The FINANCIAL -- El Niño and La Niña weather patterns will become even more dominant in New Zealand with climate change, according to research from The University of Auckland published in Nature Climate Change.

According to The University of Auckland, in New Zealand, El Niño events usually bring more cool south-westerly winds. The whole country tends to be relatively cool with associated droughts in sheltered eastern areas of both islands. The winds reverse with La Niñas. Moisture laden air from the sub tropics elevates temperatures, especially in the North Island, and brings higher rainfall to much of the country, sometimes with associated floods.

The scientists studied the climate record in kauri tree rings dating back to AD 1300. “Kauri trees are quite sensitive to these weather patterns,” Dr Fowler explains. “During El Niño events they grow rapidly and have wide tree rings whereas during La Niña events they grow more slowly and have narrow rings.” The rings can be accurately dated, providing a detailed record of when El Niño and La Niña events have occurred.

Dr Fowler says that stitching data together from living trees and logged wood, to create a continuous record of the last 700 years, was a significant achievement for the research team. He notes the irony in one form of environmental damage yielding clues about another.

The next phase of the research, which is almost complete, involves adding data from kauri trees preserved in swamps to extend the record back almost 4,000 years before present. This longer record may help to answer the outstanding question of whether the El Niño / La Niña activity in the 20th century is the most intense ever seen – as suggested by currently available records – or a return to conditions that have occurred in the past.

The current work was funded by the New Zealand Foundation for Research Science and Technology and a Marsden grant from the Royal Society of New Zealand.

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