冰雪地球的研究进展综述

在大约6~7亿年前的新元古代时期，地球是否曾经被冰雪完全覆盖而成为了一个“冰雪地球”？如果是，什么诱发了这种全球性的冰川期？又是什么导致了它的融化？新元古代时期的极端气候变化对其后的寒武纪生命大爆发有何影响？围绕这些问题，古地质、古生物和古气候学界在最近几年展开了广泛的研究和激烈争论。根据现有的研究结果，地球在新元古代时期确实经历了数次地球历史上最为严重的全球性冰川期，但地球是否被完全冰封还需要更充分的古地质和古生物方面的证据来证明；利用气候模式对各种可能的外部强迫的模拟试验表明“冰雪地球”是很难形成的，并且，如果地球进入完全被冰封的状态，它将是难以被融化的；关于新元古代时期剧烈的气候变化对寒武纪生命大爆发所起的作用存在2种观点，一种认为气候变化导致了原始生命的基因突变并诱发了寒武纪生命爆发，另一种认为这种影响主要是生态方面的。

ON STUDIES OF SNOWBALL EARTH

Had Earth ever been completely covered by snow and ice and become a giant "snowball Earth" during the Neoproterozoic about 600~700 million years before? If it had, what caused this global freezing? What led it to melt? What had the violate climate changes during the Neoproterozoic impacted on the Cambrian life explosion? In the past few years, these problems have drawn extensive studies and intensive controversies in the fields of paleo-geology, paleontology, and paleoclimatology. According to existing results, it is generally thought that during the Neoproterozoic Earth had experienced several most severe global glaciations in Earth's history. However, it needs further geological and paleo-biological evidence to prove whether Earth had been completely frozen or not; numerical simulations with various external forcings showed that the formation of a hard "snowball Earth" is almost impossible, and if Earth runs into complete freezing, it is hard to get back out; there are two controversial points of views that such violate climate changes during the Neoproterozoic might have important impacts on the Cambrian life explosion. One is that the climate changes can induce mutations that fuel biological innovation, and the other one is that the impacts are on ecosystems.