The New York Times reports: A new study of images apparently from the Syrian attack last month concludes that the rockets delivering toxic sarin gas to neighborhoods around Damascus held up to 50 times more nerve agent than previously estimated, a conclusion that could solve the mystery of why there were so many more victims than in previous chemical attacks.

The study, by leading weapons experts, also strongly suggests that the mass of toxic material could have come only from a large stockpile. American, British and French officials have charged that only the Syrian government and not the rebels was in position to make such large quantities of deadly toxins.

Secretary of State John Kerry told Congress, in hearings on Tuesday and Wednesday, that the United States believes the Syrian military was responsible for the attack, and in classified briefings officials have pointed to Unit 450, which controls Syrian chemical weapons.

The new study was conducted by Richard M. Lloyd, an expert in warhead design, and Theodore A. Postol, a physicist at the Massachusetts Institute of Technology. They based their investigation on scores of online videos and photographs posted since the Aug. 21 attack sent thousands of sick and dying Syrians to hospitals in the Damascus suburbs.

In interviews and reports, the two weapons specialists said their analysis of rocket parts and wreckage posted online suggested that the warheads carried toxic payloads of about 50 liters (13 gallons), not the one or two liters (up to half a gallon) of nerve agent that some weapons experts had previously estimated.

“It’s a clever design,” Dr. Postol said of the munitions in an interview. “It’s clever not only in how it was implemented but in the effectiveness of its dispersal. It accounts for the large number of causalities.”

Shortly after the attack, some analysts said they doubted if the identified rockets could have carried enough nerve agent to have caused the mass casualties. Mr. Lloyd and Dr. Postol say their analysis explains how the misidentification of a central rocket part resulted in the excessively small payload estimates.

In an interview, Mr. Lloyd said the manufacture of the rockets, if not the deadly nerve agent, appeared to be within the capabilities of both the Syrian government and the rebels.

But Stephen Johnson, a former British Army chemical warfare expert who is now a forensic expert at Cranfield University, at Shrivenham, said if the estimate of a 50-liter payload was correct, only the Syrian government could have achieved such a large volume of production.

“That’s a fairly substantial amount to produce yourself and beyond the opposition in its wildest dreams,” he said. Suggestions that the Syrian rebels seized or secretly obtained such amounts, Mr. Johnson added, lacked credibility. “It’s more supportive of the argument that it was the government,” he said. [Continue reading…]