Wikipedia Deep Dive

Steven E. Koonin

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The Physicist Who Became Climate Science's Most Credentialed Skeptic

In the spring of 1989, the world briefly believed that two chemists in Utah had solved humanity's energy problems forever. Cold fusion—the dream of generating nuclear power at room temperature in a simple laboratory apparatus—seemed tantalizingly within reach. Then Steven Koonin stood up at a meeting of the American Physical Society in Baltimore and ended the dream with a single devastating phrase.

He called the Utah researchers' work "the incompetence and delusion of Pons and Fleischmann."

The room gave him a standing ovation.

This moment captures something essential about Koonin's career: he has made a habit of standing before crowds and telling them that exciting scientific claims don't hold up to scrutiny. In 1989, mainstream science cheered. Three decades later, when he turned that same skeptical lens toward climate science, the reception would be very different.

The Making of a Prodigy

Steven Elliot Koonin was born in Brooklyn on December 12, 1951, and showed early signs of exceptional intellectual ability. He graduated from Stuyvesant High School—one of New York City's elite specialized public schools that admits students by competitive examination—at just sixteen years old. From there he went to the California Institute of Technology, known universally as Caltech, for his undergraduate degree, then to the Massachusetts Institute of Technology for his doctorate in theoretical physics.

His doctoral advisor was Arthur Kerman, a distinguished nuclear physicist at MIT's Center for Theoretical Physics. Kerman's research focused on understanding the behavior of atomic nuclei—the tiny dense cores at the center of atoms where protons and neutrons are bound together by the strong nuclear force. This is physics at its most fundamental: trying to understand the basic building blocks of matter.

In 1975, at twenty-three years old, Koonin returned to Caltech as an assistant professor. He was among the youngest faculty members the institute had ever appointed. He would stay there for nearly three decades, eventually rising to provost—the chief academic officer responsible for the institution's overall academic direction—a position he held from 1995 to 2004.

As provost, Koonin's interests ranged widely. He championed scientific computing, recognizing early that massive computational power would transform how science is done. He pushed the institute toward bioengineering and biology, sensing where future discoveries would emerge. And he shepherded one of astronomy's most ambitious projects: the Thirty Meter Telescope, an enormous instrument designed to collect nine times more light than the largest optical telescopes then in existence. The project continues to this day, though it has been mired in controversy over its proposed location on Mauna Kea, a mountain sacred to Native Hawaiians.

From Academia to Oil

In 2004, Koonin made a move that surprised many in academic physics. He left Caltech to become the chief scientist at BP, the British oil and gas giant formerly known as British Petroleum.

The position put him at the intersection of science, energy policy, and corporate strategy. His official responsibility was guiding BP's long-range technology investments, with a particular focus on alternative and renewable energy sources. This was during a period when BP was actively cultivating a green image—the company had rebranded itself as "Beyond Petroleum" in 2000 and was investing in solar and wind power.

Koonin spent five years at BP, watching the energy industry from the inside. Then came another transition.

Washington Calling

When Barack Obama won the presidency in 2008, he appointed Steven Chu as Secretary of Energy. Chu was himself a Nobel Prize-winning physicist—he had shared the 1997 prize for developing methods to cool and trap atoms using laser light. He wanted another physicist to serve as his Under Secretary for Science, and he recruited Koonin.

The Under Secretary for Science is a significant position. It oversees the Department of Energy's vast scientific enterprise, including the national laboratories that conduct everything from nuclear weapons research to particle physics experiments. Koonin served in this role from May 2009 to November 2011, during a period when the Obama administration was grappling with how to address climate change and promote clean energy.

During his tenure, Koonin led the creation of the department's 2011 Strategic Plan and its first Quadrennial Technology Review, a comprehensive assessment of the nation's energy technology landscape. He was deeply involved in climate research programs and energy technology policy decisions.

It's worth pausing here to note the trajectory. Koonin had served in the Obama administration—not as a political appointee holding ideological positions, but as a scientist helping to craft energy and climate policy. The administration he served under accepted the scientific consensus on climate change and worked to address it. Whatever positions Koonin would later take on climate science, he had been, quite literally, on the inside of Democratic climate policy.

The Cold Fusion Episode

To understand Koonin's later role in climate debates, it helps to look more closely at what happened with cold fusion in 1989.

On March 23 of that year, Martin Fleischmann and Stanley Pons, two electrochemists at the University of Utah, held a press conference announcing that they had achieved nuclear fusion at room temperature. The claim was extraordinary. Normal nuclear fusion—the process that powers the sun and hydrogen bombs—requires temperatures of millions of degrees to force atomic nuclei close enough together that the strong nuclear force can bind them. If fusion could be achieved cheaply and easily at room temperature, the world's energy problems would be solved.

The announcement created a frenzy. Scientists around the world scrambled to replicate the results. The University of Utah, scenting patents and prestige, rushed to protect its intellectual property. The scientific community was split between excitement and skepticism.

At Caltech, Koonin teamed up with two colleagues: Nathan Lewis, an electrochemist, and Charles Barnes, a nuclear physicist. They became known as "the Caltech Three," and they set out to test the Utah claims rigorously.

What they found, and what other research groups around the world were also finding, was that the Utah results couldn't be reproduced. The measurements that Pons and Fleischmann had reported appeared to be the result of experimental errors, not nuclear fusion.

The showdown came at the American Physical Society meeting in Baltimore that May. Koonin and Lewis presented their findings in back-to-back talks that systematically demolished the cold fusion claims. Koonin's characterization of the Utah work as stemming from "incompetence and delusion" was blunt to the point of harshness. He had originally wanted to go further and use the word "fraud," but was counseled against it by colleagues and by Caltech's president.

The cold fusion episode established Koonin's reputation as someone willing to challenge scientific claims publicly and forcefully. In that case, the scientific community ultimately agreed with his assessment. Cold fusion is now regarded as one of the most famous examples of pathological science—research that appears to show positive results but cannot be replicated and is eventually abandoned.

The Climate Turn

After leaving the Department of Energy in 2011, Koonin spent time at the Institute for Defense Analyses, a nonprofit corporation that provides scientific and technical analysis to the federal government on defense and national security issues. Then, in 2012, he became the founding director of New York University's Center for Urban Science and Progress, an applied research center that uses data analytics to address the challenges of city life.

Throughout this period, Koonin maintained various advisory roles. He served on boards for the National Science Foundation, the Department of Defense, and the Department of Energy's national laboratories. He chaired the JASON advisory group, a secretive panel of scientists that provides technical advice to the government on matters of national security. From 2014 to 2019, he chaired a National Academies committee on engineering and physical sciences.

Then, in 2017, Koonin stepped into the climate debate in a way that would define the next phase of his career.

His opening move was an opinion piece in The Wall Street Journal proposing what's known as a "red team/blue team" exercise for climate science. The concept borrows from military and intelligence practices: a blue team defends the established position while a red team tries to poke holes in it. Koonin suggested that such an adversarial review could test whether the scientific consensus on climate change was as solid as claimed.

The idea attracted interest from the Trump administration. In 2018, the Environmental Protection Agency under administrator Scott Pruitt—who had sued the EPA multiple times as Oklahoma's attorney general and expressed skepticism about climate science—proposed a public debate on climate change. According to draft materials that later emerged, Koonin worked with William Happer, a Princeton physicist who would later serve briefly in the Trump White House, to plan the red team/blue team exercises. Happer was also associated with the CO2 Coalition, a nonprofit organization that promotes the view that increased carbon dioxide levels benefit life on Earth.

The EPA debate never materialized. Neither did a proposed "Presidential Committee on Climate Security" that the Trump administration considered creating in 2019 to conduct an "adversarial" review of climate science. Koonin was reportedly involved in recruiting scientists for this effort. The committee was eventually abandoned in favor of a less formal initiative that wouldn't be subject to public disclosure requirements.

Unsettled

In 2021, Koonin consolidated his climate arguments into a book titled Unsettled: What Climate Science Tells Us, What It Doesn't, and Why It Matters. The title itself was a provocation, playing on the common phrase "the science is settled" that climate advocates often invoke.

Koonin's argument, in essence, is that the mainstream presentation of climate science exaggerates what scientists actually know and understand. He points to several themes:

Climate measurement data has significant limitations that make it difficult to separate human influences from natural variability.
Different climate models produce different results, and sometimes those results contradict each other.
Press releases, summaries, and news coverage often don't accurately represent the nuances and uncertainties in the underlying research.
The science isn't mature enough to make reliable predictions about future climate conditions or to know precisely how human actions will affect them.

These arguments were not new—they had appeared in various forms in Koonin's earlier Wall Street Journal essays. But gathering them into a book gave them greater reach.

The response from climate scientists was swift and largely negative.

Gary Yohe, an economist who studies climate policy, wrote in Scientific American that Koonin "falsely suggests that we don't understand the risks well enough to take action." Yohe noted that climate science had been "growing stronger for decades" and that "early indications detected and attributed in the 1980s and 1990s have come true, over and over again and sooner than anticipated."

Raymond Pierrehumbert, a climate physicist at Oxford, called an earlier Koonin essay "a litany of discredited arguments" with "nuggets of truth buried beneath a rubble of false or misleading claims from the standard climate skeptics' canon."

Mark Boslough, a physicist who had actually been Koonin's student, wrote a critical review stating that "Koonin makes use of an old strawman concocted by opponents of climate science in the 1990s to create an illusion of arrogant scientists, biased media, and lying politicians—making them easier to attack."

Other critics noted that Koonin's expertise is in theoretical physics, not climate science specifically, and accused him of cherry-picking data points that support his skeptical narrative while ignoring the broader body of evidence.

The book found supporters too, though they tended to come from conservative institutions. Mark Mills, a senior fellow at the Manhattan Institute, praised it in The Wall Street Journal as "rebutting much of the dominant political narrative." When scientists critiqued Mills's review, Koonin responded with a post on Medium defending his positions.

The 2025 Report

Koonin's influence on climate policy reached a new height in 2025, when he became a coauthor of a controversial Department of Energy report titled "A Critical Review of Impacts of Greenhouse Gas Emissions on the U.S. Climate."

The report's other authors included John Christy and Roy Spencer, both atmospheric scientists at the University of Alabama in Huntsville who have long argued that mainstream climate science overestimates warming; Judith Curry, a former Georgia Tech professor who has become a prominent climate skeptic; and Ross McKitrick, a Canadian economist known for critiquing the famous "hockey stick" graph of historical temperatures.

The report asserted that the dangers from greenhouse gas emissions have been exaggerated. In interviews, Koonin claimed that ninety-five percent of the report drew from the United Nations Intergovernmental Panel on Climate Change, the body that periodically synthesizes climate research from around the world.

Critics accused the report of cherry-picking IPCC findings and highlighting uncertainties in ways designed to downplay climate impacts. Several scientists whose research was cited in the report said their work had been mischaracterized.

What to Make of Koonin

The arc of Steven Koonin's career presents an unusual puzzle. Here is a scientist of unquestioned credentials—Caltech faculty at twenty-three, provost of one of the world's premier research institutions, member of the National Academy of Sciences, Under Secretary in a Democratic administration. He is nobody's idea of a crank.

And yet the positions he has taken on climate science place him sharply at odds with the overwhelming consensus of researchers in the field. When he stood before the American Physical Society in 1989 and declared cold fusion the product of incompetence and delusion, the scientific community rallied to his side. When he published Unsettled in 2021, climate scientists lined up to call it misleading.

One interpretation, favored by Koonin's critics, is that his background in theoretical physics and computational methods doesn't give him the specialized knowledge to evaluate climate science competently, and that he has been influenced by his years at BP and his connections to conservative institutions like the Hoover Institution, where he became a fellow in 2024. In this view, Koonin is an example of how credentials in one scientific field don't automatically transfer to another, and how institutional affiliations can shape intellectual positions.

Another interpretation, which Koonin himself advances, is that he is simply applying the same skeptical methodology that served him well in the cold fusion controversy. In this view, climate science suffers from groupthink and institutional pressures that suppress legitimate uncertainty, and Koonin is one of the few scientists with the standing and courage to point this out.

What's clear is that Koonin has become one of the most influential figures in the effort to challenge mainstream climate science. His credentials make him difficult to dismiss as a fringe figure, even as climate scientists argue that his specific claims don't hold up. He represents a particular kind of dissent: not the denial that the climate is changing, but the argument that we don't understand it well enough to justify dramatic policy responses.

In the climate debate, that position occupies its own contested territory—not quite denialism, but not acceptance either. A kind of scientific uncertainty weaponized, his critics would say. A call for rigor and humility, his supporters would counter.

Standing ovations are harder to come by the second time around.