Summary of climate variations
Cooling over the past 50 million years Zachos et al. (2001) studied oxygen isotope ratios in ancient sedimentary deposits and thereby estimated deep-sea temperatures over the past 60 million years. Hansen et al. (2010) modified their results to take into account the fact that isotope data represent a combination of deep-sea temperature and ice sheet volume and, during periods when there were ice sheets, the data had to be corrected for this (see Figure 2.7). Deep-sea temperature dropped by about 12_C over the past 50 million years.
KeywordsGlobal Average Temperature Planktic Foraminifera Proglacial Lake Glacial Condition Global Average Temperature Change
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