The impact crater in Khan Shaykhun, Syria, believed to be the source of the sarin that killed more than 80 people.

OMAR HAJ KADOUR/AFP/Getty Images

Scientists clash over paper that questions Syrian government’s role in sarin attack

On 4 April 2017, a chemical attack killed more than 80 people in the Syrian town of Khan Shaykhun—a crime that shocked the world and led U.S. President Donald Trump to fire 59 cruise missiles at a Syrian air base. U.S. intelligence agencies saw clear evidence the Syrian government had dropped a bomb filled with the nerve gas sarin on the rebel-held town. Six months later, the Joint Investigative Mechanism (JIM) of the United Nations and the Organisation for the Prohibition of Chemical Weapons concurred.

Now, a manuscript questioning that conclusion has caused a heated dispute among U.S. scientists. Until this week, the paper was scheduled for publication by Science & Global Security (SGS), a prestigious journal based at Princeton University. But as Science went to press, SGS’s editors suspended publication amid fierce criticism and warnings that the paper would help Syrian President Bashar al-Assad and the Russian government. Both have denied that Syria is responsible.

The paper’s most prominent author is Theodore Postol, professor emeritus at the Massachusetts Institute of Technology in Cambridge and a respected expert on missile defense and nuclear weapons. In blog posts and interviews, Postol has argued that the Syrian regime is not responsible for the Khan Shaykhun chemical attack and two others he has examined. Gregory Koblentz, a biological and chemical weapons expert at George Mason University in Fairfax, Virginia, says Postol has disregarded overwhelming evidence and has a pro-Assad agenda, which Postol denies. “I’m not trying to take sides,” he says.

Applied mathematician Goong Chen of Texas A&M University in College Station launched the study after his son told him about Postol’s previous work on the Syrian conflict. He set out to model what happened in Khan Shaykhun and later contacted Postol and five other scientists to work with him. Their manuscript focuses on a small impact crater in a road believed to be the site of the sarin release. Based on photos, satellite images, munitions remnants, and witness interviews, JIM has concluded that the hole, about half a meter deep, was caused by a bomb dropped from an airplane, implicating the Syrian government. But Chen’s models suggest it could have been formed by a 122-millimeter (mm) artillery rocket armed with a small explosive warhead, a weapon on which the Syrian government does not have a monopoly.

An online copy of the manuscript drew little attention until Democratic presidential candidate Tulsi Gabbard, a U.S. representative from Hawaii who met Assad in 2017 and believes he has been unjustly accused of some chemical attacks, discussed it on her campaign website. On 13 September, the investigative website Bellingcat published a detailed critique of the paper. It argued that the crater simulated in the team’s models does not match the one in Khan Shaykhun and does not look like real-world craters formed by 122-mm artillery rockets. Jean Pascal Zanders, an independent researcher and consultant on chemical weapons in Ferney-Voltaire, France, says the manuscript ignores other evidence, such as chemical clues indicating the sarin released in Khan Shaykhun was produced from Syrian government stocks of a precursor.

Postol says Bellingcat’s founder, U.K. journalist Eliot Higgins, “has no scientific training, knows no science, and is not interested in learning any science.” He says he has looked at other evidence as well and now believes there was no sarin attack at all, but that local people made it look like one occurred. The investigation reports were faked to justify the U.S. missile attack, Postol says.

In hindsight, we probably should have sent it to a different set of reviewers.

Pavel Podvig, Science & Global Security

Koblentz wrote several emails to Pavel Podvig, one of the journal’s three editors, urging him not to publish the paper. Koblentz didn’t question the computer model, which he says he is not qualified to judge, but said Postol’s past statements disqualified him. “You must approach this latest analysis with great caution,” Koblentz wrote to Podvig. The paper would be “misused to cover up the [Assad] regime’s crimes” and “permanently stain the reputation of your journal,” he warned.

In a message posted earlier this month, SGS editors said they planned to publish an edited version of the manuscript that should be judged on its merits. “We understand that while no analysis in this field can be completely dissociated from its political context, the scientific community has well-established practices for dealing with this challenge,” they wrote. But on 24 September, they backtracked. An “independent, internal review” had “identified a number of issues with the peer-review and revision process,” a new note reads, leading the editors to put the paper on hold and “examine whether the editors can rectify the problems.” Podvig declined to elaborate but says: “In hindsight we probably should have sent it to a different set of reviewers.”

Koblentz says he welcomes the decision and hopes SGS will open up about what happened. “I think it would be valuable for [scientists in the field] to understand what went wrong,” he says. But Chen says the move “stunned” him, and Postol says he is “totally confident” SGS will eventually publish the paper. He says Koblentz’s criticism is beside the point. “I find it troubling that his focus seems to be on his conclusion that I am biased,” he says. “The question is: ‘What’s wrong with the analysis I used?’”