12 Jun 2010

At June 10th ... a connection has been made between La Nina sea surface temperatures in the central Pacific Ocean and drought in western Europe and the SW region of North America and Mexico, in a paper published by Geophysical Research Letters. El Nino's affect weather systems, it is thought - and therefore so too must La Nina's. They are a fashionable subject amongst meteorologists and climate scientists, and a central feature of the thermohaline system - shifting warm, or cold surface water around the planet. In this instance fossil coral has been used to reconstruct sea surface temperatures between 1320 to 1460AD in order to simulate late medieval climate conditions. The results were then compared with other proxy data - such as tree rings. During those 142 years they found the sea surface temperature dropped by only one tenth of one degree yet the researchers make the claim this was enough to cause arid conditions in North America and in Europe. For example, cliff dwellings in Utah occupied by Anasazi were abandoned 600 years ago without explanation - and drought is usually blamed. In western Europe, in contrast, the period 1315-1320 was extremely wet and crops rotted in the fields leading to severe famine among peasant populations. The research appears to want to blame La Nina for the drought - and famine in Europe, but it appears to forget some interesting tree ring anomalies in the 14th century and the outbreak of plague that dessimated the rich as well as the peasants. It is not suspected the plague also affected the Americas - it cannot have done unless it had an origin in the atmosphere. For a different take on the 14th century see Mike Baillie, New Light on the Black Death, Tempus:2006. He also notes a cooling of North Atlantic surface waters in the 1320s and 1330s, coinciding with an abrupt downturn in European oak growth. Baillie also brings in volcanoes, drought famine and floods in China, locusts, famine and pestilence, more floods in China, uncommon atmospheric phenomena and frequent thunderstorms across France and Germany, earthquakes in China and subterranean thunder, floods in Germany with tectonic disturbance and fiery meteors etc. Clearly, to solely concentrate on La Nina for what happened to the Anasazi can only be due to the focus of the research - on modern climate change. Funding demanded an input on modern climate science theory - and this is what it amounts to. In fact, we are none the wiser in finding out what happened in the 14th century - but they have managed to slew the data and show that one tenth of one degree is important - for global warming as much as global cooling. Baillie, page 113, places the Anasazi abandonment of their settlements squarely between 1333-1347, a calamitous period around the world - nothing to do with drought (although it may have been one factor).