Our never-ending quest to identify all the amplifying climate feedbacks takes us back to Australia:

THE worst drought in a century, especially in Australia's most populated and fastest growing regions, has forced state governments to make expensive, and in some quarters unpopular, decisions to secure water supply.

As rainfall dwindles, new dams are a less-than-promising prospect, so governments have looked to the boundless resource surrounding us -- the sea -- for an answer. Their solution: desalination....

The Bureau of Meteorology, in its annual climate statement for 2007, "warns of a drying trend in the decades ahead." I noted last year that one Australian newspaper reported

... drought will become a redundant term as Australia plans for a permanently drier future, according to the nation's urban water industries chief.... "The urban water industry has decided the inflows of the past will never return," Water Services Association of Australia executive director Ross Young said.

People, however, need water. And even though many Australian kids now "use timers to take two minute showers, and collect the water in buckets so it can be re-used in the garden"(see "What climate change drives behavior change"), conservation is not enough for some:

Four states -- Western Australia, Queensland, South Australia and NSW -- either have working desalination plants or are planning to build them. Opponents say that producing the large amount of electricity required to run a desalination plant hastens climate change, which may be the culprit behind Australia's drying trend. The scientific jury is still out.

Actually, I don't think you'll actually find very many climate scientists who believe the jury is out on whether human-caused climate change is a major contributor to Australia's drying trend -- since the expansion of the subtropical deserts is in fact a major prediction of climate change (see here, page 10-11).

THE FEEDBACK: Greenhouse gases cause climate change that increases drought and water shortages, which in turn drives countries to desalination, which in turn generates more greenhouse gases -- a classic amplifying feedback. A classic amplifying feedback unless, of course, you do the desalination with renewable power:

Some governments have countered or appeased those arguments by building wind farms to offset the power needs of their desalination plants. In Queensland, Premier Anna Bligh has challenged energy companies to come up with the best way to power a planned desal plant at Tugun on the Gold Coast using only renewable sources.

She said recently: "I want industry to come to us with their best ideas -- it could be solar or wind-generated power for example, it could be carbon offsetting, or it could be a combination. Making the plant carbon neutral will save 207,000 tonnes of greenhouse gas emissions every year -- which is equivalent to emissions from 46,000 cars."

Western Australia was first off the mark with a large-scale plant. Its Kwinana plant opened in November 2007. Now it provides about 45 gigalitres of water per year, about 17 per cent of Perth' s needs. It is powered by a wind farm at Emu Downs, although the Australian Competition and Consumer Commission recently found that statements by the Perth Water Corporation that the plant was carbon neutral were misleading, and told it not to make similar claims in the future. The corporation is now calling for tenders for a new plant at Binningup, 155km south of Perth.

Gosh, claims of carbon neutrality that were misleading -- who ever would have guessed? (see "CCX sells rip-offsets: "It seemed a little suspicious that we could get money for doing nothing"")

Victoria is building a plant at Wonthaggi in Gippsland which will supply about 150 billion litres a year, roughly one third of Melbourne's water. The Victorian Government says it has already included the price of using renewable energy into the cost of the project.

Sydney's desalination plant is being built at Kurnell on Botany Bay. The state government hopes to have it pumping 90 gigalitres of potable water per year from late 2009. To offset the power needs the state is building, with a private partner, a wind farm at Bungendore, east of Canberra. The 63-turbine farm is projected to have a capacity of 132 megawatts, about eight times greater than NSW's existing installed and accredited wind power.

Stung by public criticism of the plant's power needs, the state government says that renewable energy certificates earned from the wind farm will provide clear public evidence that the desalination plant is powered by 100 per cent renewable energy.

Running desalination plants on wind power is a start. But the future is using concentrated solar thermal power (CSP) for desal, see for instance, here and here. Given that Australia is one of the leaders in solar baseload, I suspect this will be their strategy once CSP becomes standardized over the next few years -- assuming people figure out what to do with the "super-salty brine" left over from desal:

Not everyone is happy with desalination. Community groups have sprung up in each state where a plant is planned to oppose them on environmental and finance grounds.

In South Australia, the Save Our Gulf Coalition says the planned plant at Port Stanvac presents many problems. Coalition chairman Peter Laffan says for one, the site is a contaminated former oil refinery.

"Our chief concern is the brine in the Gulf St Vincent because it is very slow moving water and we have unusual phenomena in dodge tides; every two weeks there is no tidal movements for a day or so."

That, together with the fact that flushing takes three to six months, means there is a significant threat that the brine will not disperse. Laffan says brine builds up in low-oxygen slugs that can create "dead" zones.

That's all we need -- more hot, acidic, and now salty coastal dead zones in a globally warmed future (see "The Dead Zone"). Such are the pitfalls of adaptation/desalination.

Maybe we should focus harder on prevention -- after all, it's going to take all the wind and solar (and other forms of carbon free energy) we can imagine just to avert mass desertification in the first place (see "Is 450 ppm (or less) politically possible? Part 2: The Solution").