Rainmaking experiments blamed for landslide which killed 30

The makers of the BBC Radio 4 programme, The Day They Made It Rain, allege that new evidence from previously classified government files suggests that a team of scientists working with the RAF was experimenting with artificial rainmaking in southern Britain in the same week before the Lynmouth disaster and could possibly be implicated. On 15 August 1952, 30 people were killed when 90 million tonnes of water and thousands of tones of rock destroyed many village buildings after running off Exmoor.

According to the programme, the navigator involved in the so-called Operation Cumulus, John Hart, remembers the success of the experiments. “We flew straight through the top of the cloud, poured dry ice down into the cloud,” he said. “We flew down to see if any rain came out of the cloud and it did about 30 minutes later.”

The programme also alleges that recently released documents in the Public Record Office show that these experiments did occur from 1949 to 1955, including information that Operation Cumulus occurred between 4-15 August 1952. Meteorological (Met) Office reports describe flights to collect in-depth data on cloud formation and changes, while a Radio 4 broadcast from the time described pilots flying over Bedfordshire spraying salt, which led to a heavy downpour some 50 miles away over Middlesex.

“I was told that the rain had been the heaviest for several years, and all out of a sky which looked summery,” said aeronautical engineer, Alan Yates, working with Operation Cumulus at the time. “There was no disguising the fact that the seedsman had said he’ed make it rain, and he did….it was not until the BBC news bulletin [about Lynmouth] was read later on, that a stony silence fell on the company.”

Rainmaking experiments were allegedly carried out for defence purposes, whereby torrential rain would impede the advance of an enemy. The most common method involved firing particles of salt, dry ice, or silver iodide into clouds, which would then precipitate, pulled down below freezing point by the weight of the dense particles, making it rain heavily. It was claimed that silver iodide could cause a downpour up to 300 miles away.

However others are more sceptical of the claims. “According to documentary records, there were no cloud seeding experiments until after 1955 and after that date the experiments were always very inconclusive,” Sean Clarke, a spokesperson for the Met Office told edie. “Comparable events to the disaster at Lynemouth have occurred naturally, such as the Hanstead storm of 1975. We believe it was a culmination of heavy rainfall and runoff from Exmoor which made the likelihood of a landslip quite high.”

The British Geological Survey’s Principal Geologist in Exeter, Dr. Richard Scrivener, told edie that at the levels of detection they used in a recent survey of the soil in the Lynmouth area, no traces of silver iodide were found, and that although Exmoor had traces of silver in its soil, this was only to be expected due to the natural makeup of the land.