Despite warmer temperatures in many places, El Niño is expected to be a bit milder and drier in New Zealand. Photo: 123RF
A climate scientist says the developing El Niño weather-pattern is likely to have a better effect on this country than in many others.
El Niño is caused by warm water rising to the surface in the western Pacific, pushing heat into the atmosphere.
It is expected to linger for about 18 months and is likely to mean drier conditions in the north and east of both the North and South Islands with more rain than usual in western areas.
Kevin Trenberth, a distinguished scholar from the National Centre for Atmospheric Research in Colorado and a former Auckland University academic, said New Zealand is one of the few places in the world that becomes cooler in an El Niño.
''In some ways it is a good thing for New Zealand. Last year was the warmest year of record for New Zealand, that's La Niña.
"In El Niño conditions New Zealand tends to cool off a little bit. We tend to get more westerly flow or even south-westerly flow, especially in June and July.
"So we get rid of a lot of these sub-tropical lows that have been bringing all of this moisture down.
''Rain bomb in Auckland and a tremendous amount of water all around the North Island, meanwhile the South Island was relatively sunny over the first three months of the year, and so those kind of conditions are likely to change quite substantially.''
He said there is more likelihood of fronts and rainstorms coming in from the west.
''So the West Coast is certainly likely to continue to get wet conditions or maybe a return to wet conditions as it has been relatively dry there for the last year.
''I would say improved general conditions for the general public at least in the North Island.
''El Niño conditions tend to pull most of the activity away from New Zealand further to the east, so New Zealand is usually in somewhat more benign conditions I would say.''
Trenberth said El Niño could also mean a greater risk of bushfires in Australia over the summer with the chance of smoke reaching this country as happened in 2019-2020.
''Maybe a little bit like the kind they are experiencing in the US with regard to the wildfires in Canada.''
He said if smoke gets into the lower stratosphere it can hang about for several months and affect the weather.
Trenberth said droughts in parts of New Zealand is also a possibility.
''That's the thing to watch out for next summer.''
''Droughts in New Zealand are or should be reasonably be manageable. They are not that long-lived, and we are surrounded by water. It's not the kind of conditions that you get in Australia or Canada or California for instance."
Trenberth said that generally the consequences of El Niño are getting greater because of global warming and sea temperatures are inevitably higher.
''With El Niño around the world there tends to be more dry conditions, even droughts, which is one of the things that raises temperatures overall. 2024 is looking like to be a substantial jump in the global mean surface temperature.
"Even 2023 could well become the warmest year of record.''
He said sea temperatures globally are about 0.3C higher than any other year on record including 2022 which was fairly warm.
''In large part that's because of the warming in the tropical Pacific that is already occurring. The signals are, look out really.''
Trenberth said El Niño is something worth watching pretty closely.
''There are apt to be some substantial consequences in various places around the world.
"The risk of drought and wildfire in South-East Asia and Indonesia grows and there are consequences in South America and in Africa. It has impacts downstream on things like cholera and other diseases.
"I would say, watch this space because there will be other links to El Niño that are worth looking at that hopefully, at least from our standpoint will occur elsewhere.''