過往的聖嬰型態暗示了未來氣候變遷的趨勢

 原文網址：https://phys.org/news/2025-05-ancient-el-nio-patterns-hint.html

澳洲蒙納許大學主持的研究引起科學家重新思考聖嬰—南方震盪系統(ENSO)在過去是如何演變，以及目前持續變遷的氣候未來可能會讓它出現什麼樣的反應。

始新世早期是地球歷史上已知最溫暖的時期之一，全球溫度最高的時候比現在還多了15°C。這項研究對始新世早期的氣候系統進行了目前為止最為全面的探討，結果指出相較於今日，ENSO的兩個階段——即聖嬰與反聖嬰——在當時的強度都要來得更高，且持續時間也更長。

此研究發表於期刊《自然通訊》(Nature Communications,)，結果發現當時的高溫、較為寬廣的熱帶太平洋、不同於今日的全球地理分布狀況，三者結合起來重塑了負責調控海洋溫度的風與洋流系統。

ENSO是在熱帶太平洋來回變動的氣候型態，成因為海水溫度與大氣風場之間的交互作用。它有兩個不同的階段：聖嬰期與反聖嬰期。

聖嬰期通常會讓澳洲出現更為乾熱的天氣，而反聖嬰期一般則會帶來較多的雨量。

強烈的聖嬰期與反聖嬰期除了增加乾旱與洪水的風險之外，結合在溫度較高的始新世早期觀察到的其他變化，可能會改變氣候變異的程度，並且對全世界的海洋與大氣系統造成深遠的影響。

蒙納許大學地球、大氣與環境學院的研究員Abhik Santra博士是主要作者，他說這項發現不只讓我們更加瞭解過去的氣候，也揭示了未來的暖化可能會對熱帶太平洋的海氣耦合(ocean-atmosphere-coupled)氣候變異性產生什麼樣的影響。

「始新世早期熱帶太平洋的寬度大概是現在的1.5倍，」Santra博士說。

「這改變了海洋與大氣之間的作用方式，造成ENSO的強度增加，週期也比我們現今觀測到的還要長。」

「透過這些發現，我們對於聖嬰與反聖嬰背後的基本原理有了更深的理解。我們的結果也提供了重要的線索，讓我們推測在未來持續暖化的氣候當中，ENSO可能會有什麼樣的反應。」

為了瞭解全球暖化未來可能會讓ENSO出現什麼反應，研究人員必須先將兩種作用造成的效應給區分開來，分別為構造運動的變化以及溫室氣體引發的暖化。

他們針對此目的設計了氣候模型試驗，結果顯示構造運動和溫室氣體暖化對ENSO造成的影響恰好相反。

「關於ENSO未來的變化我們仍然沒有得出明確的共識，」Santra博士表示。「但是經由探討地球歷史上長期暖化的時期，我們的研究可以讓我們進一步地瞭解ENSO可能的演變方向。」

雖然許多氣候模型顯示ENSO的變異度在未來數十年會增加，但還是有很大的不確定性。

「一旦氣候暖化到達平衡點，溫度不再繼續升高的時候，ENSO有可能會稍微減弱。但這是相較於全球暖化期間ENSO達到的高峰，它還是有可能比現在來得更強，」Santra博士表示。「對於ENSO在暖化的世界中只會不斷變強的說法，我們提出了不同意見。」

「我們的研究顯示全球暖化與ENSO之間的反應，比過往認為的還要複雜。」

Santra博士和蒙納許大學的古氣候團隊目前計畫以此成果為基礎，更加深入地探討過往熱帶氣候的變異性。

透過揭露地球過往的氣候系統如何運作，他們的目標是蒐集重要的資訊，進而推測全球持續暖化的狀況下，地球的未來會是什麼樣子。

 

Ancient El Niño patterns hint at future climate trends

A Monash University-led study is prompting scientists to rethink how the El Niño-Southern Oscillation (ENSO) system evolved and how it might behave in the future as our climate continues to change.

The most comprehensive study to date of the climate system in the Early Eocene period, one of the warmest known periods in history, found ENSO's two phases, El Niño and La Niña, were both stronger and occurred over longer time intervals than they do today. During the Early Eocene, global temperatures were up to 15°C warmer than today.

The research, published in the journal Nature Communications, found this warmth, combined with a much wider tropical Pacific Ocean and different global geography, reshaped the winds and ocean currents that are responsible for regulating ocean temperatures.

ENSO is a recurring climate pattern in the tropical Pacific driven by interactions between ocean temperatures and atmospheric winds, with two distinct phases, El Niño and La Niña.

El Niño is generally responsible for warmer and drier weather in Australia, while La Niña typically brings higher rainfall.

In addition to drought or flooding risks that come with a strong El Niño or La Niña, changes in line with those observed during the warmer Early Eocene period could lead to an altered climate variability, with far-reaching impacts on global ocean and atmospheric systems.

Lead researcher Dr. Abhik Santra, Research Fellow at Monash School of Earth, Atmosphere and Environment, said the findings not only enhance our understanding of past climate but also shed light on how future warming could influence ocean-atmosphere-coupled climate variability in the tropical Pacific.

"In the Early Eocene, the tropical Pacific Ocean was about 1.5 times wider than it is today," Dr. Santra said.

"That changed the way the ocean and atmosphere interacted, resulting in a stronger ENSO with longer cycles than we observe in the present day.

"We have used these findings to get a better understanding of the basic processes behind El Niño and La Niña. Our results also offer important clues about how ENSO could behave in a future climate that remains persistently warm."

To understand how ENSO might respond to future global warming, researchers had to separate the effects of tectonic changes from those of greenhouse gas-driven warming.

They did this by running targeted climate model experiments, revealing that tectonics and greenhouse warming can affect ENSO in opposing ways.

"We still don't have a clear consensus on how ENSO will change in the future," Dr. Santra said. "But by examining periods of sustained warmth in Earth's history, our study brings us closer to understanding its possible evolution."

While many climate models suggest ENSO variability could increase in the coming decades, there's still significant uncertainty.

"Once the warmer climate reaches equilibrium and stops further rising in temperature, ENSO is likely to become slightly weaker, relative to its height during the increase of global warming, although still likely stronger than today," Dr. Santra said. "It challenges the idea that ENSO will simply strengthen in a warmer world.

"Our study shows the relationship between global warming and ENSO behavior is more complex than previously thought."

Dr. Santra and the Monash paleoclimate research team are now building on this work to further explore prehistoric tropical climate variability.

By uncovering more about Earth's ancient climate systems, they aim to gather vital clues about the planet's future under continued global warming.

原始論文：Santra Abhik, Dietmar Dommenget, Shayne McGregor, David K. Hutchinson, Sebastian Steinig, Jiang Zhu, Fabio A. Capitanio, Daniel J. Lunt, Igor Niezgodzki, Gregor Knorr, Wing-Le Chan, Ayako Abe-Ouchi. Stronger and prolonged El Niño-Southern Oscillation in the Early Eocene warmth. Nature Communications, 2025; DOI: 10.1038/s41467-025-59263-7

引用自：Phys.Org. “Ancient El Niño patterns hint at future climate trends.”