Some researchers have proposed that human influences on climate began earlier than is normally supposed see Early anthropocene for more details and that major population declines in Eurasia and the Americas reduced this impact, leading to a cooling trend. William Ruddiman proposed that somewhat reduced populations of Europe, East Asia, and the Middle East during and after the Black Death caused a decrease in agricultural activity. He suggests reforestation took place, allowing more carbon dioxide uptake from the atmosphere, which may have been a factor in the cooling noted during the Little Ice Age.
Dull and Nevle calculated that reforestation in the tropical biomes of the Americas alone from accounted for net carbon sequestration of Pg . Brierley conjectured that European arrival in the Americas caused mass deaths from epidemic disease, which caused much abandonment of farmland, which caused much return of forest, which sequestered greater levels of carbon dioxide. It has been speculated that increased human populations living at high latitudes caused the Little Ice Age through deforestation.
The increased albedo due to this deforestation more reflection of solar rays from snow-covered ground than dark, tree-covered area could have had a profound effect on global temperatures.
Spontaneous fluctuations in global climate might explain past variability. It is very difficult to know what the true level of variability from internal causes might be given the existence of other forcings, as noted above, whose magnitude may not be known. One approach to evaluating internal variability is to use long integrations of coupled ocean-atmosphere global climate models.
They have the advantage that the external forcing is known to be zero, but the disadvantage is that they may not fully reflect reality. The variations may result from chaos -driven changes in the oceans, the atmosphere, or interactions between the two. From Wikipedia, the free encyclopedia. For the most recent period much colder than present and with significant glaciation, see Last glacial period.
A period of cooling after the Medieval Warm Period that lasted from the 16th to the 19th century. Main article: Milankovich cycles. Main article: Solar variation.
Barbara Bray. Garden City, NY: Doubleday. Bibcode : TrAGU.. Matthes described glaciers in the Sierra Nevada of California that he believed could not have survived the hypsithermal ; his usage of "Little Ice Age" has been superseded by " Neoglaciation ".
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Climate - El Niño/Southern Oscillation and climatic change | taupamatantfur.ga
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Natural Climate Cycles
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Changes in atmospheric constituents and in radiative forcing. In: Solomon, S. Jump to Navigation Skip to main content. For example: Changes in land and ocean floor topography have had major influences on global climate at time scales of 50 million to million years. Ice ages correspond closely with Milankovitch cycles.
Since glaciers can only form over land, ice ages only occur when landmasses cover the polar regions. Therefore, Milankovitch cycles are also connected to plate tectonics. Greenhouse gases in the atmosphere trap the heat that radiates off the planet's surfaces. Therefore, a decrease in greenhouse gas levels lowers the average air temperature.
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An increase in greenhouse gases raises air temperature. Greenhouse gas levels have varied throughout Earth history. For example, CO 2 been present in Earth's atmosphere at concentrations less than parts per million ppm and more than 5, ppm. But for , years or more, CO 2 has never risen above ppm, during either glacial or interglacial periods. CO 2 levels are higher during interglacial than glacial periods Figure Greenhouse gases are added to the atmosphere by natural processes, like volcanic eruptions, and the decay or burning of organic matter.https://dayscathkino.tk
Causes of multidecadal climate changes
Greenhouse gases are also removed from the atmosphere when CO 2 is absorbed by plant tissue. When plants die and are turned into fossil fuels - coal, oil, natural gas - deep in the Earth, the CO 2 they hold is stored with them. Storing CO 2 in the ground removes the greenhouse gas from the atmosphere, lowering Earth's average temperature.