PPT13 - Long Term Climate Evolution

PPT13 - Long Term Climate Evolution - Long-Term Climate...

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Long-Term Climate Evolution and Regulation From geological evidence, we know: - liquid water (a necessary condition to support life) continuously present since ~ 3.8 billion years ago (i.e. the age of the oldest sedimentary rocks) - . .but Earth’s climate has fluctuated from cold extremes to very warm conditions. What maintained Earth’s temperature within the range of liquid water? What produced these large climatic fluctuations? this means that temperature on Earth’s surface cannot have fluctuated beyond the freezing or boiling temperature of water Yet, geological evidence also indicates that the Earth’s climate has fluctuated from cold extremes when glaciers grew all the way to the tropics to warm extremes when polar ice totally melted. Climate on Earth is characterized by long periods of warm climate (no ice) separated by shorter episodes of cold climate (ice) During the Precambrian (prior to 544 Ma ago): -Conditions were warm during the first 2 billion years of Earth’s history -First glaciation 2.5-2.3 billion years ago. . (Huronian glaciation) -Followed by one billion years of warm climate -Second glaciation 800-600 Ma ago (“Snowball Earth”) Climate on Earth is characterized by long periods of warm climate (during which there is no ice accumulation on continents) separated by shorter episodes of cold climate (during which ice accumulated on continents as glaciers and ice sheets and on the surface of the ocean as sea ice) Conditions were warm during the first 2 billion years of Earth’s history (no evidence for glaciation on continents) Then, between 2.5 and 2.3 billion years ago, we find the first evidence for extensive glaciation (the “Huronian” glaciation, so called because the geological evidences were found in rocks near Lake Huron) That was followed by more than 1 billion years of warm climate before a second and very large glaciation event appeared during the Late Proterozoic (between ~ 800 Ma and ~ 600 Ma ago) called the snowball earth .. Earth’s climate warmed up and ice disappeared as we entered the Phanerozoic .. glaciations during the Permo-Caboniferous (~ 300 - ~ 270 Ma ago) .. and the Quaternary (last ~ 2 Ma) Then again, the Earth’s climate warmed up and ice disappeared as we entered the Phanerozoic eon. Warm climate persisted until the Permo-Carboniferous glaciations (~ 300 - ~ 270 Ma ago). This was followed again by warm climate until glaciation reappeared, particularly during the Quaternary (i.e. the last ~ 1.8 Ma when climate started to shift periodically between cold ice ages and warm interglacial periods
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Factors affecting the long-term evolution of climate on Earth “Faint Young Sun” paradox. . • Sun is growing in size and becoming hotter with time. . • 4.5 billion years ago, the Sun was 30% dimmer than today.
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This note was uploaded on 03/20/2010 for the course EOSC 116 taught by Professor Randell during the Winter '09 term at The University of British Columbia.

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PPT13 - Long Term Climate Evolution - Long-Term Climate...

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