Untangling controversy: Weather manipulation blamed in Sydney

False claims of ‘weather manipulation’ have arisen on social media as the cause of the latest bout of severe flooding in Sydney.

Claims have surfaced after the fourth major flood event in less than two years has hit Sydney.

Whilst an unusual amount of rainfall, the flooding is a result of a low pressure system skirting along the east coast of Australia, rather than weather manipulation.

It delivered a deluge of rain, with many areas receiving more rain in just a few days, than they would in an entire year. In Sydney, around 250mm of rain fell over three days, and in parts of the Illawarra, an astonishing 700mm of rain fell.

The system carried a substantial amount of moisture, due to the unseasonable warmth of the surrounding waters, which consequently elevated rainfall totals.

Off the coast of the Illawarra, temperatures were 2-3C above normal, which means more energy to fuel low pressure systems.

In addition to this, the natural phenomenon of La Niña has also exacerbated rainfall over much of the Australian continent.

Strong trade winds push warmer surface water and air into the western Pacific, enhancing rainfall and subsequent ground saturation in Australia, particularly in the east.

This, coupled with the low pressure system that swept through, led to the significant amounts of rainfall and subsequent flooding. However, controversy around its cause still exists.

People are taking to social media to falsify the explanations, and blame the floods on ‘weather manipulation’, after seeing a mixture of contrails and cirrus clouds in the sky, wrongly claiming it as cloud seeding.

Cloud seeding is a type of weather modification that involves sowing already sizeable clouds (rather than fair weather cirrus) with small particles released from an aircraft, to induce precipitation.

This technique has been in circulation for decades, and whilst controversial, can be particularly beneficial for those in drought-ridden countries that rely on precipitation for food production and farming.

Cloud seeding does locally occur in certain parts of the world, but is not widespread, nor used as a weapon against people to create severe weather events, such as the floods in Australia.

The same area of low pressure then pushed eastwards, with heavy rain also bearing down on parts of New Zealand.

The floods in Australia were a consequence of this large-scale weather system, coupled with the natural climate phenomenon of La Niña, which consequently elevated the severity of the event.