According to the International Astronomical Union (7 August 2015), sunspot activity over the last 400 years has remained more or less stable and cannot, therefore, be responsible for global warming since the industrial revolution.
“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 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.”
“The apparent upward trend of solar activity between the 18th century and the late 20th century has now been identified as a major calibration error in the Group Sunspot Number. Now that this error has been corrected, solar activity appears to have remained relatively stable since the 1700s.”
Full article (Science Daily) here: