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arXiv 1204.4449astro-ph.EPphysics.ao-phphysics.geo-ph
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微弱的年轻太阳问题

The faint young Sun problem

Georg Feulner

备注：
32 pages, 8 figures. Invited review paper accepted for publication in Reviews of Geophysics
发表信息：
Rev.Geophys. 50 (2012), RG2006
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摘要：

40多年来，科学家们一直试图找到古气候学中最基本问题之一的答案，即“微弱的年轻太阳问题”。对于早期的地球，恒星演化模型预测输入到气候系统的太阳能比今天低25%左右。如果控制地球气候的所有其他参数保持不变，这将导致我们星球历史上的头20亿年里世界完全冻结。然而，有充分的证据表明，在太古代（距今38亿至25亿年）存在液态地表水，甚至生命，因此一定有某种效应（或多种效应）弥补了年轻太阳的微弱。在过去的四十年里，人们提出并探索了各种可能的解决方案，大多数研究都集中在二氧化碳、甲烷或氨等大气温室气体浓度较高的问题上。然而，所有这些解决方案都存在相当大的困难，所以微弱的年轻太阳问题不能被视为已经解决。在这里，我回顾了关于这个问题的研究，包括最新的建议，为解决年轻的太阳微弱的问题和最近的地球化学限制地球的早期大气的组成。此外，我将概述未来研究的最有前途的方向。特别是，我认为，无论是改善地球化学的约束条件的太古代气候系统的状态和数值实验与国家的最先进的气候模型，最终需要评估是什么让海洋在太古代地球上完全冻结。

英文摘要：

For more than four decades, scientists have been trying to find an answer to one of the most fundamental questions in paleoclimatology, the `faint young Sun problem'. For the early Earth, models of stellar evolution predict a solar energy input to the climate system which is about 25% lower than today. This would result in a completely frozen world over the first two billion years in the history of our planet, if all other parameters controlling Earth's climate had been the same. Yet there is ample evidence for the presence of liquid surface water and even life in the Archean (3.8 to 2.5 billion years before present), so some effect (or effects) must have been compensating for the faint young Sun. A wide range of possible solutions have been suggested and explored during the last four decades, with most studies focusing on higher concentrations of atmospheric greenhouse gases like carbon dioxide, methane or ammonia. All of these solutions present considerable difficulties, however, so the faint young Sun problem cannot be regarded as solved. Here I review research on the subject, including the latest suggestions for solutions of the faint young Sun problem and recent geochemical constraints on the composition of Earth's early atmosphere. Furthermore, I will outline the most promising directions for future research. In particular I would argue that both improved geochemical constraints on the state of the Archean climate system and numerical experiments with state-of-the-art climate models are required to finally assess what kept the oceans on the Archean Earth from freezing over completely.

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