cretaceous.

The researchers estimate the tracks are about 132 million years old. That makes them the youngest known dinosaur tracks in southern Africa (50 million years younger than the youngest tracks reported from the Karoo Basin). They also represent only the second known set of Cretaceous dinosaur tracks in South Africa, and the second from the Western Cape. Some tracks are preserved on flat rock surfaces, while others appear in cross section within the cliffs.

Southern Africa’s Dinosaur Fossil Record

Southern Africa holds an extensive record of vertebrate tracks and traces from the Mesozoic Era (the “Age of Dinosaurs,” from 252 million to 66 million years ago, a time span that includes the Jurassic), especially in the Karoo Basin, which is filled with thick layers of sedimentary rock.

Tracks from the Triassic and Jurassic periods are common in Lesotho and nearby regions of South Africa, including the Free State and Eastern Cape.

However, later volcanic activity created the Drakensberg Group, covering many of these fossil-bearing layers with lava. Some dinosaurs may have briefly survived the initial eruptions, but they were likely among the last animals to live in the Karoo Basin at that time.

As the supercontinent Gondwana began to break apart near the end of the Jurassic Period and into the early Cretaceous Period, smaller basins formed in what are now the Western Cape and Eastern Cape. These areas contain limited deposits from the Cretaceous.

Body fossils from these deposits, mainly in the Eastern Cape, include a range of dinosaurs. Among them are the first dinosaur identified in the southern hemisphere, now known to be a stegosaur, along with sauropods, a coelurosaurian, and young iguanodontids.

In contrast, fossil remains from the Western Cape are rare. They include a few isolated sauropod teeth, scattered bones likely from a sauropod, and two finds near Knysna: the theropod tooth discovered earlier and part of a tibia.

Now, attention is turning to footprints instead of bones.

Dinosaurs of Knysna

The newly discovered tracks lie in the modern intertidal zone, where they are covered by seawater at high tide twice a day.

The environment 132 million years ago would have looked very different from today’s coastline, estuary, and developed landscape. At that time, dinosaurs likely moved through tidal channels or along point bars (river beaches), surrounded by vegetation unlike anything in the area now.

The tracks appear to have been made by a mix of dinosaurs. These include theropods and possibly ornithopods (both these kinds of dinosaur were bipedal, walking on two legs), as well as possible sauropods (huge dinosaurs with very long necks and very long tails that were quadrupedal, walking on four legs). Theropods were meat eaters, while ornithopods and sauropods were plant eaters.

Identifying the exact type of dinosaur from footprints alone can be difficult. Theropod and ornithopod tracks can look similar, and sauropod tracks, although larger, do not always show clear toe impressions.

Because of these challenges, the researchers chose not to “over-interpret” the trackmakers. Their study focuses on documenting the presence and abundance of dinosaur tracks from this time period in the Brenton Formation.

More Discoveries May Be Ahead

The presence of early Cretaceous dinosaur tracks in both the Robberg Formation and the Brenton Formation suggests that more sites may still be waiting to be found. Other non-marine Cretaceous rock exposures exist in the Western Cape and Eastern Cape.

Future systematic searches of these areas could reveal additional dinosaur bones, more tracks, and possibly traces of other ancient animals.

Mark G. Dixon and Fred van Berkel of the African Centre for Coastal Palaeoscience, Nelson Mandela University, contributed to this research.

The findings also challenged a popular older idea about snake origins. Instead of beginning as small burrowers, the evidence from Najash pointed to ancestors of modern snakes that were larger-bodied animals with wide mouths. The fossils also showed that early snakes held onto their hindlimbs for a long time before the rise of the mostly limbless snakes alive today.

“Our findings support the idea that the ancestors of modern snakes were big-bodied and big-mouthed — instead of small burrowing forms as previously thought,” explained Fernando Garberoglio, from the Fundación Azara at Universidad Maimónides, in Buenos Aires, Argentina and lead author on the study. “The study also reveals that early snakes retained their hindlimbs for an extended period of time before the origin of modern snakes which are for the most part, completely limbless.”

Hidden skull details inside a 100 million year old fossil

The fossil snakes described in the study came from Northern Patagonia and are closely tied to an ancient southern lineage that lived across the continents of Gondwana. Researchers say that group appears to be related to only a small number of unusual snakes still living today. To see inside the specimen without damaging it, the team used micro-computed tomography (micro-CT) scanning. That let them reconstruct the skull in exceptional detail, including the paths of nerves and blood vessels as well as bones buried inside the rock.

That level of detail helped resolve a long-running anatomical debate. Scientists had misunderstood the jugal bone in snakes and snake relatives for generations, and the Najash fossils gave them direct evidence to correct the record. The study’s authors argued that these new skulls and skeletons clarified the sequence of bone loss that eventually produced the highly specialized skulls of modern snakes.

“This research revolutionizes our understanding of the jugal bone in snake and non-snake lizards,” said Michael Caldwell, professor in the Department of Biological Sciences and Earth and Atmospheric Sciences, and a co-author on the study. “After 160 years of getting it wrong, this paper corrects this very important feature based not on guesswork, but on empirical evidence.”

“This research is critical to understanding the evolution of the skulls of modern and ancient snakes,” added Caldwell.

The paper, “New Skulls and Skeletons of the Cretaceous Legged Snake Najash, and the Evolution of the Modern Snake Body Plan,” was published in Science Advances in 2019.

Later studies added more twists to the snake origin story

Research published after the 2019 Najash paper has made the story even more interesting. In 2020, paleontologists described Boipeba tayasuensis, a Late Cretaceous blind snake from Brazil. That fossil pushed the record of blind snakes deeper into the age of dinosaurs and suggested that some early blind snakes were much larger than their living relatives, topping 1 meter in length. The finding supported the idea that parts of early snake evolution in Gondwana were more diverse, and often bigger-bodied, than once assumed.

Then, in 2023, another Science Advances study approached snake origins from an entirely different angle by reconstructing the brains of living squamates and fossil snakes. That work suggested the ancestor of crown snakes, meaning the group that gave rise to living snakes, may have been adapted for burrowing while also behaving opportunistically. Rather than neatly settling the debate, the result showed that snake origins were likely complex, with different branches of the snake family tree preserving different clues about how body shape, habitat, and feeding style evolved.

A 2025 Nature study added even more context by describing a Middle Jurassic squamate from Scotland with a striking mix of lizard-like and snake-like traits. The authors found that early squamate evolution involved a great deal of anatomical experimentation and convergent evolution, which helps explain why the earliest snake story has been so difficult to untangle from fossils alone.

Why Najash still matters

Even with those later discoveries, Najash remains one of the clearest windows into a crucial stage of snake evolution. It captures a moment when snakes still had hindlimbs, still retained a more lizard-like skull in some respects, and had not yet fully acquired the body plan seen in their modern descendants. That combination is exactly what makes the fossil so valuable. It does not just show an ancient snake. It shows an ancient snake in transition.

The University of Alberta described the work as part of the Faculty of Science’s broader mission as a major center for research and teaching, with a focus on advancing knowledge through classroom, laboratory, and field research.