In my previous post, “Pollution Without Borders: What Atmospheric Science Teaches Us About Global Connections,” I introduced readers to Dr. Jim McQuaid, an atmospheric scientist whose career has taken him from the Sahara Desert to Indonesian peatlands, always chasing gases and particles, and processes that tie our air together. I recommend starting there for a sense of Jim’s wide-ranging perspective on the atmosphere as one of Earth’s great connectors.
This post takes a closer look at one of the projects I found most fascinating in our conversation: Black and Bloom, a major research effort to understand how airborne particles, and even living microorganisms, are accelerating the melt of the Greenland Ice Sheet. Along the way, I’ll share some of Jim’s reflections on long-range transport of pollutants, global justice, and how communities and young scientists alike can engage with the challenge of air pollution.
Catching the Same Breath, Four Times
In 2004, Jim was part of a project called the International Transport of Ozone and Precursors (ITOP), which aimed to track how air masses crossed the Atlantic. “We had three different aircraft involved,” he recalled, “and we managed to intercept the air traveling across the Atlantic four times.”
First, a pair of American aircraft each sampled the air as it left the U.S. East Coast. Then the U.K.’s BAe-146 research aircraft (based in the Azores, a group of islands in the middle of the Atlantic) and a German Falcon jet (based on the French coast) tracked it again as it moved toward Europe. To their amazement, the same air mass later looped back over the Atlantic, where it was intercepted a final time!
What made this extraordinary wasn’t just the choreography of aircraft—it was the science. Each time, the team checked the “chemical fingerprint” of the air, comparing ratios of gases and particles that react away at predictable rates. The signatures matched. Against all odds, they had followed the same packet of polluted air across thousands of kilometers, proving in real time that pollution ignores borders.
That insight continues to shape Jim’s perspective on global connections.
Pollution Without Borders, Justice Without Boundaries
Jim explained it simply: “In the Northern Hemisphere, a lot of polluted air crosses the Atlantic from North America to Europe. Then Europe pollutes China, and China in turn pollutes the west coast of America as the air is blown across the Pacific.”
What does that mean for fairness? It means the place where pollution lands isn’t always the place that caused it. A child in the U.K. breathing in air laced with soot might be suffering consequences of industries thousands of miles away. A farmer in Asia might feel the health costs of emissions produced in Europe.
This global “pass-the-parcel” of pollution underscores why climate and air quality must be understood as shared responsibilities. No single country can shield itself by tightening only its own borders; the atmosphere doesn’t recognize passports.
Black and Bloom: When Dust and Microbes Darken the Ice
Nowhere is this global interplay of air and earth more dramatic than on the Greenland Ice Sheet. The second largest in the world, it stores enough frozen water to raise global sea levels by more than seven meters if it melted completely. Already, its melt rate is accelerating under climate change.
The Black and Bloom project, led by a team of U.K. and European researchers, including Jim, set out to understand one piece of this puzzle: why the western edge of the ice sheet, known as the “Dark Zone,” was absorbing more sunlight and melting faster.
Two culprits stood out. The “black” referred to particles—soot, dust, and other impurities—delivered by the atmosphere and deposited on the ice. These particles darken the surface, lowering its albedo (reflectivity), so it absorbs more of the sun’s heat.
The “bloom” referred to something living: pigmented glacier ice algae that thrive in meltwater pockets. Fed in part by nutrients delivered by that same atmospheric dust, these microbes multiply, forming blooms that further darken the ice.
The research showed that locally derived dust plays an especially important role. In field campaigns on the Dark Zone, Jim and his colleagues found that fine silicate dust blowing from newly ice-free ground carried phosphorus, an essential nutrient. The concentrations they measured were enough to fuel algal blooms at levels similar to what they saw thriving on the ice itself.
In other words, as the ice sheet retreats, exposing more forefield ground, it creates more local dust, which fertilizes more algae, which darkens more ice, which accelerates more melt—a feedback loop driven in part by airborne transport.
This is why Jim’s atmospheric perspective is vital. It isn’t just glaciers and microbes; it’s dust storms, wind patterns, and chemical signatures that connect them.
From the Ice Sheet to the Schoolyard
As striking as these global stories are, Jim is equally committed to the local and personal. In West Yorkshire, he’s worked with schools and communities to measure air quality using both advanced and low-cost sensors.
The key, he said, is communication: “The most important thing is always to reduce the amount of complicated scientific terms and turn what you’re trying to communicate into language that people understand.” To make concepts tangible, he often starts talks by sharing a surprising fact: while it may seem strange to think of air as having weight, the average person breathes in more than 10 kilograms (22 pounds) of air every day, far more than the combined weight of everything they eat or drink. “That usually gets their attention!” he laughed. He looks for what he calls the “lightbulb moment”—that glint in someone’s eye when an abstract concept suddenly makes sense.
That’s where low-cost sensors have real potential. While reference-grade instruments remain the gold standard, they’re expensive and rare. Sensors that can be deployed near homes, schools, and playgrounds bring air monitoring close to where people actually breathe. And because they’re local, people pay attention: “It’s making the measurement of the air that they are directly breathing, or their children are directly breathing.”
Jim acknowledges it may sound like “tugging at heartstrings,” but protecting children’s health is exactly the kind of motivation that gets people to care—and act—on air pollution.
Advice for My Generation
Finally, I asked Jim what matters most for young people like me who want to enter this field. His answer surprised me: it wasn’t just technical skills.
“Yes, you need numeracy, you need to be comfortable with graphs and data,” he said. “But the most important thing is to be inquisitive, to have a passion to understand why things are happening.”
That curiosity often comes with a personal connection. Many of his Ph.D. students, he noted, are international, driven by the desire to bring knowledge back to their own countries to improve health and air quality there.
And just as important is the ability to translate science into accessible ideas. Jim often explains particle pollution by comparing the human body to a sieve: larger particles get caught in the upper airways, but tiny PM2.5 particles slip deeper into the lungs, and the tiniest, or ultrafine particles, even cross into the bloodstream and deep into the organs, including across the blood-brain barrier. That metaphor sticks with people in a way raw data cannot.
Why It Matters
What I take from Jim’s stories is that the atmosphere is both vast and intimate. It carries air masses across oceans, linking continents in unseen flows of pollution. It carries dust across ice sheets, fertilizing microbes that reshape global sea levels. And it carries the air we breathe into our bodies and our children’s bodies every day.
The challenge of pollution without borders is daunting. However, projects like Black and Bloom demonstrate that science can unravel these hidden pathways. Community monitoring shows us that local action is feasible. And the advice Jim gives—be curious, be clear, be passionate—reminds us that the next generation of scientists and citizens can rise to meet it.
✦ If you haven’t already, you can read my first interview with Dr. McQuaid here. In that post, we explored his career journey and the big-picture connections between pollution, climate, and justice.