Steven Siems

The last Rainmaker

Associate Professor Steven Siems is examining the world's first instance of significantly enhancing rain through the intentional dispersal of substances into the air, in a process known as cloud seeding.

'There have been many controversial results; there have been some unscrupulous, controversial scientists in the field, too. As a result, people tend to stay away from this field. However, down in Tasmania, cloud seeding has been going on and off on its own for almost forty years, and quite surprisingly, we found that they were getting some 5 to 11 per cent increase in rainfall per month.'

From examining satellite observations, Steven has helped determine that cloud seeding may be successful only in very specific areas - another of which might also be mainland Australia's Snowy Mountains. If successful, a cloud seeding operation there will lead to greater water flow into the Murray-Darling Basin.

Cloud seeding has been something of a hit-and-miss affair, even for Steven.

'We've had a similar project up in Queensland. They wanted to do a flavour of cloud seeding three or four years ago when they were in the midst of a severe drought and water shortages. Scientifically it came out with limited results, but it's been the basis for some really interesting studies. We now better understand the nature of the variability up there - how you can go from severe drought for years, then go to massive flooding.'

Steven is quick to point out that such manipulation of the hydrologic cycle is not uncommon.

'As far as trying to divert a little bit of rainfall in select locations - I don't see how that's much different from irrigation in general. Changing a river to go here, pulling some water out there, trying to do that, ethically I find that comparable. Moreover, it's not like your stealing water from there to put it up there. This is rain that was never going to fall.'

However, Steven is wary should we take such geoengineering too far.

'Putting in aerosols into the stratosphere to combat climate change should only be used as a last resort. It's so dangerous - we don't know the repercussions, and we don't understand what could happen when we start mucking with the climate on a global scale. I don't mean to be alarmist, but there is the potential that we're marching to a pretty grim, disruptive future. A four-degree increase in global temperatures - which might well be what we'll see - is something that should really worry us. Still, the idea of changing the atmosphere like that scares me.'