Department of Earth Sciences, Royal Holloway, Egham, UK.
Astrobiology. 2019 Nov;19(11):1388-1397. doi: 10.1089/ast.2018.1942. Epub 2019 Aug 7.
Lower heating of our planet by the young Sun was compensated by higher warming from factors such as greater greenhouse gas concentrations or reduced albedo. Earth's climate history has therefore been one of increasing solar forcing through time roughly cancelled by decreasing forcing due to geological and biological processes. The current generation of coupled carbon-cycle/climate models suggests that decreasing geological forcing-due to falling rates of outgassing, continent growth, and plate spreading-can account for much of Earth's climate history. If Earth-like planets orbiting in the habitable zone of red dwarfs experience a similar history of decreasing geological forcing, their climates will cool at a faster rate than is compensated for by the relatively slow evolution of their smaller stars. As a result, they will become globally glaciated within a few billion years. The results of this paper therefore suggest that coupled carbon-cycle/climate models account, parsimoniously, for both the faint young Sun paradox and the puzzle of why Earth orbits a relatively rare and short-lived star-type.
由于年轻太阳的加热作用较低，因此通过温室气体浓度增加或反照率降低等因素来补偿更高的升温。因此，地球的气候历史是一个随着时间的推移太阳辐射强迫逐渐增加的过程，而这种强迫大致被地质和生物过程引起的强迫减少所抵消。目前这一代的碳循环/气候耦合模型表明，由于脱气、大陆生长和板块扩张速率的下降，地质强迫的减少可以解释地球历史上的大部分气候变化。如果围绕红矮星宜居带运行的类地行星经历了类似的地质强迫减少的历史，那么它们的气候将比其较小恒星相对缓慢的演化更快地冷却。结果，它们将在几十亿年内成为全球性冰川。因此，本文的结果表明，碳循环/气候耦合模型可以简单地解释弱年轻太阳悖论和为什么地球围绕相对罕见且短暂的恒星类型运行的难题。
