As Sun is expected to experience a period of lower activity, the Earth will receive less heat and thus will cool. Earth's climate is determined mainly by the Sun's activity and by the small changes in Earth's orbit. The effects of other factors, such as the greenhouse gases, are small relative to these cosmic events.

A Russian astronomer, Khabibullo Abdusamatov of the Pulkovo Astronomic Observatory in St. Petersburg, reported on Monday that the global warming experienced in the 20th century was mainly caused by an increased solar activity. According to him, this increased solar activity will reach its peak in six of seven years from now, after which the temperatures will start to drop.

Abdusamatov said there will be a massive solar output decline between around 2035 and 2045 which will correspond to a mini Ice Age on Earth.

"Dramatic changes in the Earth's surface temperatures are an ordinary phenomenon, not an anomaly", he said, "and result from variations in the sun's energy output and ultraviolet radiation."

This is also supported by a recent mapping of North American glacial history which has shown that in the last 10 000 years glaciers have gone up and down many times. In other words, there were large climatic variations.

The Northern Hemisphere's most recent cool-down period occurred between 1645 and 1705. Dubbed the Little Ice Age, it left canals in the Netherlands frozen solid and forced people in Greenland to abandon their houses to glaciers.