Tourists enjoy the warm weather on a beach in the Black Sea coast city of Varna, about 450 km (280 miles) northeast of the Bulgarian capital Sofia, June 25, 2008.
Austrian scientists found that 13,000 years to 19,000 years ago, there was no "real" summer on the Earth. At that time, the average temperature in summer was low and sharply volatile.
Kerstin Huber, a scientist of the Institute for Limnology, Austrian Academy of Sciences, pointed out in his latest academic report that, according to the analysis of the remnants of algae and pollen in the sediment of the Lange Lake, Carinthia, Austria, there was no summer in this area at that time, and the range of fluctuation reached nearly 8 degrees Celsius.
The report said, after the end of Ice age about 20,000 years ago, the temperatures on the Earth became warming. About 17,000 years ago, the Earth experienced a drastic cold spell which lasted nearly 2,500 years. Till 14,500 years ago, the temperatures increased again.
At that time, in the area of Lange Lake, "the average water temperature in summer had rapid change. In the warm time, it reached 18 degrees Celsius, while in the cold period, it was only 10 degrees Celsius. The atmospheric temperature in the region also showed a similar fluctuation."
As climate changes, it would directly affect the types of growing plants, such as shrubs, grasses and algae can survive in low-temperature condition, while trees and other plants are only suited to warmer weather.