Climate see saw two million years ago

26 Dec 2012

At ... we learn that climate see saws are not just a feature of the most recent Ice Age but were happening in earlier epochs, even as long ago as two million years. This is where the lake sediments extracted from the area of the Olduvai Gorge in Tanzania have taken scientists - in search of the roots of human beings. For a period of roughly 200,000 years the climate oscillated between closed woodland and open savannah grassland - on five or six occasions. Each change is said to have occurred abruptly - in a geological sense of abruptness. In other words, the sediments show sharp points of change between tropical and savannah ecologies, without the exactness of supporting proxy data. So, this discovery is not being expanded to the whole of the Pleistocene - or the last two million years as a whole. However, if it was variable two million years ago, and likewise variable during the last 100,000 years, it is pretty likely it will have been variable in between - especially as it is being blamed on the Milankovitch cycle and changes in orbit as the Earth moves around the Sun. This is thought to cause the monsoon belt to move north or south, leading to drier or wetter climate, depending on where the research is aimed. However, it is never the less somewhat contradictory as the Milankovitch cycle is a slow process and the headline of the press release is that the changes were rapid - but there you are. The shift in monsoon belt as a consequence of Milankovitch is the fall-back position. Any other point of view would be catastrophic - and the catastrophism in the climate is just a future thing. The author of the paper sees it as evidence humans or proto-humans adapted to variable climatic situations - why didn't they just move with the monsoon rains. The animals did. The Ice Ages are of course associated with a general drying of the global environment - how else might all those deserts have developed in areas where there are no deserts today, or how might all that loess have been driven by the wind to pile up in such big heaps, especially in China, and why might equatorial regions today have been temperate on occasions over the last two million years - a variable climate. A variable climate but what caused the variability, Milankovitch theory or some other factor which was somewhat quicker and more rapid.