NZ scientists warn 'more extreme rainfall in warming world'

Flooding continues to block roads in Kaipara Flats in Auckland's north on January 30, 2023 in Auckland, New Zealand. (Photo: CFP)

AUCKLAND, Jan. 31 (Xinhua) -- With the maximum amount of water vapor in the air increasing exponentially with temperature, the potential for extreme rainfalls grows as the climate warms, New Zealand scientists warned on Tuesday.

Auckland is currently challenging the record for its wettest month ever. More than 769 percent of its rainfall in a normal January has been recorded so far, which was about more than a third of Auckland's entire annual average, with further round of downpours likely to hit again on Tuesday night.

"Not that every storm brings a deluge, but as we warm the climate, we constantly weight the dice towards heavier rainfall events," Prof. James Renwick from Victoria University of Wellington explained the link between a warming climate and such extreme rains.

Record rainfall from Friday morning through overnight to Saturday morning in Auckland caused massive flooding across the biggest city in New Zealand.

New Zealand Prime Minister Chris Hipkins said the severe weather was a climate change.

"When the rain hit, it hit very hard and very fast... Aucklanders need to brace for the fact there could be more rain. This is quite unprecedented," Hipkins said.

The country's national meteorological service MetService issued Red Heavy Rain Warning for the Auckland area overnight and recorded 249 mm of rain in 24 hours until 1 a.m. Saturday.

The previous 24-hour record of rainfall was 161.8 mm, dating back to February 1985, according to MetService. The red warnings are only issued for the most significant weather events.

The record rainfall has caused massive flooding to houses and properties, claiming four people's lives and forcing the closure of state highways and the Auckland Airport, with the state of emergency declared by the government.

Prof. Renwick said many of the heaviest rainfall events in New Zealand and elsewhere are associated with "atmospheric rivers" which means vast corridors of moisture that extend from the tropics to higher latitudes. The recent flooding in Auckland is an example of this.

As the atmosphere becomes more loaded with water vapor, these "rivers" are set to transport more moisture. Already, a significant atmospheric river carries as much water as the Amazon does, he said.

Dr. Daniel Kingston of the School of Geography, University of Otago, said the Auckland catastrophe was linked to atmospheric rivers funneling warm moist air down from the tropics, and its relatively slow passage over the country -- similar to the slow-moving atmospheric river that devastated the top of the South Island in August last year.