It is well known that global warming causes cooling of some parts of our wonderful planet. Shed light on the nature of this paradoxical mechanism could creator climate models Judah Cohen of the consulting firm Atmospheric and Environmental Research (USA) and his colleagues.
Global average temperature increases since the late XIX century. Fastest warming in the last forty years, and the Arctic is warming almost twice smarter than the rest of the world. Despite this, the winter in some parts of the Northern Hemisphere were colder — see, for example, southern Canada, the eastern United States and parts of northern Eurasia. In England, in December 2010, and at all recorded a record low temperature.
Helped to clarify the situation analysis of the oscillations of snow cover on land and at sea from 1988 to 2010. The researchers combined data from various sources in an attempt to assess the Eurasian snow cover and its influence on the temperature, and then extrapolate the results to other areas of the Northern Hemisphere.
First of all, the scientists struck by the massive loss of sea ice in the Arctic. Increasing the area of open water in the Arctic Ocean leads to increased evaporation and moisture of the atmosphere. Previous studies have linked the warmer summer months, with an increase in the autumn clouds over the ocean. What causes a heavy snowfall in Siberia in winter approaches. So, a group of Mr. Cohen found that snow cover in October has the greatest influence on the climate in the coming months.
The fact is that it enhances semi-permanent high pressure system called the Siberian anticyclone, which in turn has an impact on the climate phenomenon known as the Arctic Oscillation, directing cool air to the south — to the middle latitudes during winter.
"It is quite plausible," — says Anne Noeleen, a climate scientist at the University of Oregon (USA). On the causal link so far, but the correlation is obvious. "Northern Eurasia — the largest snow-covered land mass in the world," — emphasizes the expert, referring to the winter months. There is nothing strange in the fact that it has a serious impact on the climate of the Northern Hemisphere. Previous studies, she adds, have noted the connection between Siberian snow cover and climate in the North Pacific Ocean.
Our analysis suggests that such climatic cycles as Southern Oscillation (El Niño and La Niña), the Pacific Decadal Oscillation and the Atlantic mnogodekadnaya oscillation, can not explain the regional cooling trends in the Northern Hemisphere over the last couple of decades, and the trends of the Siberian snow . Perhaps it is time to turn autumn Siberian snow in climate models for more accurate predictions for the winter?