Sixty years ago this month, one of the most audacious attempts at changing the weather was made. On October 13, 1947, a hurricane about 500km (300 miles) off the east coast of Florida and Georgia was sprayed from aircraft using frozen carbon dioxide, known as dry ice. The idea was to trigger more rain from the clouds and help to defuse the storm.

However, six hours after the spraying operation, the hurricane gained strength, lurched 90 degrees towards the coast and tore into Savannah, Georgia, where it caused $2 million worth of damage.

The US military, which co-sponsored the project, classified the data on it to frustrate any litigation. However, meteorologists later showed that the hurricane had already begun to change direction when the seeding was carried out. And a tropical storm in the same area a week earlier had executed a similar change in track.

But over the next 30 years the US military made more attempts to modify hurricanes. Planes seeded the strongest winds of the hurricane, around the eye of the storm, with silver iodide to try to weaken the winds.

However, the results could not distinguish between the natural behaviour of hurricanes and the effect of spraying.