요즘들어 부쩍 일기예보가 맞지 않는 일들이 잦아지고 있습니다.
하루하루 날씨에 대한 이야기 보다는 계절 전체를 놓고 봤을 때 '기후 변화'가 급격히 일어나고 있음을 이야기 하는 말입니다.
뉴질랜드 생활 3년이 되가면서 격었던 봄 여름 가을 겨울 12번이 모두 약간 비슷하기는 했지만 적응하기에는 어려웠던 점을 생각해 그 변화가 범상치 않음을 느끼게 됩니다.
몇일 전에 뉴스가 하나 실렸습니다.
카우리 나무를 연구하고 있는 오클랜드 대학교 과학자들의 발표에 의하면 카우리 나무의 나이테를 연구하면서 1천년 이상된 카우리 나무의 나이테를 통해서 뉴질랜드 기후변화 역사를 알아내고 있다고 합니다.
과학자들에 따르면 뉴질랜드도 엘리뇨와 라니냐 현상의 영향을 지속적으로 받아왔는데, 엘니뇨 현상 속에서 는 카우리의 나이테가 큰폭으로 나타나고, 라니냐 현상에서는 좁고 촘촘한 경향성을 발견했습니다. 이같은 사실에 기초해서 뉴질랜드 기후가 지난 1천년동안 어떻게 변화 해왔으며 앞으로 어떻게 변화 할 것인지를 알 수 있게 된것입니다.
물론 '안다'는 것이 정확한 예측을 기대하기는 어렵겠습니다만, 어느정도 예측을 할 수 있다는 이야기 같습니다.
엘니뇨와 라니냐 현상을 뉴질랜드에 들이대보면,
과학자들은 엘니뇨에서는 추운 남서풍에 가뭄이 들게 되고, 라니냐 현상에서는 덥고 비가 많이 내리게 된다는 결론을 내렸습니다. 그리고 뉴질랜드 날씨가 더욱 극단적인 변화를 격게 될 것으로 전망했습니다.
일정한 주기를 가졌던 엘니뇨와 라니냐 현상이 급격히 번갈아 가면서 뉴질랜드를 엄습하게 된다는 설명입니다.
뉴질랜드가 최근 수년동안 여름에도 비가 많이 오고, 겨울에도 열대성 폭우가 내리는 이상 기후를 보이고 있는 것은 카우리 나무의 나이테 관찰로 설명이 가능하다고 합니다.
지난 2011년 말과 올해 초를 돌아 보면
북섬에서는 계속되는 비와 강한 바람으로 전형적인 여름을 전혀 느낄 수 없었습니다. 또한 남섬은 가뭄으로 경제가 큰 타격을 받기도 했습니다.
지금 보내고 있는 겨울도 기후는 전과 같은 양상을 보이는 것이 아니라 시도 때도 없이 비가 내리고 그 형태가 마치 열대성 폭우를 연상케 하고 있습니다.
평균 기온 또한 내려가서 오클랜드는 겨울에 대체적으로 온화한 기온을 보였는데 몇일전에는 차창에 얼음이 얼어 있을 정도로 기온이 내려가는것을 경험하고 있습니다.
... ...
급격한 기후 변화에 어떤 준비를 해야할까요?
... ...
[라니냐 & 엘니뇨 현상]
동태평양의 해수면 온도가 5개월 이상 평년보다 낮아지는 경우를 말한다.
이렇게 차가워진 동태평양의 바닷물은 여러 기상이변을 일으킵니다.
대표적인 기상이변으로는 동태평양에 위치한 페루를 비롯한 여러 지역에 심함 가뭄이 들고 북미 등지에는 강추위가 몰아치게 됩니다.
반대로 서태평양에 위치한 동남아시아는 장마가 발생하게 됩니다. 뉴질래드가 서태평양 남단에 위치한 관계로 극심한 홍수는 없을 지라도 때에 따라서 폭우가 내리게 됩니다.
지난 2012년 여름 엄청난 비가 내리고 일부지역에서 홍수로 인한 재난이 발생한 것이 이 라니냐 현상 때문이라고 할 수 있습니다.
엘니뇨 현상은 라니냐와 반대이므로 엘니뇨 현상이 일어날 경우 서태평양에 위치한 호주와 뉴질랜드는 홍수가 아니라 가뭄 피해가 발생하게 됩니다.
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참고기사1.
Tree-ring anomaly mystifies scientists
The last part of Eloise Gibson's series talking to climate experts about what they don't know, what they wish they knew and how they can find out more.
Scientists are chipping away at a glitch in the climate records, hoping to explain why tree-rings that track temperature changes successfully until the 1950s suddenly veer off.
Researchers believe global warming or other man-made changes may be to blame for an unexplained slowdown in growth of some of the ancient trees used to track temperatures back more than 1000 years.
Although tree-rings records appear to be a good measure of temperature changes most of the time, nobody knows why the usual techniques used with them fail from the 1960s.
The divergence between tree-rings and real, thermometer measurements in the past 50 years has been used to attack temperature reconstructions used by the International Panel on Climate Change and others - particularly since emails from the University of East Anglia's climatic research unit revealed unit head Phil Jones discussing "hiding the decline" in tree-ring temperatures.
It turned out the email referred to a common technique of replacing tree-ring records with direct thermometer measurements from 1961, when tree-rings show temperature declining while real measurements from thermometers do not.
But although researchers of ancient climate have several theories, so far no single theory can explain why some Northern Hemisphere trees behaved differently in the past few decades.
Dr Andy Reisinger, a climate researcher at Victoria University who has followed the progress of proxy temperature reconstructions, said it could be that a lack of rain in recent decades had stunted tree growth in some high-altitude spots - or that when temperatures reached a certain point, trees began to react differently.
Whatever the cause, "the relationships [between tree-rings and temperature] that we've developed for the last 500-100 years may not apply in the last 50," he said.
So far, Dr Reisinger said tree-ring records from the Southern Hemisphere were limited.
"Tree-rings always only tell you something about a specific location and therefore tree-rings are always selective," he said.
Tree-ring records study the width of tree-rings - the wider the ring, the more the tree grew that year.
Generally trees grow more in warmer years.
Tree-ring records are often combined with other ancient reconstructions to form a "hockey stick" pattern, which shows late 20th century temperatures rising sharply from the long-term average.
Those reconstructions helped the IPCC conclude that the last 50 years of the 20th century were probably the warmest in the Northern Hemisphere in more than 1000 years.
Dr Reisinger said that for most of the record tree rings match other physical evidence from ice cores, sediment records, stalagmite and coral fairly closely.
There is no way of confirming the picture with real thermometer temperatures until 1850, although tree-rings are fairly accurate for most of the period when thermometers overlap.
Meanwhile, New Zealand researchers at Auckland University and the National Institute of Water and Atmospheric Research, including tree-ring specialist Andrew Lorrey, may be able to add to the picture by building a long-term climate record from Kauri stumps many thousands of years old.
Massive kauri trees found buried in Northland bogs have yielded some of the world's oldest tree-ring records - some about 30,000 to 60,000 years old.
Some kauri rings are already being used to build a partial record of droughts.
참고기사 2.
기사원문 : http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10783688
Say goodbye to the classic Kiwi summer
More floods, droughts and extreme weather events associated with the El Nino and La Nina cycles can be expected in New Zealand in a warming world, Auckland researchers predict.
A group of University of Auckland scientists looking at 700 years of climate records found that El Nino and La Nina cycles "ramped up", or became more common as air and sea temperatures rose.
Their findings are published today in the journal Nature Climate Change.
Lead researcher Anthony Fowler said many large El Ninos and La Ninas had occurred with greater frequency in the past 30 years.
His team's study suggested that this trend might not be in isolation, but a sign of things to come.
"As the world continues to warm, New Zealand is likely to experience the impacts of El Nino and La Nina events with comparable intensity and frequency to what we have seen over the last three decades, and possibly more so," Dr Fowler said.
"This means that we should anticipate more extreme events, such as flooding and droughts, in the regions affected by these weather patterns."
Article continues below
His team created a climate record for every year since AD1300 by studying kauri tree rings.
Kauri are highly sensitive to the ebb and flow of the cycles, with wide growth rings in their trunks often associated with the cool, dry El Ninos and narrow rings with rainy La Nina patterns.
The scientists previously created a 300-year-old record by studying the rings in living trees. To go further back in time, the group collected ring samples from logged wood, and colonial-era buildings - a burned-down church in the Bay of Islands, weatherboard homes and display pieces in museums.
By looking at how the rings widened and thinned as the world warmed over several centuries, the researchers learned how La Ninas and El Ninos behaved over this time.
These results allowed them to anticipate what might happen to our climate in future, Dr Fowler said.
"If I was talking to water resource planners, I would be suggesting that they might want to start to think about the possibility of more extreme or more frequent El Ninos.
"I can't say I can predict it, but it's a plausible possibility given what has been observed in the past."
Dr Fowler acknowledged it was ironic that the studies benefited from environmental destruction - the piecing together of the climate record was mainly possible because of devastating logging of kauri in the 19th and early 20th centuries.
STORM CHILDREN
The weather cycles known as El Nino and La Nina - Spanish for the boy and the girl - have the greatest influence on our climate after the seasons and monsoons, and have been responsible for devastating floods in the past three years in Pakistan and Australia.
The weather cycles were first noticed by Peruvian fishermen - hence their Spanish names. When anchovy stocks fell in the 1700s, that was blamed on a strange, warm current in the eastern Pacific. The event was named El Nino, "the boy child", because it arrived at Christmas.
El Nino (The boy child)
In New Zealand, El Nino generates cool southwesterly winds and is associated with droughts on the eastern sides of both islands.
La Nina (The little girl)
La Nina - which New Zealand has experienced this summer and last - brings wetter, warmer conditions, greater rainfall and sometimes floods.
By Isaac Davison | Email Isaac