Geography and Paleoclimate

Paleoclimate has had a major effect in shaping not only physical geography but also biodiversity in different parts of the Earth. This is noticeable in even relatively recent geological timescales. For instance, Coleogyne ramosissima, or the plantbrush, became isolated and evolved as very different populations over the last 12,000 years due to glaciation that occurred in the Last Glacial Maximum.[1]

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Paleoclimate researchers incorporate ice cores and sea cores to understand global oceanic circulation, which drives major climate systems in the present and past.[2] In terrestrial regions, speleothems, or karstic (limestone, dolomite and other soluble rocks) deposits such as stalagmites and stalactites, have been used to reconstruct past climate. These deposits capture small particles of water and oxygen and carbon isotopes that can then be studied for climatic change through the ratio of isotopes.

In the last two decades, this has revolutionized our understanding of paleoclimate in terrestrial environments, as researchers can also date speleothems precisely using Uranium series dating. Climate data from speleothems and other sources have shown major changes in Earth’s climate happening at the beginning of the Holocene (about 11,500 years ago) that included much wetter conditions in regions such as Europe and the Middle East.[3] This change in climate likely gave rise to agriculture, as grasses and different types of plants expanded in regions such as around the Mediterranean.

Understanding past climate change also provides scientists with understanding how future climate change may occur. For instance, areas affected by major droughts in the past are studied to show similar variables, such as increased volatility in rainfall, that occur in the same regions today and how trends in rainfall suggest the likelihood if a given region is more likely to climatically change in the future.[4] Similar variables affecting past climate, including higher greenhouse emissions, have been demonstrated to have similar effects for modern and future climates. Ice core data trap small amounts of the atmosphere in the past; water can be used to study oxygen isotopic composition to show how rapidly global temperatures changed as CO2 and other greenhouse gasses fluctuated in different periods.[5] In effect, such past physical changes are used to model future climatic change as scientists now have a stronger understanding of the relationship between isotopic composition and greenhouse gasses in the atmosphere.

Simulated climate for each of four time periods for peak summertime (July to August and January to February means) surface air temperature , from left to right: present day (Modern), 130,000 years ago (anomalies from present day, D LIG), 2100 A.D. (the time atmosphere reaches three times preindustrial CO2 levels, climate anomalies from present day, D AD 2100), and 2130 A.D. (four times preindustrial CO2 levels, climate anomalies from present day, D AD 2130). From Overpeck et. al, 2006.

Simulated climate for each of four time periods for peak summertime (July to August and January to February means) surface air temperature , from left to right: present day (Modern), 130,000 years ago (anomalies from present day, D LIG), 2100 A.D. (the time atmosphere reaches three times preindustrial CO2 levels, climate anomalies from present day, D AD 2100), and 2130 A.D. (four times preindustrial CO2 levels,
climate anomalies from present day, D AD 2130). From Overpeck et. al, 2006.

References

[1] For more on the planbrush’s genetic changes due to glaciation, see:  Richardson, Bryce A., and Susan E. Meyer. 2012. “Paleoclimate Effects and Geographic Barriers Shape Regional Population Genetic Structure of Blackbrush ( Coleogyne Ramosissima : Rosaceae).” Botany 90 (4): 293–99. doi:10.1139/b2012-002.

[2] For more on ice cores and sea cores, see:  Gornitz, Vivien, ed. 2009. Encyclopedia of Paleoclimatology and Ancient Environments. Encyclopedia of Earth Sciences Series. Dordrecht, Netherlands ; New York: Springer.

[3] For more on climatic change in Europe and Middle East due to speleothem data, see:  Mayewski, Paul A., Eelco E. Rohling, J. Curt Stager, Wibjörn Karlén, Kirk A. Maasch, L. David Meeker, Eric A. Meyerson, et al. 2004. “Holocene Climate Variability.” Quaternary Research 62 (3): 243–55. doi:10.1016/j.yqres.2004.07.001.

[4] For more on using paleoclimate in understanding future climate change, see:  Overpeck, J. T. 2006. “Paleoclimatic Evidence for Future Ice-Sheet Instability and Rapid Sea-Level Rise.” Science 311 (5768): 1747–50. doi:10.1126/science.1115159.

[5] For more on greenhouse gasses and ice cored data, see:  Raynaud, D., J-M Barnola, J. Chappellaz, T. Blunier, A. Indermühle, and B. Stauffer. 2000. “The Ice Record of Greenhouse Gases: A View in the Context of Future Changes.” Quaternary Science Reviews 19 (1-5): 9–17. doi:10.1016/S0277-3791(99)00082-7.

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