科學家找出地球的冰期循環與公轉軌道變動的對應關係

 原文網址：https://news.ucsb.edu/2025/021777/scientists-match-earths-ice-age-cycles-orbital-shifts

地球大約從250萬年前開始進入一連串冰河期與間冰期交替出現的時代，並在11700年前左右離開最近一次的冰河期。一項新的分析結果提出下次冰河期的開始時間預計會在一萬年後。

科學家表示地球本來會在大約一萬年後進入另一個冰河時代，但是人類排放的溫室氣體可能已經劇烈改變氣候的走向。圖片來源：Matt Perko

這道預測是由加州大學聖塔巴巴拉分校的研究人員參與在內的國際團隊所提出。他們的根據是對地球繞日軌道的微小變化所得出的新理解，而這些變化會造成地球氣候出現為時數千年的重大改變。此篇發表於《科學》(Science)的研究追查了一段為時一百萬年地球氣候在自然情況下的循環變動，結果對於地球千變萬化的氣候系統提出了全新觀點，也是瞭解地球冰期循環的一大進展。

團隊探討了一段為時一百萬年的氣候變遷紀錄，其中記載了覆蓋北半球陸地的冰層大小以及深海的溫度變化。接著他們成功把這些變化對應至地球繞日軌道的形狀、地軸的擺動、地軸傾角這三者的微小週期性變動。

「我們發現在這一百萬年當中，地球氣候在冰河期與類似於現今的溫暖時期，稱為『間冰期』之間的來回變化模式是可以預測的，」共同作者，加州大學聖塔巴巴拉分校地球科學系的教授Lorraine Lisiecki表示。地球軌道的其中一種變化會造成冰河期結束，而另一種則和冰河期的回歸有關。

「我們在氣候紀錄中看到不同的軌道參數留下的指紋是如此明顯，使得我們相當訝異，」研究主要作者，英國卡迪夫大學的教授Stephen Barker接著表示。「難以相信此模式過往都沒有被觀察到。」

在一百多年前科學家就已經預測地球繞日軌道變化與冰期-間冰期狀態的來回動盪有所關聯，但是要到1970年代中期才有現實世界的數據佐證。從那時起，科學家便在努力找出對於冰期循環的開始與結束來說，哪一個軌道參數是最重要的，因為要定年如此久遠的氣候變遷並不容易。

團隊克服這道問題的方法是觀察氣候紀錄隨著時間的形狀變化。藉此他們辨認不同的參數要如何組合在一起，才能形成他們觀察到的氣候變遷。

作者發現過去90萬年每個冰河期都依循著可預測的模式出現。這種在沒有人類排放的溫室氣體的情況下所呈現出來的自然模式，指出我們現在應該位在一個穩定的間冰期中段，而下次冰河期則會在距今大約一萬年後到來。

「我們發現的模式具有相當高的再現性，使得我們可以精準預測過去一百萬年左右每一次的間冰期什麼時候會發生，而且持續多久，」Barker表示。「此發現的重要之處在於它證實了我們觀察到地球以數萬年為周期的自然氣候變遷，大多是可以預測的，而不是隨機發生或者混亂無序的。」這項發現對於冰期循環的統一理論來說具有重大貢獻。

「另一方面，因為我們正生活在稱為全新世的間冰期當中，因此我們也能經由此結果初步預測氣候可能會在什麼時候回到冰期的狀態，」共同作者，倫敦大學學院的教授Chronis Tzedakis表示。

「但是氣候很有可能不會在一萬年後轉換到冰期狀態，因為人類排放到大氣的二氧化碳已經讓氣候偏離它的自然軌跡，並在未來造成長遠的衝擊，」共同作者，德國亥姆霍茲極地與海洋研究中心的阿佛列•韋格納研究所的Gregor Knorr跟著表示。

團隊計畫以這項發現為基礎並將過去的氣候變遷標準化之後，建立出地球未來一萬到二萬年之間自然情況下氣候變遷的基準曲線。結合氣候模型的模擬結果，研究人員希望能以絕對的數值定量人為氣候變遷長遠下來的影響。

「既然我們知道在長時間尺度下氣候大致上是可以預測的，那我們就能利用過去的變化來告訴我們未來可能發生的事情，」Barker補充。「有了我們新的分析所具備的信心水準，才能辦到這件事。」

「我們現在對於溫室氣體排放的決策將決定未來氣候變遷的走向，因此這些能幫助下決策的訊息十分重要。」

 

Scientists match Earth’s ice age cycles with orbital shifts

Beginning around 2.5 million years ago, Earth entered an era marked by successive ice ages and interglacial periods, emerging from the last glaciation around 11,700 years ago. A new analysis suggests the onset of the next ice age could be expected in 10,000 years’ time.

An international team, including researchers from UC Santa Barbara, made their prediction based on a new interpretation of the small changes in Earth’s orbit of the sun, which lead to massive shifts in the planet’s climate over periods of thousands of years. The study tracks the natural cycles of the planet’s climate over a period of a million years. Their findings, published in Science, offer new insights into Earth’s dynamic climate system and represent a step-change in understanding the planet’s glacial cycles.

The team examined a million-year record of climate change, which documents changes in the size of land-based ice sheets across the Northern hemisphere together with the temperature of the deep ocean. They were able to match these changes with small cyclical variations in the shape of Earth's orbit of the sun, its wobble and the angle on which its axis is tilted.

“We found a predictable pattern over the past million years for the timing of when Earth's climate changes between glacial ‘ice ages’ and mild warm periods like today, called interglacials,” said co-author Lorraine Lisiecki, a professor in UCSB’s Earth Science Department. One type of change in Earth's orbit was responsible for the end of ice ages, while another was associated with their return.

“We were amazed to find such a clear imprint of the different orbital parameters on the climate record,” added lead author Stephen Barker, a professor at Cardiff University, in the UK. “It is quite hard to believe that the pattern has not been seen before.”

Predictions of a link between Earth’s orbit of the sun and fluctuations between glacial and interglacial conditions have been around for over a century but were not confirmed by real-word data until the mid-1970s. Since then, scientists have struggled to identify precisely which orbital parameter is most important for the beginning and ending of glacial cycles because of the difficulty of dating climatic changes so far back in time.

The team was able to overcome this problem by looking at the shape of the climate record through time. This allowed them to identify how the different parameters fit together to produce the climate changes observed.

The authors found that each glaciation of the past 900,000 years follows a predictable pattern. This natural pattern — in the absence of human greenhouse gas emissions — suggests that we should currently be in the middle of a stable interglacial and that the next ice age would begin many millennia in the future, approximately 10,000 years from now.

“The pattern we found is so reproducible that we were able to make an accurate prediction of when each interglacial period of the past million years or so would occur and how long each would last,” Barker said. “This is important because it confirms the natural climate change cycles we observe on Earth over tens of thousands of years are largely predictable and not random or chaotic.” These findings represent a major contribution towards a unified theory of glacial cycles.

“And because we are now living in an interglacial period – called the Holocene – we are also able to provide an initial prediction of when our climate might return to a glacial state,” said co- author Chronis Tzedakis, a professor at University College London.

“But such a transition to a glacial state in 10,000 years’ time is very unlikely to happen because human emissions of carbon dioxide into the atmosphere have already diverted the climate from its natural course, with longer-term impacts into the future,” added co-author Gregor Knorr from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research.

The team plans to build on their findings to create a baseline of the Earth’s natural climate for the next 10,000-20,000 years by calibrating past changes. Used in combination with climate model simulations, researchers hope to quantify the absolute effects of human-made climate change into the far future.

“Now we know that climate is largely predictable over these long timescales, we can actually use past changes to inform us about what could happen in the future,” Barker added. “This is something we couldn’t do before with the level of confidence that our new analysis provides.”

“This is vital for better informing decisions we make now about greenhouse gas emissions, which will determine future climate changes.”

原始論文：Stephen Barker, Lorraine E. Lisieck, Gregor Knorr, Sophie Nuber, Polychronis C. Tzedakis. Distinct roles for precession, obliquity, and eccentricity in Pleistocene 100-kyr glacial cycles. Science, 2025; DOI:10.1126/science.adp3491

引用自：The University of California, Santa Barbara. “Scientists match Earth’s ice age cycles with orbital shifts”