Cloud Seeding (continued)

Allan Rainbird reports that when he was a forecaster in Sydney prior to moving to the Hydrometeorological Section in Melbourne he spent two weeks in the New England region of NSW establishing a network of rain gauges for the CSIRO cloud seeding group. He states that there was no further contact from the group but he understands that it was concluded that if seeding had any effect it decreased rainfall.

Allan found his attachment to the SMHEA from September 1960 to August 1961 a very interesting and rewarding experience. He was located in the Field Investigation Division headed by Darcy Walsh and gained a great deal from his association with engineers in the Division who had worked with the US Bureau of Reclamation.

The CSIRO cloud seeding exercise had concluded by the time Allan arrived in Cooma but a debate still raged between CSIRO and the SMHEA on interpretation of the results. It was agreed to employ a US expert (Roscoe Braham) to assess results. Braham discovered that the person with the task of drawing isopleths of rainfall over the target and control areas knew the result of the random decision on whether the seeding should take place. Braham immediately abandoned his investigation. Jack Wiesner (formerly a member of the staff of the Bureau's Sydney Divisional Office) was engaged as a consultant to draw the isopleths. After all this effort the evaluation of the effect of cloud seeding was inconclusive although the CSIRO considered that seeding had been successful.

The investigation of the results of CSIRO cloud seeding was one of the many tasks Len Dwyer gave Gerry O'Mahony after his return from ANU. Gerry was extremely doubtful about the validity of the design of experiments and the statistical techniques employed in assessing success. He was acquainted with Alf Cornish, Head of CSIRO Statistical Division, who shared Gerry's scepticism about design and statistical techniques.

I recall an occasion in the late 1950s or early 1960s when people from the Bureau and CSIRO met in Len Dwyer's office to discuss cloud seeding. CSIRO was represented by Fred White, Taffy Bowen and Pat Smith, the Bureau by Len Dwyer, Gerry O'Mahony and myself. The discussion became somewhat tense when in reply to a CSIRO statement Gerry said "anyone who believes that should see a psychiatrist", to which Taffy replied "hands up those who want to see a psychiatrist". Only Taffy's and Pat Smith's hands were raised. The dispute with CSIRO on cloud seeding continued until the project was abandoned by CSIRO in 1980.

Gerry has made available a clipping from the Melbourne newspaper Weekly Times of 6 September 1967 which reports that, at a meeting of the WRF when the debate still raged, Mr J. McCann, senior economist with the Victorian Department of Agriculture, had estimated that "$2 million had been added to value of the district's wheat crop by rainfall increases brought about by cloud seeding". The same article reports Gerry's scepticism which was based on his examination of rainfall data from the area seeded.

Gerry has told me that during the discussion following the presentation to the WRF meeting he had stated that only two conclusions could be drawn from the fact that rainfall upwind of the seeding had increased as much as rainfall in the seeded area. He went on to explain that one remote possibility was that the seeding agent had been blown in the westerly wind right round the southern hemisphere and had seeded the area upwind. An observer asked the question that Gerry had anticipated in only revealing one of his conclusions. The questioner asked what was the other possible conclusion. Gerry responded "the only other possible conclusion is that these claims are a bunch of codswallop".

Bureau of Meteorology