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2014年7月14日星期一

El Nino: A wild card for planters


by Adrian Lim bizhive@theborneopost.com. Posted on July 13, 2014, Sunday
Weather, as one of the more important aspects for palm oil planters to worry about for their production during the year, is rapidly changing.
A sudden change in weather condition – especially dry and hot weather for a extended period – can negatively affect production and output of palm oil.
As one of the plantation experts Dorab Mistry said, the weather is expected to shape the production and price of the crude palm oil (CPO) this year.
“In the event that El Nino develops, I believe CPO futures will cling to RM3,000 beyond June.
“(Palm oil) production is likely to be affected from late 2014 onwards and we may be staring (at) RM3,500.
“However if rains come as normal and the high cycle kicks in from July onwards, prices can trade in a range between RM2,900 and RM2,600 from July until October.
“Palm oil production is under-performing and stocks are tight,” he said during a palm oil conference in Kuala Lumpur earlier this year.
At the same time, Mistry highlighted some new developments within the oil palm industry which could steer the palm oil market into a new dynamic cycle.
“There is going to be a big expansion of bio diesel capacity in Indonesia in the near future.
“This capacity will require bio diesel producers to lock in palm oil prices at least one year in advance. Almost all of them will be plantation linked.
“Hence, the availability of freely tradable palm oil will become somewhat restricted. It will also require much larger stocks to be maintained.
“Therefore, palm oil stocks will need to be much larger before they begin to exert any pressure on prices.
“For these reasons, I believe the Indonesian mandate is truly a ‘Game Changer’ and will keep palm oil prices relatively high for a long time,” Mistry observed.
On the contrary, he believed there is a small likelihood of production surpassing expectation if rainfall is better than normal.
“If prices of Brent (crude oil) fall and production of world oilseeds is also as expected, palm oil prices can fall below RM2,400 but that possibility is no more than 30 per cent,” he pointed out.
While Mistry, a director of India-based Godrej International Ltd, has his own view on the palm oil market, local analysts hinted at a similar scenario, citing  change in weather conditions and palm oil inventory level being the prime aspects affecting the outlook of the plantation industry.
M&A Securities Sdn Bhd (M&A Securities) in a report dated June 26 entitled ‘Betting on El-Nino for palm oil price up-cycle’ said weather plays an important role in the supply equation of production and yield, and particularly one of the key catalysts of CPO price movement.
The hot and dry weather of late is expected to persist for another few months as predicted by the Malaysian Meteorlogical Department. The situation has cause caustic reaction as people wonder whether El-Nino spell had started or otherwise.
Citing the Department of Meteorlogical Malaysia, M&A Securities said the current situations are due to the Southwest Monsoon (dry season for Malaysia) that has started in May and is expected to persist until September.
Surveys by international weather forecasters still indicated that there is a 70 per cent likelihood of the El Nino happening in 2014.

Potential effect of El Nino on palm oil production
Plantation experts have estimated that El-Nino could potentially reduce production up to 30 per cent during normal time depending on severity.
As a result of lower production and lesser yield, the situation could cause the supply of  palm oil inventory to be tight.
Already languishing from lower exports and stocks level compared with last year, industry players are anticipating the dry weather to be a potential factor that could exert pressure on CPO price to trade higher.
Ling Ah Hong, a director of Malaysian plantation consultancy and investment company Ganling Sdn Bhd who shared his views during a palm oil conference, said El Nino is normally followed by a surge in palm oil prices due to disruption of supply.
He noted that historically, when El Nino develops, palm oil prices increase.
Outlining two scenarios, he explained a moderate El Nino will reduce global supply growth in 2015 to less than 0.5 million tonnes while a severe EL Nino will result in a contraction of 0.6 million tonnes, subsequently leading to severe supply tightness in the world.
Another factor which Ling strongly believed could cause CPO price to trend higher in the future, is the tightening supply of palm oil inventory.
Giving an outlook for CPO price, he indicated that the price could be moving higher next year.
“We expect palm oil prices to trend higher in 2014 and 2015. (The) average price for 2014 is expected to increase by about 14 per cent to RM2,700 per tonne against RM2,360 per tonne in 2013.
“This will be supported by steady demand from food and additional demand of two million tonnes from Indonesia domestic biodiesel usage.
“Looming palm oil supply tightness due to past and emerging dry weather will be a key catalyst to upward price movement in 2015.
“Plantation companies in Indonesia and Malaysia should generally fare better this year (compared with 2013),” he observed.
Ling also observed that Sabah and Sarawak planters should witness a recovery in production this year as both geographical locations have expereinced no prolonged rainfall deficit  in 2012 and 2013.
Whether rain or dry season is coming, analysts are cautious on the sector’s prospect at present.
Sector outlook and analysts top pick
Despite the possible occurance of the El-Nino, analysts have yet to call the shot of a “buy call” on the plantation sector.
Most of them are forecasting the sector to perform largely in line with expectations with an upward bias.
Malaysian Palm Oil Board (MPOB) which released the palm oil statistics for June on July 10 revealed that the palm oil inventory fell to one-year low.
The research arm of JF Apex Securities Bhd (JF Apex Research) in a report said despite going into high production season, CPO production was lower in June, down 5.26 per cent on monthly basis after growing 6.5 per cent in May.
It observed that the drop of CPO production in June was steeper than market expectations of 0.4 per cent decline as surveyed by a news agency.
JF Apex Research analyst Jessica Low said, “We reckon that the steep fall of palm oil inventory in June to one-year low is a positive surprise to the plantation sector and would support CPO prices.
“The CPO production was under pressure in June as a result of laggard effect of drought in January.
“Looking ahead, we expect CPO production in July to ease further before resuming its uptrend in August, as harvesting days will be fewer in July due to the Hari Raya festival.

“Meanwhile, spot CPO prices are moving around RM2,430 per metric tonne (MT), its nine-month low level.
“We feel that the current CPO price had factored in the adverse effect and expect limited downside for CPO prices,” she said.
For exposure to the plantation sector, most analysts believe that TSH Resources Bhd (TSH) is one of the best performing plantation companies throughout Malaysia.
They believed earnings of TSH is poised to grow healthily over the next few years supported by higher FFB production and better FFB yield on matured palm oil plantation.
The research arm of Public Investment Bank Bhd (Public Invest Research) in a report dated March 20 said TSH’s young Indonesian estates amidst the bullish CPO price movements will see the company become of the biggest plantation gainers this year.
The research firm even highlighted that the plantation company’s young  age profile of its oil palm plantation is the growth driver.
Public Invest Research said close to 78 per cent of TSH’s total planted are are below seven years old, with an average age of about six to seven years old.
“We believe the company will be able to maintain its double-digit fresh fruit bunches (FFB) production growth in the next couple of years, albeit at a slower pace driven by its young (tree) age profile.
“In addition, there is unplanted landbank of 23,815 hectares and 53,430 hectares in Malaysia and Indonesia respectively, pointing that there will be continuous expansion in the company for the next 10 to 15 years.
“In the next five to 10 years, we believe the company will rank on par with big capitalisation plantation companies once it has achieved sizeable mature area,” the research firm said.
In the meantime, Public Invest Research is expecting the company to register strong earnings growth this year.
The research firm had forecasted a strong jump for TSH group’s earnings this year supported by increases in palm oil production and CPO prices which will highly benefit the company in being a pure upstream plantation player.
Nonetheless, its forecasts are based on the assumption of 16 per cent rise in FFB production and full-year average CPO price of RM2,750 per metric ton, which is significantly stronger than the average CPO price of RM2,251 per MT recorded last year.
Following a visit to TSH’s plantation estate in Palangka Raya, Central Kalimantan earlier, PublicInvest Research said the company’s plantation estate, PT Sarana Prima Multi Niaga Estate in Central Kalimantan boasted a total gross area of 7,198 hectares.
The research firm said the plantation estate, equipped with a 45 metric tonne per hour mill is producing FFB for TSH and is also one of the best performing mills for the company with an average oil extraction rate (OER) of 24.6 per cent for the last three years.
Hence, given higher FFB production for TSH and its young age profile of the company’s oil palm plantation, Public Invest Research is optimistic that the plantation company earnings will be sustained in the near future.
At the same time, the research arm of Kenanga Investment Bank Bhd (Kenanga Research) and RHB Reseach Institute Sdn Bhd are both upbeat about the company’s financial performance for financial year 2014 (FY14).
Obviously, analysts are sounding the drum after TSH’s financial results for the first quarter of 2014 (1Q14) has largely beaten their expectations.
For 1Q14, TSH’s net profit jumped 162 per cent year-on-year (y-o-y) to RM52.17 million compared with RM19.93 million recorded in 1Q13.
RHB Research said the better than expected financial results was attributed to higher average CPO price realised and double-digit production growth.
Going forward, the research firm expects TSH’s new matured oil palm plantation in Kalimantan and improving FFB yield to lift its earnings for  upcoming quarters.
The research arm of MIDF Amanah Investment Bank Bhd (MIDF Research) also believed that the company’s long term growth remains strong supported by sizeable unplanted plantation landbank and new planting programme.
MIDF Research in a report dated May 23 said, “Given substantial portion of immature and young trees, we are optimistic on TSH long-term earnings prospect.
“TSH high proportion of immature and young trees will be the catalyst to support TSH’s earnings in the long-term.
“Furthermore, as at December 2013, about 66 per cent of its total plantation landbank is still unplanted.
“With new planting programme of approximately 3,000 hectares per year, we believe the growth story of TSH will remain intact,” the research firm noted.
As for Sarawak planters, most of them do not foresee the potential occurance of the El Nino to have an adverse impact on their production.

SARAWAKIAN PLANTERS OUTLOOK

Ta Ann
Ta Ann Holdings Bhd (Ta Ann) being one of the large capitalisation company listed on Bursa Malaysia does not foresee any adverse impact related to El Nino phenomenon as it implements good water management system to conserve water in its peat plantations.
Ta Ann group managing director was quoted as saying,”The potential occurance of the El Nino dry weather phenomenon will not have much impact on the oil palm sector in Sarawak.
“This is because more than 40 per cent of the state’s oil palm plantations are in peat soil areas.
“The water management in peat soil areas will continue to provide water for the palms.
“El Nino will have greater impact on those planted in mineral soil,” he said.
As for Ta Ann, the timber cum plantation company expects its FFB production for 2014 to be around 12 per cent to 14 per cent higher compared to last year as more plantation matures.
Looking ahead, the company expects to carry out new planting of around 2,000 hectares this year which mainly are expansion of its existing plantation estates.
When asked on the company’s plans to acquire more landbank in the near future, Ta Ann revealed plans to develop more native customary rights (NCR) lands jointly with native landowners which will bring many socio-economic benefits.
The company is still in discussions with relevant parties for more land acquisitions to further expand the company’s plantation division.
Additionally, Ta Ann is optimistic on the price of CPO in 2014, expecting comparatively stronger financial performance this year on the back of the anticipated higher FFB production and brighter price outlook for palm oil and timber.
Its young age tree profile with an average of seven years will contribute sustainable growth to the company’s earnings in the future.
The group’s oil palm estates are located in several districts throughout Sarawak, for instance in Sibu, Daro, Igan, Bintulu and Song.

Sarawak Oil Palms
Moving on to another plantation player, Sarawak Oil Palms Bhd (SOP) also expects the company’s FFB production to post double digit growth despite the probability of El Nino.
SOP said,”The FFB production for 2014 is expected to be 1.1 million MT, representing growth of 17.7 per cent against 2013 FFB production.
“The key factor for growth is the shift of palm age profile to more productive age profile despite current dry weather,” the company said.
SOP disclosed that as at Dec 2013, 50.9 per cent of the company’s palm age profile is young from four to 10 years old, 26.8 per cent has achieved prime age between 11 to 20 years, 12.7 per cent is immature and just about 9.6 per cent is 21 years and above.
Moving forward, the company said there will be some replanting of less than 500 hectares carried out at its plantation estates located along Lambir and Suai areas in Miri.
Majority of its plantation estates are located within Miri and Bintulu divisions and its estates located at Niah area has posted the higher yield per hectare for 2013.
As part of the group’s expansion plan, SOP recently announced an acquisition of two plantation companies with 9,600 planted hectares located at Sebauh, Bintulu.
The acquisition is currently pending the fulfillments of certain conditions.
As for CPO prices, the company expects it to move in the range of RM2,400 to RM2,500 per MT this year.
On SOP’s 2014 financial performance, the planter believed it should perform better than last year with improved FFB production and higher average CPO price realised this year as compared to 2013.

Rinbunan Sawit
Likewise, another plantation company Rimbunan Sawit Bhd (Rimbunan Sawit) concurred with Ta Ann and SOP that if the El Nino does happen, its production will not be substantially affected.
In an e-mail interview, Rimbunan Sawit managing director Tiong Chiong Ong expects its our overall figure to go up slightly despite an estimated drop of 10 to 20 per cent by (the potential occurance of)  El Nino effect because of increasing matured area and more palms reaching prime production age.
“Currently, the age profile of our oil palm plantation is mostly in the range of seven to 15 years.
“Out of a total of 54,670 hectares, 16,290 hectares or 30 per cent is in the range of seven to 15 years, 13,270 hectares or 24 per cent is more than 15 years, 12,600 hectares or 23 per cent is below 3 years old, 7,310 hectares or 13 per cent is between four to seven years old and 5,200 hectares or 10 per cent is in the range of three to four years old,” he said.
Whilst Rimbunan Sawit does not plan to acquire more plantation landbank in the near future, the plantation company is focusing on planting some 2,500 hectares of plantation landbank this year mostly at its estates in Kuching and Miri region.
The company revealed that its plantation landbank is located at Sibu, Kuching and Miri noting that its wholly-owned subsidiary Nescaya Palma Sdn Bhd which plantation estate is located close to Sibu has the highest yield at 18 MT per hectare in 2013.
On the CPO price outlook, the company opined that it will move in the range of RM2,300 to RM2,500 per MT this year.
As for Rimbunan Sawit’s financial performance for FY14, the company is expecting a marginal increase in overall results with average CPO price realised at about RM2,400 per MT.

ANALYSTS VIEW ON SARAWAK PLANTERS
The research arm of Affin Investment Bank Bhd (Affin Research) in its latest report dated July 8 said Ta Ann’s palm oil division remains a key earnings contributor to the group, at 70 per cent of the group’s total profit before tax for financial year estimate of 2014 to 2016.
The research firm observed that the higher earnings should be supported by increasing maturity of its plantation estates and rising FFB and CPO production as well as yield.
Affin Research said, “We forecast Ta Ann’s matured plantation area of 27,958 hectares as at December 2013 to increase to 30,911 hectares in FY14 and 35,345 hectares in FY15.
“Based on this, we expect FFB and CPO production to continue increasing given Ta Ann’s young weighted average age profile of trees, approximately six to seven years, along with anticipation of higher FFB yield from 18.9 per cent in 2013 to 20 per cent in FY14.
“As at end of May, Ta Ann’s FFB and CPO production increased by 14.9 per cent y-o-y and 55.5 per cent y-o-y to 197,307 MT and 43,592 MT respectively.
RHB Research in a report on May 12 said SOP’s plantation yield is expected to start climbing in 2015 or latest by 2016 after declining in the past five years due to new plantation reaching maturity.
The research firm observed the slowdown for SOP’s newly mature plantation area this year onwards will result in its FFB yield eventually rising.
As for SOP’s acquisition of two companies earlier, RHB Research estimated that the deal is expected to be completed in September and is projected to contribute about 100,000 tonnes of FFB per year from next year onwards.
The research firm noted that SOP had earlier proposed to acquire 60 per cent stake in two companies namely DD Pelita Sebungan Plantation Sdn Bhd and Mutiara Pelita Genaan Plantation Sdn Bhd for RM134.9 million to be funded through a combination of cash and shares.
RHB Research cited the two companies have collectively planted area of 9,660 hectares and the acquisition has translated into a bargain of RM23,275 per hectare, considering the soil is mineral soil.
The research firm further observed that the acquired asset also has some 5,000 hectares of new planting to be done.
Over the long term, RHB Research said SOP is targeting to reach 100,000 hectares of planted area.
The research arm of Maybank Investment Bank Bhd (Maybank Research) said SOP’s FFB production are highly yielded towards the second half of the year.
Maybank Research observed that over the past four years, approximately 58 per cent of SOP yearly FFB output was recorded in the second half of the year.
It noted that typically, the first quarter is the plantation company’s lowest quarter in terms of FFB output and the production is forecasted to peak in the third quarter of a year.
Over the medium term, Maybank Research believed that the prospect of SOP remains bright supported by the company’s three-year compound annual growth rate (CAGR) of FFB output estimated at 12 per cent for 2013 to 2016 and the unlocking of the plantation company’s oil palm estates value near Miri through property development over the next three to five years.

Read more: http://www.theborneopost.com/2014/07/13/el-nino-a-wild-card-for-planters/#ixzz37Pnazi9h

2014年2月23日星期日

El Nino Wikipedia

聖嬰-南方振盪現象

维基百科,自由的百科全书
(重定向自厄爾尼諾)
1997年由TOPEX/Poseidon卫星观测到的厄尔尼诺事件。南美和北美赤道区域海岸外的白色区域暗示暖水汇集。[1]
1876-2011间的南方涛动指数的时间序列。
来自NOAA的图片显示了1950-2011期间的全球年平均温度异常,ENSO时间被用红色和蓝色标出。
聖嬰-南方振盪現象(El Niño-Southern Oscillation,簡稱ENSO),或厄尔尼诺/拉尼娜-南方振盪是发生在横跨赤道附近太平洋的一种準周期气候类型,大约每5年发生一次。南方振盪 是指东太平洋赤道区域海面温度(厄尔尼诺 事件时变暖,拉尼娜 事件时变冷)和西太平洋赤道区域的海面上气压的变动。这两种变动是相互联系的:东太平洋的暖洋阶段,即厄尔尼诺,伴随着西太平洋的高海面气压;东太平洋的变冷阶段,即拉尼娜,伴随着西太平洋的低海面气压。[2][3]导致这种变动的机制仍在研究中。
这种气候类型变动的极端时期,即厄尔尼诺和拉尼娜事件,会在世界很多区域引起极端的天气(比如洪水和干旱)。依靠农业和渔业的发展中国家,特别是太平洋沿岸的国家,所受影响最大。厄尔尼诺-南方振盪比较流行的称呼常常省略为“厄尔尼诺”。厄尔尼诺是西班牙语,意指“小男孩”,指的是圣子耶稣,因为南美太平洋的变暖时期通常都在圣诞节附近。[4]

名稱


太平洋平時狀態:赤道風將溫水向西吹、冷水沿南美洲海岸上湧

聖嬰現象:溫水向南美洲吹送,冷水不再上湧而使海洋變暖;注意此時太平洋東西氣壓亦隨之變動,即所謂南方振盪
早期學者以為兩現象各自獨立,但近年來的研究漸漸闡明其關係、是一體的兩面,故以聖嬰-南方振盪現象稱之,學界一般通用縮寫ENSO。

聖嬰現象

東太平洋漁民很早便發現每隔數年,該地的海水就會異常升溫,因此沿海一帶的漁民以西班牙語「El Niño」(音譯:厄尔尼诺,意為「男嬰」或「聖嬰」,因為此种气候现象通常於聖誕節前后开始发生)稱呼此異常氣候。而相反的現象稱為「La Niña」意為「女嬰」或「聖女(嬰)」,或譯作「反聖嬰」。
海水變暖的範圍主要為太平洋東部與中部的熱带海洋的海水溫度異常地持續變暖,使整个世界气候模式发生变化,造成一些地区干旱而另一些地区又降雨量过多。其出現頻率並不規則,但平均約每4年發生一次。基本上,如果現象持續期少於五個月,會稱為聖嬰情況(condition);如果持續期是五個月或以上,便會稱為聖嬰事件(episode)。
根據海水變暖的中心區域不同,又將聖嬰分為中太平洋聖嬰Central Pacific (CP) El Niño與東太平洋聖嬰Eastern Pacific (EP) El Niño。

南方振盪

南方振盪為聖嬰現象在大氣的對應關係,不過早期學者並不了解這點。所謂的「振盪」(oscillation)是指赤道附近太平洋東西處之氣壓變化,最早由英國氣象學家沃克(Gilbert Walker)於20世紀初期發現並提出。
南方振盪的強度由所謂的「南方振盪指數」(Southern Oscillation Index,SOI)評估之,也就是選定塔希提與澳洲達爾文兩地作為東、西太平洋的代表地,指數指出了兩地之氣壓差距。[5]當聖嬰現象時其值為負,意指大溪地(東)氣壓低於達爾文(西)。

成因

ENSO形成的原因,科学界有多种观点,比较普遍的看法是:在正常状况下,北半球赤道附近吹东北信风,南半球赤道附近吹东南信风。信风带动海水自东向西流动,分别形成北赤道洋流和南赤道暖流。从赤道东太平洋流出的海水,靠海洋底部的湧升流补充,由於底層海水溫度較低,因此使表面水温低于四周,形成东西部海温差。但是,一旦東風减弱,甚至变为西风时,赤道东太平洋地区的冷水上翻减少或停止,海水温度就升高,形成大范围的海水温度异常增暖。而突然增强的这股暖流沿着厄瓜多爾海岸南侵,使海水温度剧升,冷水鱼群因而大量死亡,海鸟因找不到食物而纷纷离去,渔场顿时失去生机,使沿岸国家遭到巨大损失。
ENSO形成的前兆包括:
  • 印度洋、印尼與澳洲氣壓上升;
  • 大溪地和太平洋中央、東面的海面氣壓下降;
  • 南太平洋的信風減弱或往東面吹;
  • 秘魯附近的暖空氣上升,令當地沙漠下雨;
  • 暖空氣由太平洋西岸擴散至印度洋與太平洋東面。同時它令東面較乾燥和有乾旱的地方降雨。

影响

  • ENSO規模顯著的年份:1790-93、1828、1876-78、1891、1925-26、1982-83、1997-98。
  • 近年、但規模較小的年份:1986-1987、1990-1994、2002-2004、2006-2007、2009-2010。
  • 1982年4月至1983年7月的ENSO现象,是几个世纪来最严重的一次之一,太平洋東部至中部水面溫度比正常高出約4至5℃,造成全世界1300~1500人丧生,经济损失近百亿美元。
  • 1986年至1987年的ENSO现象,使赤道中、东太平洋海水表面水温比常年平均温度偏高2℃左右;同时,热带地区的大气环流也相应地出现异常,热带及其他地区的天气出现异常变化;南美洲的秘鲁北部、中部地区暴雨成灾;哥伦比亚境内的亚马孙河河水猛涨,造成河堤多次决口;巴西东北部少雨干旱,西部地区炎热;澳大利亚东部及沿海地区雨水明显减少;中国华南地区、南亚至非洲北部大范围地区均少雨干旱。
  • 1990年初又发生ENSO前兆现象。这年1月,太平洋中部海域水面温度高于往年,除赤道海域水面温度比往年高出0.5℃外,国际換日線以西的海域水面温度也比往年高出将近1℃;接近海面的28℃的暖水层比往年浅10米左右;南美洲太平洋沿岸水域的水位比平时上涨15~30厘米。
  • 1997年至1998年的ENSO现象,亦是几个世纪来最严重的一次之一,太平洋東部至中部水面溫度比正常高出約3至4℃,美洲地區有持續暴雨,東南亞地區则持续干旱并發生大規模的森林大火。這次聖嬰現象緊接1990-1994年發生,頻密程度罕見。
  • 同时,ENSO带动的温暖海水,影响鱼类的成群移动,破坏珊瑚礁的生长。
  • 特別的是,在聖嬰現象發生當年,容易在西北太平洋和東北太平洋形成威力強大的颱風和颶風。例如:1997年太平洋颱風季當年就曾出現十個威力達到等級最高的五級颱風,在1997年太平洋颶風季也出現兩個等級最高的五級颶風分別是:颶風琳達和颶風蓋勒摩。2002年太平洋颶風季三個等級最高颶風和2009年太平洋颱風季四個等級最高的五級颱風。以及2009年太平洋颶風季僅次於1997年琳達颶風的:颶風瑞克。

ENSO和全球变暖

在过去的几十年中,厄尔尼诺事件的数目有所增加,而拉尼娜事件的数目却在减少。[6]我们可能还需要观察ENSO更长的时间以发现稳定的变化[7],我们现在还不清楚这到底是随机的波动,或是ENSO的正常变化规律,还是由走向全球变暖的全球气候变化所导致。
对历史数据的研究表明,最近的厄尔尼诺的变化很可能和全球变暖有关。比如,一个最近的研究显示,即使减去十年际变化率的正影响后再看ENSO的趋势[8],观测数据中的ENSO变率的幅度仍然显示在增加,在过去50年里最大增加了60%。[9]
现在还不是很确定ENSO在将来会如何变化[10],不同的模式得出了不同的预测结果。[11]可能现在观测到的更强更频繁的厄尔尼诺事件只是发生在全球变暖的早期阶段,然后(比如在海洋低层也变暖后),厄尔尼诺将可能变得比现在要弱些。[12]也有可能,影响ENSO的各种因素的最后效果被最终相互抵消。[13]要想更好的预测ENSO的将来变化还需要更多的研究。ENSO被认为是地球气候的一个潜在的临界元素(tipping element)。[14]



聖嬰現象(ENSO)

「聖嬰」一詞源自西班牙文,(英文翻譯為Christ Child),意為上帝之子,是100多年前南美洲 秘魯和厄瓜多的漁民用來稱呼發生於聖誕節前後,祕魯附近海域海溫異常偏暖的現象。科學研究顯示 不僅和祕魯附近海溫的變化有關,也和熱帶東太平洋和西太平洋之間的海面氣壓的分布有關,就以 El Nino Southern Oscillation(簡稱ENSO)來表示熱帶太平洋大氣和海洋之間的變化,也就 是一般所謂的聖嬰現象。
ENSO是赤道太平洋附近大氣和海洋最顯著的現象,通常最容易發生在冬季。當赤道太平洋附近( 北緯5°至南緯5°、西經170-120°)3個月移動平均的海溫指標連續5個月比平均值高0.5℃時,就 認定為ENSO暖事件(就是一般通稱的聖嬰事件);當3個月移動平均的海溫指標連續5個月比平均值 低0.5℃時,就認定為ENSO冷事件(就是一般通稱的反聖嬰事件),聖嬰和反聖嬰事件發生時大氣和 海洋的狀況說明於圖1。
ENSO現象雖然主要發生在赤道太平洋附近,但卻對全球各地的氣候都會造成影響,因此,深受各國 氣象單位的重視,其中對各地較顯著之影響列於圖2。臺灣雖不在ENSO事件的主要影響區域,一般 而言,當強的聖嬰事件(即指標超過1.5℃)發生時的冬天,臺灣易出現暖冬、隔年易出現春雨偏多 的情形,而颱風生成的位置則有距離臺灣較遠的現象。當強的反聖嬰事件(即指標超過-1.5℃)發生 時的冬天,臺灣易出現冷冬、隔年易出現冷夏,颱風生成的位置會距臺灣較近。不過,研究顯示每 個ENSO事件的差異性相當大。
氣象局分析臺灣的春雨,得知除了受聖嬰影響外,也和印度洋的海溫變化有關。另外,近幾年聖嬰 現象的位置也較過去典型聖嬰現象發生時偏西,是所謂的非典型聖嬰。因此在預測臺灣的氣候時, 除了參考ENSO的預報資訊,還會參考氣候電腦模擬和統計分析的結果。
詳細聖嬰事件的分析和預報可參考本局於每月月中發布的氣候監測報告 (http://www.cwb.gov.tw/V6/statistics/watch/watch.php),臺灣的氣候預報可參考 本局於每月月底發布的季長期天氣展望(http://www.cwb.gov.tw/V6/forecast/long/long_season.htm)。

聖嬰事件示意圖
反聖嬰事件示意圖
聖嬰事件示意圖
反聖嬰事件示意圖
圖1:左圖當聖嬰事件發生時,暖海水(圖中紅與橙色部分)向東偏移、赤道地區的信風(東風)減弱出 現西風的距平,隨著暖海溫的東移,熱帶地區主要降雨的位置也會跟著往東移。右圖當反聖嬰事件 發生時,偏暖海水(圖中紅與橙色部分)位於西太平洋附近、赤道地區的東風偏強,熱帶地區主要降 雨的位置也會跟著往西移。圖片來源www.pmel.noaa.gov。
Warm episode relationships Jun-Aug
Cold episode relationships Jun-Aug
Warm episode relationships Dec-Feb
Cold episode relationships Dec-Feb
圖2:左上圖為聖嬰事件發生時夏季於印尼群島易出現乾旱、換日線附近出現多雨,中南美洲易出 現高溫少雨。左下圖為聖嬰事件發生時冬季的日本、臺灣、中南半島及加拿大西岸易出現高溫,美 國東南部易出現濕冷的天氣。右上圖為反聖嬰事件發生時夏季於臺灣及中南半島易出現偏冷的天氣、 印度及蘇門達臘群島易出現濕冷的天氣、澳洲東南部出現偏暖的天氣。右下圖為反聖嬰事件發生時 冬季於日本韓國及加拿大西岸易出現偏冷的天氣、印尼及菲律賓易出現多雨的天氣。圖片來源 www.pmel.noaa.gov。


El Niño

From Wikipedia, the free encyclopedia
The 1997 El Niño observed by TOPEX/Poseidon. The white areas off the tropical coasts of South and North America indicate the pool of warm water[1]
Southern Oscillation Index timeseries 1876-2012.
NOAA graph of Global Annual Temperature Anomalies 1950–2012, showing ENSO
El Niño (/ɛlˈniːnjoʊ/, /-ˈnɪn-/, Spanish pronunciation: [el ˈniɲo]) is a band of anomalously warm ocean water temperatures that periodically develops off the western coast of South America and can cause climatic changes across the Pacific Ocean. There is a phase of 'El Niño–Southern Oscillation' (ENSO), which refers to variations in the temperature of the surface of the tropical eastern Pacific Ocean (El Niño and La Niña) and in air surface pressure in the tropical western Pacific. The two variations are coupled: the warm oceanic phase, El Niño, accompanies high air surface pressure in the western Pacific, while the cold phase, La Niña, accompanies low air surface pressure in the western Pacific.[2][3] Mechanisms that cause the oscillation remain under study.
The extremes of this climate pattern's oscillations cause extreme weather (such as floods and droughts) in many regions of the world. Developing countries dependent upon agriculture and fishing, particularly those bordering the Pacific Ocean, are the most affected. El niño is Spanish for "the boy", and the capitalized term El Niño refers to the Christ child, Jesus, because periodic warming in the Pacific near South America is usually noticed around Christmas.[4]

Definition

El Niño is defined by prolonged warming in the Pacific Ocean sea surface temperatures when compared with the average value. The accepted definition is a warming of at least 0.5°C (0.9°F) averaged over the east-central tropical Pacific Ocean. Typically, this anomaly happens at irregular intervals of two to seven years, and lasts nine months to two years.[5] The average period length is five years. When this warming occurs for only seven to nine months, it is classified as El Niño "conditions"; when it occurs for more than that period, it is classified as El Niño "episodes".[6] Similarly, La Niña conditions and episodes are defined for cooling.
The first signs of an El Niño are:
  1. Rise in surface pressure over the Indian Ocean, Indonesia, and Australia
  2. Fall in air pressure over Tahiti and the rest of the central and eastern Pacific Ocean
  3. Trade winds in the south Pacific weaken or head east
  4. Warm air rises near Peru, causing rain in the northern Peruvian deserts
  5. Warm water spreads from the west Pacific and the Indian Ocean to the east Pacific. It takes the rain with it, causing extensive drought in the western Pacific and rainfall in the normally dry eastern Pacific.
El Niño's warm rush of nutrient-poor water heated by its eastward passage in the Equatorial Current, replaces the cold, nutrient-rich surface water of the Humboldt Current. When El Niño conditions last for many months, extensive ocean warming and the reduction in easterly trade winds limits upwelling of cold nutrient-rich deep water, and its economic impact to local fishing for an international market can be serious.[7]

Southern Oscillation


Normal Pacific pattern: Equatorial winds gather warm water pool toward the west. Cold water upwells along South American coast. (NOAA / PMEL / TAO)
The Southern Oscillation is the atmospheric component of El Niño. This component is an oscillation in surface air pressure between the tropical eastern and the western Pacific Ocean waters. The strength of the Southern Oscillation is measured by the Southern Oscillation Index (SOI). The SOI is computed from fluctuations in the surface air pressure difference between Tahiti and Darwin, Australia.[8] El Niño episodes are associated with negative values of the SOI, meaning there is below normal pressure over Tahiti and above normal pressure of Darwin.
Low atmospheric pressure tends to occur over warm water and high pressure occurs over cold water, in part because of deep convection over the warm water. El Niño episodes are defined as sustained warming of the central and eastern tropical Pacific Ocean. This results in a decrease in the strength of the Pacific trade winds, and a reduction in rainfall over eastern and northern Australia.

Walker circulation


El Niño conditions: Warm water pool approaches the South American coast. The absence of cold upwelling increases warming.

La Niña conditions: Warm water is farther west than usual.
During non-El Niño conditions, the Walker circulation is seen at the surface as easterly trade winds that move water and air warmed by the sun toward the west. This also creates ocean upwelling off the coasts of Peru and Ecuador and brings nutrient-rich cold water to the surface, increasing fishing stocks. The western side of the equatorial Pacific is characterized by warm, wet, low-pressure weather as the collected moisture is dumped in the form of typhoons and thunderstorms. The ocean is some 60 cm (24 in) higher in the western Pacific as the result of this motion.[9][10][11][12]

Effects of ENSO warm phase (El Niño)

South America

Because El Niño's warm pool feeds thunderstorms above, it creates increased rainfall across the east-central and eastern Pacific Ocean, including several portions of the South American west coast. The effects of El Niño in South America are direct and stronger than in North America. An El Niño is associated with warm and very wet weather months in April–October along the coasts of northern Peru and Ecuador, causing major flooding whenever the event is strong or extreme.[13] The effects during the months of February, March, and April may become critical. Along the west coast of South America, El Niño reduces the upwelling of cold, nutrient-rich water that sustains large fish populations, which in turn sustain abundant sea birds, whose droppings support the fertilizer industry. The reduction in upwelling leads to fish kills off the shore of Peru.[7]
The local fishing industry along the affected coastline can suffer during long-lasting El Niño events. The world's largest fishery collapsed due to overfishing during the 1972 El Niño Peruvian anchoveta reduction. During the 1982–83 event, jack mackerel and anchoveta populations were reduced, scallops increased in warmer water, but hake followed cooler water down the continental slope, while shrimp and sardines moved southward, so some catches decreased while others increased.[14] Horse mackerel have increased in the region during warm events. Shifting locations and types of fish due to changing conditions provide challenges for fishing industries. Peruvian sardines have moved during El Niño events to Chilean areas. Other conditions provide further complications, such as the government of Chile in 1991 creating restrictions on the fishing areas for self-employed fishermen and industrial fleets.
The ENSO variability may contribute to the great success of small, fast-growing species along the Peruvian coast, as periods of low population removes predators in the area. Similar effects benefit migratory birds that travel each spring from predator-rich tropical areas to distant winter-stressed nesting areas.
Southern Brazil and northern Argentina also experience wetter than normal conditions, but mainly during the spring and early summer. Central Chile receives a mild winter with large rainfall, and the Peruvian-Bolivian Altiplano is sometimes exposed to unusual winter snowfall events. Drier and hotter weather occurs in parts of the Amazon River Basin, Colombia, and Central America.

North America


Regional impacts of warm ENSO episodes (El Niño)
Winters, during the El Niño effect, are warmer and drier than average in the Northwest, northern Midwest, and northern Mideast United States, so those regions experience reduced snowfalls. Meanwhile, significantly wetter winters are present in northwest Mexico and the southwest United States, including central and southern California, while both cooler and wetter than average winters in northeast Mexico and the southeast United States (including the Tidewater region of Virginia) occur during the El Niño phase of the oscillation.[15][16]
Some believed the ice storm in January 1998, which devastated parts of southern Ontario and southern Quebec, was caused or accentuated by El Niño's warming effects.[17] El Niño warmed Vancouver for the 2010 Winter Olympics, such that the area experienced a subtropical-like winter during the games.[18]
El Niño is credited with suppressing hurricanes, and made the 2009 hurricane season the least active in 12 years.[19]

Tropical cyclones

Most tropical cyclones form on the side of the subtropical ridge closer to the equator, then move poleward past the ridge axis before recurving into the main belt of the Westerlies.[20] When the subtropical ridge position shifts due to El Niño, so will the preferred tropical cyclone tracks. Areas west of Japan and Korea tend to experience much fewer September–November tropical cyclone impacts during El Niño and neutral years. During El Niño years, the break in the subtropical ridge tends to lie near 130°E, which would favor the Japanese archipelago.[21] During El Niño years, Guam's chance of a tropical cyclone impact is one-third of the long-term average.[22] The tropical Atlantic ocean experiences depressed activity due to increased vertical wind shear across the region during El Niño years.[23] On the flip side, however, the tropical Pacific Ocean east of the dateline has above-normal activity during El Niño years due to water temperatures well above average and decreased windshear.[24] Most of the recorded East Pacific category 5 hurricanes occur during El Niño years in clusters.

Elsewhere

In Africa, East Africa — including Kenya, Tanzania, and the White Nile basin — experiences, in the long rains from March to May, wetter-than-normal conditions. Conditions are also drier than normal from December to February in south-central Africa, mainly in Zambia, Zimbabwe, Mozambique, and Botswana. Direct effects of El Niño resulting in drier conditions occur in parts of Southeast Asia and Northern Australia, increasing bush fires, worsening haze, and decreasing air quality dramatically. Drier-than-normal conditions are also in general observed in Queensland, inland Victoria, inland New South Wales, and eastern Tasmania from June to August.
Many ENSO linkages exist in the high southern latitudes around Antarctica.[25] Specifically, El Niño conditions result in high pressure anomalies over the Amundsen and Bellingshausen Seas, causing reduced sea ice and increased poleward heat fluxes in these sectors, as well as the Ross Sea. The Weddell Sea, conversely, tends to become colder with more sea ice during El Niño. The exact opposite heating and atmospheric pressure anomalies occur during La Niña.[26] This pattern of variability is known as the Antarctic dipole mode, although the Antarctic response to ENSO forcing is not ubiquitous.[26]
El Niño's effects on Europe appear to be strongest in winter. Recent evidence indicates that El Niño causes a colder, dryer winter in Northern Europe and a milder, wetter winter in Southern Europe.[27] The El Niño winter of 2009/10 was extremely cold in Northern Europe but El Niño is not the only factor at play in European winter weather and the weak El Niño winter of 2006/2007 was unusually mild in Europe, and the Alps recorded very little snow coverage that season.[28]
In more recent times, Singapore experienced the driest February in 2010 since records begins in 1869, with only 6.3 mm of rain falling in the month and temperatures hitting as high as 35°C on 26 February. The years 1968 and 2005 had the next driest Februaries, when 8.4 mm of rain fell.[29]

Effects of ENSO's cool phase (La Niña)


Sea surface skin temperature anomalies in November 2007 showing La Niña conditions
La Niña is the name for the cold phase of ENSO, during which the cold pool in the eastern Pacific intensifies and the trade winds strengthen. The name La Niña originates from Spanish, meaning "the girl", analogous to El Niño meaning "the boy". It has also in the past been called anti-El Niño, and El Viejo (meaning "the old man").[30]

Africa

La Niña results in wetter-than-normal conditions in Southern Africa from December to February, and drier-than-normal conditions over equatorial East Africa over the same period.[31]

Asia

During La Niña years, the formation of tropical cyclones, along with the subtropical ridge position, shifts westward across the western Pacific ocean, which increases the landfall threat to China.[21] In March 2008, La Niña caused a drop in sea surface temperatures over Southeast Asia by 2°C. It also caused heavy rains over Malaysia, the Philippines, and Indonesia.[32]

South America

During a time of La Niña, drought plagues the coastal regions of Peru and Chile.[33] From December to February, northern Brazil is wetter than normal.[33]

North America


Regional impacts of La Niña.
La Niña causes mostly the opposite effects of El Niño, above-average precipitation across the northern Midwest, the northern Rockies, Northern California, and the Pacific Northwest's southern and eastern regions. Meanwhile, precipitation in the southwestern and southeastern states is below average.[34] This also allows way above average hurricanes in the Atlantic and less in the Pacific.
La Niñas occurred in 1904, 1908, 1910, 1916, 1924, 1928, 1938, 1950, 1955, 1964, 1970, 1973, 1975, 1988, 1995, 1998, 2010, and 2011.[35] In Canada, La Niña will, in general, cause a cooler, snowier winter, such as the near-record-breaking amounts of snow recorded in the La Niña winter of 2007/2008 in Eastern Canada.[36] [37]

Transitional phases

Transitional phases at the onset or departure of El Niño or La Niña can also be important factors on global weather by affecting teleconnections. Significant episodes, known as Trans-Niño, are measured by the Trans-Niño index (TNI).[38] Examples of affected short-time climate in North America include precipitation in the Northwest US[39] and intense tornado activity in the contiguous US.[40]
During strong El Niño episodes, a secondary peak in sea surface temperature across the far eastern equatorial Pacific Ocean sometimes follows the initial peak.[41]

Recent occurrences

These maps compare temperatures in a given month to the long-term average temperature of that month from 1985 through 1997. Blue shows temperatures that were cooler than average, white shows near-average temperatures, and red shows where temperatures were warmer than average. The maps are made from data collected by the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) compared to historical data collected by a series of National Oceanic and Atmospheric Administration (NOAA) satellites.Some sea surface temperature anomalies are simply transient events, not part of a specific pattern or trend. Other anomalies are more meaningful. At irregular intervals (roughly every 3-6 years), the sea surface temperatures in the Pacific Ocean along the equator become warmer or cooler than normal. These anomalies are the hallmark of El Niño and La Niña climate cycles, which can influence weather patterns across the globe. This time series shows the building and subsiding of a La Niña event from early 2007 through mid-2008.
A strong La Niña episode occurred during 1988–1989. La Niña also formed in 1995 and from 1998–2000, and a minor one from 2000–2001. In recent times, an occurrence of El Niño started in September 2006[42] and lasted until early 2007.[43] From June 2007 on, data indicated a moderate La Niña event, which strengthened in early 2008 and weakened before the start of 2009; the 2007–2008 La Niña event was the strongest since the 1988–1989 event. The strength of the La Niña made the 2008 Atlantic hurricane season one of the most active since 1944; 16 named storms had winds of at least 39 mph (63 km/h), eight of which became 74 mph (119 km/h) or greater hurricanes.[19]
According to NOAA, El Niño conditions were in place in the equatorial Pacific Ocean starting June 2009, peaking in January–February. Positive SST anomalies (El Niño) lasted until May 2010. SST anomalies then transitioned into the negative (La Niña) and have now transitioned back to ENSO-neutral during April 2012. In early July, NOAA stated that El Niño conditions have a 50+% chance of developing during the Northern Hemisphere summer. As the 2012 Northern Hemisphere summer started to draw to a close, NOAA stated that El Niño conditions are likely to develop in August or September. The September 30, 2013 NOAA report indicates high probability of no El Niño or La Niña (ENSO-neutral) through Spring 2014.[37]

Remote influence on tropical Atlantic Ocean

A study of climate records has shown that El Niño events in the equatorial Pacific are generally associated with a warm tropical North Atlantic in the following spring and summer.[44] About half of El Niño events persist sufficiently into the spring months for the Western Hemisphere Warm Pool to become unusually large in summer.[45] Occasionally, El Niño's effect on the Atlantic Walker circulation over South America strengthens the easterly trade winds in the western equatorial Atlantic region. As a result, an unusual cooling may occur in the eastern equatorial Atlantic in spring and summer following El Niño peaks in winter.[46] Cases of El Niño-type events in both oceans simultaneously have been linked to severe famines related to the extended failure of monsoon rains.[47]

ENSO and global warming

During the last several decades, the number of El Niño events increased, and the number of La Niña events decreased,[48] although observation of ENSO for much longer is needed to detect robust changes.[49] The question is whether this is a random fluctuation or a normal instance of variation for that phenomenon or the result of global climate changes toward global warming.
The studies of historical data show the recent El Niño variation is most likely linked to global warming. For example, one of the most recent results, even after subtracting the positive influence of decadal variation, is shown to be possibly present in the ENSO trend,[50] the amplitude of the ENSO variability in the observed data still increases, by as much as 60% in the last 50 years.[51]
The exact changes happening to ENSO in the future is uncertain:[52] Different models make different predictions.[53][54] It may be that the observed phenomenon of more frequent and stronger El Niño events occurs only in the initial phase of the global warming, and then (e.g., after the lower layers of the ocean get warmer, as well), El Niño will become weaker than it was.[55] It may also be that the stabilizing and destabilizing forces influencing the phenomenon will eventually compensate for each other.[56] More research is needed to provide a better answer to that question. The ENSO is considered to be a potential tipping element in Earth's climate.[57]

The "Modoki" or Central-Pacific El Niño debate


Map showing Niño3.4 and other index regions

Map of Atlantic major hurricanes during post-"Modoki" seasons, including 1987, 1992, 1995, 2003 and 2005.
The traditional Niño, also called Eastern Pacific (EP) El Niño,[58] involves temperature anomalies in the Eastern Pacific. However, in the last two decades, nontraditional El Niños were observed, in which the usual place of the temperature anomaly (Niño 1 and 2) is not affected, but an anomaly arises in the central Pacific (Niño 3.4).[59] The phenomenon is called Central Pacific (CP) El Niño,[58] "dateline" El Niño (because the anomaly arises near the dateline), or El Niño "Modoki" (Modoki is Japanese for "similar, but different").[60][61][62][63] There are flavors of ENSO additional to EP and CP types and some scientists argue that ENSO exists as a continuum often with hybrid types.[64]
The effects of the CP El Niño are different from those of the traditional EP El Niño—e.g., the new El Niño leads to more hurricanes more frequently making landfall in the Atlantic.[65]
The recent discovery of El Niño Modoki has some scientists believing it to be linked to global warming.[66] However, comprehensive satellite data go back only to 1979. More research must be done to find the correlation and study past El Niño episodes. More generally, there is no scientific consensus on how/if climate change may affect ENSO.[52]
There is also a scientific debate on the very existence of this "new" ENSO. Indeed, a number of studies dispute the reality of this statistical distinction or its increasing occurrence, or both, either arguing the reliable record is too short to detect such a distinction,[67][68] finding no distinction or trend using other statistical approaches,[69][70][71][72][73] or that other types should be distinguished, such as standard and extreme El Niños.[74][75] Following the asymmetric nature of the warm and cold phases of ENSO, a study could not identify such distinctions for La Niña, both in observations and in the climate models.[76]
The first recorded El Niño that originated in the central Pacific and moved toward the east was in 1986.[77]

Health and social impacts of El Niño

Extreme weather conditions related to the El Niño cycle correlate with changes in the incidence of epidemic diseases. For example, the El Niño cycle is associated with increased risks of some of the diseases transmitted by mosquitoes, such as malaria, dengue, and Rift Valley fever[citation needed]. Cycles of malaria in India, Venezuela, Brazil, and Colombia have now been linked to El Niño. Outbreaks of another mosquito-transmitted disease, Australian encephalitis (Murray Valley encephalitis—MVE), occur in temperate south-east Australia after heavy rainfall and flooding, which are associated with La Niña events. A severe outbreak of Rift Valley fever occurred after extreme rainfall in north-eastern Kenya and southern Somalia during the 1997–98 El Niño.[78]
ENSO conditions have also been related to Kawasaki disease incidence in Japan and the west coast of the United States,[79] via the linkage to tropospheric winds across the north Pacific Ocean.[80]
ENSO may be linked to civil conflicts. Scientists at The Earth Institute of Columbia University, having analyzed data from 1950 to 2004, suggest ENSO may have had a role in 21% of all civil conflicts since 1950, with the risk of annual civil conflict doubling from 3% to 6% in countries affected by ENSO during El Niño years relative to La Niña years.[81][82]

Cultural history and prehistoric information


Average equatorial Pacific temperatures
ENSO conditions have occurred at two- to seven-year intervals for at least the past 300 years, but most of them have been weak. Evidence is also strong for El Niño events during the early Holocene epoch 10,000 years ago.[83]
El Niño affected pre-Columbian Incas [84] and may have led to the demise of the Moche and other pre-Columbian Peruvian cultures.[85] A recent study suggests a strong El-Niño effect between 1789 and 1793 caused poor crop yields in Europe, which in turn helped touch off the French Revolution.[86] The extreme weather produced by El Niño in 1876–77 gave rise to the most deadly famines of the 19th century.[87] The 1876 famine alone in northern China killed up to 13 million people.[88]
An early recorded mention of the term "El Niño" to refer to climate occurred in 1892, when Captain Camilo Carrillo told the geographical society congress in Lima that Peruvian sailors named the warm north-flowing current "El Niño" because it was most noticeable around Christmas. The phenomenon had long been of interest because of its effects on the guano industry and other enterprises that depend on biological productivity of the sea.
Charles Todd, in 1893, suggested droughts in India and Australia tended to occur at the same time; Norman Lockyer noted the same in 1904. An El Niño connection with flooding was reported in 1895 by Pezet and Eguiguren. In 1924, Gilbert Walker (for whom the Walker circulation is named) coined the term "Southern Oscillation".
The major 1982–83 El Niño led to an upsurge of interest from the scientific community. The period 1990–1994 was unusual in that El Niños have rarely occurred in such rapid succession.[89] An especially intense El Niño event in 1998 caused an estimated 16% of the world's reef systems to die. The event temporarily warmed air temperature by 1.5°C, compared to the usual increase of 0.25°C associated with El Niño events.[90] Since then, mass coral bleaching has become common worldwide, with all regions having suffered "severe bleaching".[91]
Major ENSO events were recorded in the years 1790–93, 1828, 1876–78, 1891, 1925–26, 1972–73, 1982–83, 1997–98 and 2009–2010,[47] with 1997-1998 being one of the strongest ever.[92]