麻豆淫院

(麻豆淫院Org.com) -- El Ni帽o and La Ni帽a 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.

鈥淎s the world continues to warm New Zealand is likely to experience the impacts of El Ni帽o and La Ni帽o events with comparable intensity and frequency to what we have seen over the last three decades, and possibly more so,鈥� says lead researcher Dr Anthony Fowler from the School of Environment. 鈥淭his means that we should anticipate more extreme events, such as flooding and droughts, in the regions affected by these weather patterns.鈥�

In New Zealand, El Ni帽o 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 Ni帽as. 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.

鈥淭he El Ni帽o / La Ni帽a phenomenon has been referred to as the heartbeat of the world,鈥� Dr Fowler says. 鈥淎fter the seasonal cycle and monsoons, it鈥檚 the most important source of year-on-year climate variation. Strong events often cause incredible damage and affect hundreds of millions of people around the world. El Ni帽os, in particular, have been responsible for some of the devastating 20th century droughts in Australian, floods in South America, and failure of the monsoons in India.鈥�

鈥淭o date the global climate models used to 鈥檖redict鈥� the future have been unable to give us a clear picture of what will happen with El Ni帽o and La Ni帽a as the world warms,鈥� he says. 鈥淏ut understanding the phenomenon is critical to learning what climate change will mean for the world鈥檚 population.鈥�

鈥淭he premise of our work is that we know that the world has warmed over the last few centuries and we can look back to see what has happened with El Ni帽o / La Ni帽a over that time. By studying how the phenomenon has behaved in the past we can anticipate what might plausibly happen in the future. This should result in more informed scenarios of future regional climate change.鈥�

The scientists studied the climate record in kauri tree rings dating back to AD 1300. 鈥淜auri trees are quite sensitive to these weather patterns,鈥� Dr Fowler explains. 鈥淒uring El Ni帽o events they grow rapidly and have wide tree rings whereas during La Ni帽a events they grow more slowly and have narrow rings.鈥� The rings can be accurately dated, providing a detailed record of when El Ni帽o and La Ni帽a events have occurred.

"Notably wide and narrow kauri tree rings have become more frequent as the world has warmed over the last few centuries. We infer from this that El Ni帽o and La Ni帽a events become more frequent or intense as the world warms, or that New Zealand's climate becomes more strongly influenced by such events. Either possibility suggests that droughts and floods related to El Ni帽os and La Ni帽as will continue to significantly affect New Zealand, and may well become more intense.鈥�

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. 鈥淜auri logging in the 19th and early 20th century devastated the landscape,鈥� he says. 鈥淏ut a lot of the wood that was cut down can still be found in the weatherboards of our houses and provided important data for our research.鈥�

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 Ni帽o / La Ni帽a activity in the 20th century is the most intense ever seen 鈥� as suggested by currently available records 鈥� or a return to conditions that have occurred in the past.