Earth has a natural thermostat that has kept the planet habitable for more than a hundred million years. Scientists have struggled to fully explain how it works, but new research identifies a missing link between phosphate availability and sea level. Temperature influenced the size of polar ice sheets and sea level. Sea level changes drove the availability of this nutrient and controlled how much carbon was buried in the ocean, which in turn regulates how much carbon dioxide stays in the atmosphere and how warm or cool the planet runs.

 co-authored by , professor of Earth and environmental sciences in the University’s , traces how fluctuating sea levels and dissolved oxygen content controlled the availability of phosphate in the ocean and atmospheric carbon dioxide accumulation stretching across the last 60 million years. The research was published in .

“We know that atmospheric carbon dioxide decreased substantially as Earth cooled over the last 60 million years, but we have had remarkably little understanding of where that carbon ended up,” says lead author , professor of Earth sciences at the University of Oxford, . “Our results suggest that enhanced burial of organic carbon in marine sediments played a much more important role than was previously appreciated.”

The key to the study is phosphorus, specifically phosphate, an essential nutrient for marine life that the researchers describe as a previously “invisible” piece of the puzzle. At high sea levels, broad continental shelves efficiently trapped phosphate in shallow sediments, starving the open ocean of the nutrient. With less phosphate available, marine productivity declined, less organic carbon was buried on the seafloor and the ocean became well-oxygenated—while carbon dioxide built up in the atmosphere.

As sea levels fell, that dynamic reversed. Shrinking shelves released more phosphate into the water column, fueling a bloom in marine life. As that organic matter sank and decomposed, it consumed oxygen from the water until low-oxygen zones began to emerge. When those low-oxygen zones extended into contact with carbon-rich shelf sediments, they triggered a feedback loop in which oxygen-poor conditions caused more phosphate to be released from sediments, driving further organic carbon burial and pulling CO2 out of the atmosphere.

“Our co-author, Christian Bjerrum, studied the connection among sea level, ocean oxygen and phosphate with a computer model two decades ago,” Lu says. “We finally pieced together the geologic records necessary to test this hypothesis.”

The researchers identified a sea-level “sweet spot,” roughly 10 to 40 meters above modern sea level, where this feedback was most powerful. At that range, oxygen minimum zones overlapped precisely with the organic-rich sediments of the continental shelf, maximizing carbon burial for millions of years at a time. The team matched these patterns against 60 million years of geological data, including carbon isotope records, phosphorus accumulation rates in deep-sea sediments and a novel iodine-to-calcium proxy developed to reconstruct past ocean oxygen levels.

Lu’s lab conducted the iodine-to-calcium measurements, a technique that uses the chemistry of ancient foraminifera, microscopic marine organisms preserved in seafloor sediments, to reconstruct oxygen conditions in the ancient water column. Samples were analyzed using a mass spectrometer at Syracuse University, funded by the National Science Foundation.

The Eocene epoch, which lasted from roughly 56 to 34 million years ago, stands out as a period when this carbon burial mechanism was effectively switched off. Sea levels were at their highest, shelves were flooded, phosphate was efficiently buried in shallow sediments and the ocean was highly oxygenated. Without the feedback loop, carbon accumulated in the atmosphere and the planet remained warm.

Over geological time, the study proposes, the zone for carbon burial has narrowed as oxygen minimum ranges have deepened—a process that has progressively stabilized both atmospheric oxygen and carbon dioxide. The oscillations between carbon burial and atmospheric accumulation have grown more muted, making Earth’s climate system increasingly resilient.

Key Takeaways From the Study:

• Phosphate, an essential nutrient for marine life, acted as a hidden regulator of Earth’s carbon cycle for the last 60 million years — but how it plays this role exactly has not been fully understood.
• Sea level controlled how much phosphate was available in the open ocean, which determined how much carbon was buried in seafloor sediments and how much carbon dioxide accumulated in the atmosphere.
• A sea-level “sweet spot” — roughly 10 to 40 meters above modern levels — maximized carbon burial for millions of years at a time, acting as a natural brake on warming and helping drive Earth’s transition to today’s cooler climate.

The research was conducted with collaborators at the University of Oxford (Rickaby and ) and the University of Copenhagen () and was supported by two National Science Foundation grants.

The new findings build on a body of research from Lu’s lab using the iodine-to-calcium proxy to reconstruct past ocean oxygen conditions. An earlier study, published in January in Nature Geoscience, used the same technique to reveal that —the exact reverse of today’s pattern—and that a planetary tipping point hundreds of millions of years ago flipped that distribution.

Syracuse University today announced the launch of a sweeping for Fall 2026, giving students an unusually complete set of pathways into one of the most consequential fields of the century.

The portfolio includes standalone �����������ǰ�’s and �������ٱ��’s degree programs, cross-disciplinary minors, hands-on co-curricular opportunities and research that together make up a single, coherent ecosystem.

“While AI degree programs are proliferating nationally, few institutions are bringing the full picture to market at once,” says , vice chancellor, provost and chief academic officer. “This is an entire environment for students who want to master AI and shape what it becomes. Whether they want to build the technology, govern it or apply it to a wide range of disciplines, there is now a clear path for these students at Syracuse.”

Academic Opportunities in AI

The Syracuse AI portfolio includes new and degrees in artificial intelligence science; a new �����������ǰ�’s degree in ; a �������ٱ��’s degree in ; seven AI minors; a broad research portfolio across multiple schools and colleges; and a peer-led bootcamp designed to provide students with hands-on AI experience as soon as they arrive on campus.

“Artificial intelligence isn’t confined to a single classroom or discipline at Syracuse University—it’s woven into how our students learn, how our faculty conduct research and how we prepare graduates for a workforce being reshaped by this technology,” says , senior vice president for digital transformation, chief digital officer and interim dean of the . “From new degree programs to cross-campus research initiatives, we’re building an AI portfolio that reflects both the urgency and the opportunity this moment demands.”

The breadth and depth of this portfolio are what distinguishes the Syracuse approach. The �����������ǰ�’s in integrative artificial intelligence is designed for students who want to combine AI with other interests, from public affairs to design to the life sciences. The seven new minors let students in any major add AI fluency in areas like policy, ethics and data. And the AI Bootcamp, a student-led program offering stackable microcredentials, provides students with AI immersion even before they declare a major.

Students are also driving the momentum through the student-led AI organization, United AI, which gives undergraduates hands-on research experience through its Foundry program, cross-campus education initiatives and direct partnerships with leading AI companies.

“Students don’t experience AI as a single subject, and we didn’t want to teach it that way,” says , interim dean of the and associate provost for academic programs. “We built this portfolio so that a future engineer, a future policymaker and a future artist can all find a serious path into AI here and can start the moment they arrive on campus.”

Robust Research

Syracuse University boasts a robust and growing portfolio of research and creative activity related to artificial intelligence. With work spanning engineering, computer science, law, public policy, communications and the humanities, faculty and students are applying AI to challenges ranging from cybersecurity and health care to media literacy and the arts. This interdisciplinary momentum reflects the University’s commitment to advancing AI research that is both technically rigorous and grounded in real-world impact.

“Our faculty are not studying artificial intelligence in the abstract,” says , vice president for research. “They are building systems that detect synthetic media, investigating how algorithmic decision-making affects communities, developing new approaches to cybersecurity and creating new AI capabilities beyond today’s large language models. Students who come to Syracuse will learn from researchers who are actively shaping how AI is built, governed and understood.”

Learn more about artificial intelligence at Syracuse University by visiting .

The Syracuse Center of Excellence in Environmental and Energy Systems (SyracuseCoE) will serve as the organizing host of Healthy Buildings 2027 America, a flagship conference of the . The conference will be held June 20–23, 2027, in Syracuse.

Under the theme “Intelligent Environments: Designing, Retrofitting and Operating for a Healthy, Affordable and Resilient Future,” the conference will bring together subject matter experts from around the world, including researchers, architects, engineers, public health experts and policymakers, to address challenges in the built environment.

Keynotes, panels and breakout sessions will highlight scalable, effective and efficient technologies, collaborative design methods and practices, and policy pathways to healthier indoor environments across all building types and communities.

Healthy Buildings 2027 America will be chaired by Conference President , Ph.D., and Conference Co-President , Ph.D. The conference organizing committee leverages the expertise of faculty from the , , and , as well as the State University of New York’s .

The expertise will span disciplines that include mechanical engineering, civil and environmental engineering, geography, public health, architecture and chemistry. The scientific committee is composed of international experts in indoor environmental quality, building science, health and wellness.

Creating a Healthy Building Environment

“We are thrilled to welcome the global healthy buildings community to Syracuse again in 2027,” says Dong, SyracuseCoE’s co-director and Traugott Professor of Mechanical and Aerospace Engineering in the College of Engineering and Computer Science. “This conference is a celebration of collaboration, bringing together brilliant minds from across the world to share ideas, forge new partnerships and shape a future where every person, in every building, can have a healthy indoor environment. We look forward to an inspiring and transformative conference.”

“We look forward to welcoming everyone to Syracuse for an intellectual and enjoyable conference,” says Zhang, SyracuseCoE’s executive director and interim department chair of mechanical and aerospace engineering in the College of Engineering and Computer Science. “There is so much to discover and exchange to advance science and technology for the built environment.”

The goal of the Healthy Buildings conference series is to advance intelligent, inclusive, cost-effective and future-ready solutions to the converging challenges of climate change, public health disparities, aging infrastructure and rising construction costs. The conference will cover research themes, including the following:

• AI Applications in Healthy Buildings
• Smart Health Monitoring and Control
• Advanced and Sustainable Materials
• Retrofit and Resilience Strategies
• Intelligent New Building Design and Life Cycle Analysis
• Community-Scale Intelligence and Public Health
• Occupant Behavior, Health and Wellness in Buildings

“ISIAQ is very excited about the innovative slate of topics to be presented at the Healthy Buildings conference, as they are critically important to everyone interested in indoor environments around the world,” says Professor , ISIAQ President.

Healthy Buildings 2027 America will take place at the Marriott Syracuse Downtown in Syracuse. Abstract submissions open this month, and sponsorship opportunities are available. Conference registration will open in 2027. For more information, visit .