14 Analysis of Prehistoric Air
古氣候學：介紹分析史前階段全球氣溫變化的方法

導讀

古氣候學是研究地質時期氣候形成的原因、過程、分布及其變化規律的學科。即根據物質成分、沉積巖結構特點和生物，按一定的理論和方法推斷各地質時代的氣候。重點是根據地質學上的證據，研究時間尺度在萬年以上的冰期與間冰期氣候。古氣候學的研究與地質學、古生物學、地球化學、同位素化學、大氣物理學和天文學等密切相關。本文介紹的是古氣候學中如何分析史前階段全球氣溫變化的方法。

 

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

句子翻譯

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．估計發生空氣被圈在氣泡中的那個時期的全球氣溫，取決于測量包圍氣泡的冰中的氫及其較重的同位素——重氫的相對豐度。

2．根據這個信息，結合分析圍在極地深層冰中空氣內的二氧化碳含量，就可以對全球氣溫作出估計。這個估計表明：在冰后期暖和階段，地球大氣中的二氧化碳增加大約40%。