Climate Chronicle, covering the years 2300 and extracted specialist, University of Pittsburgh (USA) at the bottom of Lake Laguna Pumakocha (Peru), showed that warming in the northern hemisphere, leading to severe water shortages in densely populated tropical regions of the world, for the summer monsoons become drier.
Scientists note that the information in their possession two meter core contains the most detailed geochemical data on the oscillations of the tropical climate, ever fall into the hands of specialists. In combination with other information, it indicates that at the turn of the XX century. rainfall during the summer monsoon in South America began to decline in the most radical way in the whole grip of Punch story — that is, from 300 BC. e. If monsoon moisture will continue to decline at the same rate, a vast strip of the planet headed for disaster.
Overall core showed regular fluctuations in rainfall from 300 BC. e. at 900, with the heaviest rains about 550 to about 900, began a severe drought. Particularly severe drought held from 1000 to 1040 This period corresponds with the loss of a number of Native American cultures, including the Tiwanaku and Wari, existed in what is now Bolivia, Peru and Chile.
After 1300 monsoon, however, began to fill the South American tropics. The wettest period lasted from about 1500 to 1750 at this time, came the so-called Little Ice Age — reduction in average global temperature. About 1820 for a short time to install the dry, but really less precipitation began in 1900
The basis of the findings — the study content in the core of the oxygen isotope? 18O. Its concentration is low in the wet season. These data are broadly consistent with the analysis of the cave Kaskayunga (Peru) and Kelkkaya ice cap in the Andes.
In addition, researchers have established a link between the rainy season and the temperature of the Northern Hemisphere, comparing the data with a core of tropical convergence zone — the band of storms near the equator, where there are winds (trade winds) of the northern and southern hemispheres. Experts have concluded that the northern warming (as now) leads to a shift of the zone — the main source of the monsoon — the north.
History of tropical convergence zone is restored by measuring the titanium concentration in marine sediments. The high concentration of titanium in the bottom of Cariaco Basin off the north coast of Venezuela has shown that this area is in the far north at a time of the greatest drought in South America, that is 900-1100 years. Conversely, during the Little Ice Age from 1400 to 1820 it was located south of the equator.
Concentration?18O in the core Pumakochi overlay relevant data Kaskayunga caves (red) and the ice cap Kelkkaya (blue).
Concentration?18O Pumakochi in the core is consistent with the solar radiation, the concentration of titanium in the Cariaco Basin and the average annual temperature in the northern hemisphere and the North Atlantic.