This result has been at least half-expected ever since the ‘revision’ of sunspot numbers was announced. The phrase ‘desired outcome’ springs to mind.
The Sunspot Number is a crucial tool used to study the solar dynamo, space weather and climate change, reports Phys.org. 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.
The two methods of counting the sunspot number—the Wolf Sunspot Number and the Group Sunspot Number—indicated significantly different levels of solar activity before about 1885 and also around 1945. With these discrepancies now eliminated, there is no longer any substantial difference between the two historical records.
The new correction of the sunspot number, called the Sunspot Number Version 2.0, led by Frédéric Clette (Director of the World Data Centre [WDC]-SILSO), Ed Cliver (National Solar Observatory) and Leif Svalgaard (Stanford University, California, USA), nullifies the claim that there has been a Modern Grand Maximum.
Full Phys.org report: Corrected sunspot history suggests climate change not due to natural solar trends.
Note: the ‘after’ version of the sunspots graphic appears in the above link.