研究得出地球的冰冠從何而來

 原文網址：https://www.leeds.ac.uk/main-index/news/article/5733/research-reveals-how-earth-got-its-ice-caps

新研究表示在地球的歷史當中，讓地球得以形成冰冠的低溫條件是偶發事件，需要許多複雜的作用在同一時間進行才能達成。

里茲大學主持的科學團隊探討了為什麼在地球大部分的歷史當中，地球都是處於沒有冰冠的「溫室」狀態，而人類目前所處的環境條件則極為稀有。

目前地球表面有些地方被冰雪覆蓋，但他們發現這樣的狀態並非地球歷史中的常態，唯有透過相當幸運的巧合才能達成。

之前科學家提出許多概念來解釋地球歷史中已知的寒冷時期如何形成。這些概念包括了火山排出的二氧化碳減少、森林儲存的碳變多，或者是二氧化碳跟特定種類的岩石之間的化學反應增強。

此論文的研究人員首度把這些讓溫度降低的作用全部結合起來進行測試。他們所用的長時間尺度立體地球模型是由里茲大學率先開發出來，這種全新型態的「地球演化模型」有賴於近期電腦運算能力的進步才得以建立。

他們的結論認為任一作用都無法單獨造成這些寒冷的氣候時期，因此實際上需要同一時間發生數個作用，結合起來的效應才能導致這些冷期。研究結果今日(2025.2.14)發表於期刊《科學前緣》。

此發現有助於解開地球科學界的一道議題：哪些作用造成了這些地球歷史上的低溫時期？

主要作者Andrew Meredith博士任教於里茲大學地球與環境科學院的時候進行了這項研究，他說結果有助於解釋冰室狀態為什麼如此少見。

他解釋：「我們生活的地球為何是一顆有冰冠覆蓋，而不是沒有冰雪的星球。現在我們了解到這是因為某些因素恰好同時發生，像是全世界的火山活動相當不活躍；陸塊高度分散且有宏偉的山脈，使得全世界有豐沛的降水，也因此強化了可以從大氣移除二氧化碳的反應。」

「這項研究的重要涵義是地球氣候的自然調節機制偏好溫暖、二氧化碳含量高、沒有冰冠的世界，而非我們現在所處的二氧化碳含量低、部分被冰雪覆蓋的世界。」

「我們認為地球一般傾向於擁有溫暖的氣候，可以防止全球進入毀滅性的『雪球地球』冰河期。此現象在地球歷史上極為罕見，因此這股傾向確實有助於生命持續繁榮發展。」

里茲大學地球與環境學院研究地球系統演化的Benjamin Mills教授是此計畫的主持人。他補充研究結果對於全球暖化與不久之後的未來也有重要的涵義。

「此研究傳達出的重要訊息之一是，我們不應該期待地球一定會回到工業革命時代之前的低溫狀態，」他說。

「地球目前有冰雪覆蓋的狀態並非地球歷史上的常態，但是現在全世界的人類社會卻是依此而生。」

「我們應該竭盡全力來保護這種狀態，而且要謹慎看待如果我們停止排碳，地球就會回到寒冷氣候的看法，因為在此之前我們可能就已經造成過量的暖化了。地球在其漫長的歷史當中喜歡的是炎熱的氣候，但我們人類社會卻並非如此。」

 

Research reveals how Earth got its ice caps

The cool conditions which have allowed ice caps to form on Earth are rare events in the planet’s history and require many complex processes working at once, according to new research.

A team of scientists led by the University of Leeds investigated why Earth has existed in what is known as a 'greenhouse' state without ice caps for much of its history, and why the conditions we are living in now are so rare.

They found that Earth’s current ice-covered state is not typical for the planet’s history and was only achieved through a lucky coincidence.

Many ideas have previously been proposed to explain the known cold intervals in Earth’s history. These include decreased CO₂ emissions from volcanoes, or increased carbon storage by forests, or the reaction of CO₂ with certain types of rocks.

The researchers undertook the first ever combined test of all of these cooling processes in a new type of long-term 3D model of the Earth which was first developed at the University of Leeds. This type of ‘Earth Evolution Model’ has only recently been made possible through advances in computing.

They concluded that no single process could drive these cold climates, and that the cooling in fact required the combined effects of several processes at once. The results of their study are published today (14 February 2025) in the Journal Science Advances.

The findings will help to reconcile a debate in the Earth Science community about which processes were responsible for driving these cold periods.

Lead author, Dr Andrew Meredith, who carried out the research while working in the School of Earth and Environment at the University of Leeds, said the study helped to explain why icehouse states are so rare.

“We now know that the reason we live on an Earth with ice caps – rather than an ice-free planet – is due to a coincidental combination of very low rates of global volcanism, and highly dispersed continents with big mountains, which allow for lots of global rainfall and therefore amplify reactions that remove carbon from the atmosphere,” he explained.

“The important implication here is that the Earth’s natural climate regulation mechanism appears to favour a warm and high-CO₂ world with no ice caps, not the partially glaciated and low-CO₂ world we have today.  

“We think this general tendency towards a warm climate has helped prevent devastating 'snowball Earth' global glaciations, which have only occurred very rarely and have therefore helped life to continue to prosper.”

Benjamin Mills, Professor of Earth System Evolution in Leeds’ School of Earth and Environment, supervised the project. He added that the results of the research had important implications for global warming and the immediate future.

“There is an important message, which is that we should not expect the Earth to always return to a cold state as it was in the pre-industrial age,” he said.

“Earth’s current ice-covered state is not typical for the planet’s history, but our current global society relies on it. 

“We should do everything we can to preserve it, and we should be careful with assumptions that cold climates will return if we drive excessive warming before stopping emissions. Over its long history, the Earth likes it hot, but our human society does not.”

原始論文：Andrew S. Merdith, Thomas M. Gernon, Pierre Maffre, Yannick Donnadieu, Yves Goddéris, Jack Longman, R. Dietmar Müller, Benjamin J. W. Mills. Phanerozoic icehouse climates as the result of multiple solid-Earth cooling mechanisms. Science Advances, 2025; 11 (7) DOI: 10.1126/sciadv.adm9798

引用自：University of Leeds. "Research reveals how Earth got its ice caps."