14 Analysis of Prehistoric Air
古气候学：介绍分析史前阶段全球气温变化的方法

导读

古气候学是研究地质时期气候形成的原因、过程、分布及其变化规律的学科。即根据物质成分、沉积岩结构特点和生物，按一定的理论和方法推断各地质时代的气候。重点是根据地质学上的证据，研究时间尺度在万年以上的冰期与间冰期气候。古气候学的研究与地质学、古生物学、地球化学、同位素化学、大气物理学和天文学等密切相关。本文介绍的是古气候学中如何分析史前阶段全球气温变化的方法。

Analysis of prehistoric air trapped in tiny bubbles beneath the polar ice sheets and of the composition of ice surrounding those bubbles suggests a correlation between carbon dioxide levels in the Earth's atmosphere and global temperature over the last 160,000 years. Estimates of global temperature at the time air in the bubbles was trapped rely on measuring the relative abundances of hydrogen and its heavier isotope, deuterium, in the ice surrounding the bubbles. When global temperatures are relatively low, water containing deuterium tends to condense and precipitate before reaching the poles; thus, ice deposited at the poles when the global temperature was cooler contained relatively less deuterium than ice deposited at warmer global temperatures. Estimates of global temperature based on this information, combined with analysis of the carbon dioxide content of air trapped in ice deep beneath the polar surface, suggest that during periods of postglacial warming carbon dioxide in the Earth's atmosphere increased by approximately 40 percent.

Sentence Translation

句子翻译

1. Estimates of global temperature at the time air in the bubbles was trapped rely on measuring the relative abundances of hydrogen and its heavier isotope, deuterium, in the ice surrounding the bubbles.

2. Estimates of global temperature based on this information, combined with analysis of the carbon dioxide content of air trapped in ice deep beneath the polar surface, suggest that during periods of postglacial warming carbon dioxide in the Earth's atmosphere increased by approximately 40 percent.

Key

1．估计发生空气被圈在气泡中的那个时期的全球气温，取决于测量包围气泡的冰中的氢及其较重的同位素——重氢的相对丰度。

2．根据这个信息，结合分析围在极地深层冰中空气内的二氧化碳含量，就可以对全球气温作出估计。这个估计表明：在冰后期暖和阶段，地球大气中的二氧化碳增加大约40%。