What winter? Lingering La Niña means no relief in sight for sweaty eastern Queensland

17 May 2022

La Niña climate conditions have already delivered a devastating summer for flood-ravaged Queensland and New South Wales' and the warm' wet weather won't let up anytime soon' a CQUniversity climate expert has warned.

CQUniversity Adjunct Professor of Environmental Geography Steve Turton says warmer ocean temperatures are driving unseasonable conditions for the Sunshine State.

"Right along eastern Queensland' all the way down from Cooktown' stronger trade winds will continue to bring in moisture' meaning warmer than average nights and higher than average humidity – possibly for the whole of what should be the winter season'" Prof Turton explained.

It was way back in late November that the Australian Bureau of Meteorology (BOM) declared the current La Niña' and forecast above average rainfall across much of northern and eastern Australia across the summer.

While Monday 23 May will mark six months of La Niña' it's unclear how much longer the climate event will last.

La Niña is caused by equatorial trade winds becoming stronger' changing ocean surface currents and piling up warm surface waters in the western Pacific and to the north of Australia.

Professor Turton' whose new book is titled Surviving the Climate Crisis: Australian Perspectives and Solutions' says that can mean more big rains well into winter.

"Notably' the wettest years on record for Australia occurred during the strong 1973-74 and 2010-12 La Niña events and were associated with this type of atmosphere-ocean setup'" he said.

"The increased heat and moisture in the western Pacific associated with La Niña usually means above-average winter-spring rainfall for Australia' particularly in the east and north.

"Also' the current negative Indian Ocean Dipole' or the difference in sea surface temperature between two poles' is contributing to extra heat and moisture from the southeast Indian Ocean that will shift west to east in the upper westerly winds - so we still have potentially months ahead of big rain events."

According to BOM (2021)' the six wettest winter-spring periods on record for eastern Australia occurred during known La Niña years.

Prof Turton said that traditionally the presence of La Niña also means cooler-than-normal top temperatures' but warned the trend may be shifting due to increased ocean temperatures – with Australian oceans warming more than 1° C since 1900.

Of the 18 La Ni̱a events since 1900 (including multi-year events)' 12 have resulted in floods for some parts of Australia Рbut Prof Turton said that was less likely in winter.

"Many of those La Niña flooding events have been due to the increase in tropical cyclone activity' which are almost entirely formed in the warmer months'" he said.

While the BOM has predicted the La Niña would break by late autumn or early spring' the US National Weather Service's Climate Prediction Centre and Columbia University's International Research Institute for Climate and Society have warned of a 59 per cent chance that it could continue through the Southern Hemisphere's winter and a 50 per cent chance of persisting thorough the Southern Hemisphere's spring.

Surviving the Climate Crisis: Australian Perspectives and Solutions will be available from CRC Press' Taylor & Francis (London' UK) in July 2022.