Scientists unpick Australia's year of weather disasters

While the east coast was awash with water, plenty of other events were happening including extreme heat in the west and the Antarctic, as well as wild winds and hail storms.

Here's a look at some of the events examined in the State of Climate and Weather Extremes 2022 report.

The expert authors, from the Australian Research Council Centre of Excellence for Climate Extremes, hope it will help governments and the public understand the complexity and nature of the climate extremes being witnessed.

DEVASTATING FLOODS IN QLD AND NSW:

The northern NSW town of Lismore was the face of devastating series of storms that flooded southeast Queensland and NSW in the first half of 2022.

Rainfall records were smashed, with some regions experiencing more than five times what they'd normally get in a month. It was the costliest flood in Australia's history, with more than 20 lives lost.

In Lismore, flood waters surged two metres above the previous record, forcing families onto rooftops to survive.

Scientists say the floods resulted from a combination of meteorological phenomena.

First, the La Nina weather pattern meant catchments were already sodden and primed for flooding.

Then, in late February, a Rossby wave triggered the development of multiple rain-producing weather systems.

Rossby waves are building blocks of weather and are high-altitude, planetary-scale waves that largely drive a range of weather at the surface level, according to the report.

They are disturbances in planetary waves, such as the jet stream over Australia.

As the waves get bigger, they can break, just like at the beach.

A Rossby wave breaking event, south of Australia, was one of the main drivers of the weather that inundated so much of Queensland and NSW in February and March.

SYDNEY'S WETTEST YEAR:

Just three weather events delivered almost half of the staggering amount of rain Sydney copped in 2022.

The city's wettest year on record saw 2530mm fall - more than double the average.

Atmospheric rivers - which work like conveyer belts and deliver relentless streams of moisture-laden air from the warm Coral Sea - and east coast lows were largely to blame.

Three events - in February/March, July and October - were responsible for 40 per cent of the rain. The result was flash flooding across Sydney, significant flooding of the Hawkesbury-Nepean catchment, and forced the evacuation of 85,000 people.

A recent study by the ARC Centre of Excellence suggests the number of atmospheric rivers may increase by 80 per cent by the end of the century under moderate and high emissions scenarios.

RECORD HEAT IN WA:

A complicated mix of weather events saw heat records fall in Western Australia in the summer of 2021-22.

In January, a strong high-pressure system over the Great Australian Bight brought hot, dry weather from the desert to Perth as a coastal trough blocked sea breezes.

The result was six consecutive days above 40C in Perth - the longest such run for any month in 123 years of observations.

The Pilbara region also endured a record-breaking heatwave, with the town of Onslow equalling Australia's hottest day on record when the mercury hit 50.7C on January 13.

The previous month, suppressed tropical activity saw Marble Bar, also in the Pilbara, briefly become the hottest place on the planet, reaching 46.2C.

Heatwaves are now one of the most deadly natural hazards in Australia and they are expected to continue to worsen as the climate warms.

ANTARCTICA FEELS THE HEAT:

Last year was one of record sea ice loss and record heat in Antarctica.

In March, a heatwave hit resulting in temperatures over 50C above average in some areas.

The same month also saw the collapse of part of the East Antarctic ice shelf the size of New York City, with the heat also driving the collapse of the Conger ice shelf.

The Antarctic also broke records for loss of sea ice in 2022 and that has continued, with sea ice extent falling to a record low in 2023.

The 2023 Antarctic sea ice minimum extent was about 40 per cent less than the average between 1981 and 2010.

That's alarming because Antarctic sea ice reflects sunlight and influences air-sea interactions and ocean circulation, and is an important habitat for krill, which underpins the Southern Ocean food web.

Sea ice also holds Antarctic ice shelves in place, something that helps ward off sea level rise.

WILD WINDS IN A DAY OF DOUBLE TROUBLE:

On the same day last November, severe thunderstorms lashed parts of South Australia and the Northern Territory, leaving trails of damage.

The storms were part of a broad region of severe weather that extended through central Australia, and while both produced severe winds they were very different.

Adelaide was hit by a line of storms that stretched for 140km, producing gusts of more than 100km/h, causing transmission lines to fail and cutting off the state from the national grid.

In Alice Springs, roofs were lost to a single storm that was 10km wide and produced a microburst - a strong wind event common over regions that have a deep layer of hot, dry air near the surface.

Scientists say more research is necessary to ascertain how climate change will impact events like these in the future.

HAIL HAMMERS THREE STATES:

Destructive hail storms hit Victoria, Queensland, and NSW last year and farmers, in particular, copped a belting.

In the first couple of weeks of 2022, large hail caused widespread damage to potato crops in Victoria and citrus and grape crops in NSW. Some grape growers lost half their crops.

In October, near Rockhampton in Queensland hail the size of cricket balls fell.

The following month hailstorms tore across Victoria's Mallee region, leaving millions of dollars in crop and property losses. Port Macquarie was also pelted causing significant property damage.

Climate change affects atmospheric properties associated with hail.

Experts believe hailstorms might be less frequent but more severe as the climate warms, but also warn the effect on hail remains highly uncertain.