The Sunspot Number is a crucial tool used to study the solar dynamo, space weather and climate change. It has now been recalibrated and shows a consistent history of solar activity over the past few centuries. The new record has no significant long-term upward trend in solar activity since 1700, as was previously indicated. This suggests that rising global temperatures since the industrial revolution cannot be attributed to increased solar activity.
The analysis, its results and its implications for climate research were made public today at a press briefing at the International Astronomical Union (IAU) XXIX General Assembly, currently taking place in Honolulu, Hawaii, USA.
The Maunder Minimum, between 1645 and 1715, when sunspots were scarce and the winters harsh, strongly suggests a link between solar activity and climate change. Until now there was a general consensus that solar activity has been trending upwards over the past 300 years (since the end of the Maunder Minimum), peaking in the late 20th century—called the Modern Grand Maximum by some.
This trend has led some to conclude that the Sun has played a significant role in modern climate change. However, a discrepancy between two parallel series of sunspot number counts has been a contentious issue among scientists for some time.
