Africa and the Ice Age threat (5)

IN any event, the Andean/Saharan (460 to 430 M.Y.A.) followed the Cryogenian, Then came the Karoo Ice Age (360 to 260 M.Y.A.), which is name for the area, in South Africa, where geologists found the glacial debris that confirmed the icing episode.The last great glacial event, the Pleistocene-Quaternary, started 2.58 M.Y.A. and, some geologists argue, continues. Despite 11,700 years of warm weather, the glaciers are still hibernating in the mountains and Polar Regions of Earth. So we remain, technically, in the Ice Age.The present interglacial may be ending'and another glacial about to begin. Is the projected Little Ice Age, then, a climatic harbinger of things to come'Probably not. The glaciers will eventually move out again, the Little Ice Age notwithstanding. It's a part of the natural rhythm of our planet ' a geological and climatic response to Earth's orbital motion and corresponding changes in its distance from and orientation to the Sun.Augmenting these orbital mechanisms (referred to as 'Milankovitch cycles') are what NOAA terms 'positive feedbacks' within Earth's climate system, which are 'very important in determining when glacial and interglacial periods occur'.Among them are the ice sheets themselves, NOAA scientists note, which reflect large amounts of solar radiation back into space and thus help lower surface temperatures. Added to this, are changes in Earth's ocean currents and in its vegetative cover.What is more, carbon-14 abundance and beryllium-10 ice core studies indicate that Little Ice Ages are possibly cyclic, with a 200-year periodicity: Whereas glacial and interglacial episodes have rhythmic patterns marked by thousands of years.Finally, true Ice Ages tend to be global in scope, with a prolonged frigid temperature regime. By contrast, Physical Geography.Net reports that, 'During the Little Ice Age, the average annual temperature of the Northern Hemisphere was about 1.0 degrees Celsius lower than today.'Indeed, Phillips estimates, 'a solar output decrease of 0.4'1.4 per cent could account for the occurrence of the Little Ice Age.'This amounts to a planetary cough, compared with the climatic transformations and geological upheavals of the Pliocene-Quaternary and the other great glacial episodes that came before it.
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