Under the conservative prime minister Scott Morrison, the government has yet to strengthen its climate pledge under the 2015 Paris agreement, as many nations have done in the past year. Morrison has personally ruled out committing to net-zero emissions. Pushing for a technological fix to global warming without moving to aggressively curb greenhouse gases is “sheer lunacy”, says Peter Frumhoff, chief climate scientist for the Union of Concerned Scientists, an advocacy group in Cambridge, Massachusetts.

From Wikipedia (https://en.wikipedia.org/wiki/Scott_Morrison):

The 2020 Climate Change Performance Index ranked Australia in last place for its climate policies and was the only country to score 0 for the same metric in 2021.

During the 2019–20 Australian bushfire season, Morrison dismissed suggestions of a link between Australia's emissions or policies and the intensity of the bushfires and initially downplayed the influence of climate change on the fires, but later admitted that climate change may have contributed.

Morrison declined to set net-zero emissions or other climate change targets, unlike other world leaders. Morrison allegedly requested climate change policy targets be removed from a proposed 2021 Australia–United Kingdom trade deal and initially suggested he would not attend the 2021 United Nations Climate Change Conference, but later confirmed that he would.

Morrison's government pledged that Australia would aim to achieve net zero emissions by 2050, but did not introduce this into national law; Morrison said he believed market forces and not government regulation can address climate change.

His government's climate action plan has been criticised as "lightweight", "meaningless", and a "mockery" that contains "no policy or strategy whatsoever".

Market forces, sure.

How much CO2 is emitted by those boats with their high-powered water pumps? How much noise is injected into the water body when these vessels operate in numbers day in, day out? How many vessels and hours of operation will be needed to have a cooling effect? Where do the clouds, where does the water go once it is vaporized and left drifting?

Come to think of it one could imagine to suck huge quantities of marine water to vaporize it and let it drift as clouds over land; thinking in the abstract, that could contribute to more shade, lower temperatures and more precipitation over hot and arid areas, thereby improving conditions for plants, animals, and humans. But, and this is a big one: how much energy will this need? How is that energy produced? How much water would one have to evaporate? What are the consequences for marine life? What are the consequences when the next government decides to cut funding? And what about the salt content of the aerosol, for certainly it will be utterly uneconomic to desalinate the water prior to spraying it?

My hunch is that those figures won't work out and that artificial clouds over the Great Barrier Reef also won't work out. The reef is called great because it covers an area of ~344,400km², roughly the area of countries like Finland, Congo, Germany, or Japan. According to the USGS[1], the water in a cloud with a volume of 1km³ weighs about 500,000kg. A 1m thick cloud layer over said area has a volume of 344.400km³ if I'm not mistaken, so weighs around 172,200,000kg. So in order to work one would think it to be requisite to spray in the order of a hundred million kg of water like almost daily into the air from seagoing vessels. There's an almost constant wind over most of the oceans so low-faring clouds will disperse in a matter of minutes or hours; the clouds however would be most desperately needed around noon each day which complicates things. Perhaps one could move the ships to upwind locations each day so clouds generated in the afternoon and the night get a chance to drift over the reef.

But imagine to do that for a country-size area: You'd need a fleet of tens or hundreds of thousands of not-so-small vessels. I cannot imagine photovoltaics to be a sufficient source of energy (for one, space is very limited on any vessel, and ironically, the vessel's reason for being there is to reduce impact of solar power). You'd need nuclear or hydrogen because otherwise you'd have to burn through untold tons of fossil fuels.

At any rate, the waters will not be calm anymore. The noise of the evaporators and the propellers will be deafening in the air and in the sea.

All told, a badly thought-out publicity stunt.

[1] https://www.usgs.gov/special-topics/water-science-school/sci...