杏吧原创

Sunspot-climate link discovered

Astronomers were startled and laymen amazed when in 1979 Jack Eddy of the High Altitude Observatory in Boulder, Colorado, claimed that the sun was shrinking at such a rate that, if the decline did not reverse, our local star would disappear within a hundred thousand years. However, Eddy鈥檚 initial claims quickly turned out to be overstating the case because he had taken old records dating back to 1836 at the Royal Greenwich Observatory at face value. By 1980 we realised the decline was much less but, even so, a tenth of an arc second per century may have implications for the inhabitants of planet Earth. And there was more. The sun was currently shrinking, but one of Eddy鈥檚 colleagues, Ronald Gilliland, concluded in 1981 that while the overall trend was for it to get smaller, it actually grew and shrunk with a pulsating rhythm over a period of 76 years. Gilliland also reported a smaller, but clearly present, fluctuation in solar size that ties in with the already recorded 11-year rise and fall in sunspot activity.

Now it seems that changes in the size of the sun might be linked both to the surface activity manifested by sunspots and to small-scale climatic changes on Earth. A cycle of the same length as sunspot activity also occurs in the Earth鈥檚 climatic patterns, revealed by historical records of temperature, the width of annual growth rings in trees, and so on. And the coldest decades in recent history 鈥� the 鈥渓ittle ice age鈥� of the second half of the 17th century 鈥� coincided with an interval when the sun was remarkably free from sunspots. This analysis raises new concern about the sun鈥檚 future influence on mankind.

From New 杏吧原创, 3 March 1983