Doubts over climate change link to Sun’s activityUntil recently, scientists believed solar activity had been trending upward in the past three hundred years after a period known as the “Maunder Minimum” or “the little ice age”. Furthermore they also reported that from 1885 to 1945, there was a marked increase in the number of sunspots, which is commonly known as the Modern Grand Maximum.
As it happens, the authors of the review say it was always problematic to use the sunspot number as a single authoritative source. After that period, scientists used two separate methods to measure sunspot activity: the Wolf Sunspot Number and the Group Sunspot Number.
But in 1994 scientists began to question whether the WSN was an accurate method to build a reliable index of historical sunspot records.
So, a new counting method called the Group Sunspot Number (GSN) was created by Douglas Hoyt and Ken Schatten in 1994 and introduced in 1998.
This recalibration is a major step forward in studying solar activity as the sunspot number is the only direct record of the evolution of the solar cycle over centuries and is the longest scientific experiment still ongoing. Uncertainty loomed after they did a re-analysis of past records. This has become a contentious issue among scientists for some time.
As SILSO explains, the sunspot data set (which, courtesy of Galileo (the man, not the spacecraft), stretches back 400 years) was first collected into an index by Rudolph Wolf in 1849. During the Maunder Minimum there were scarce sunspots and the winters harsh.
“In other cases, sky-watchers were focused on making other solar observations, so if their notes do not mention sunspots this does not necessarily mean that none were present”, said a report in the journal Nature. Now that the error has been corrected, the researchers believe the data indicates solar activity has remained stable since the 1700s.
A new study conducted by researchers in the United States, however, has found no evidence of such solar activity culmination that occurred during the 20th century.
Zharkova’s prediction has been met with criticism from fellow scientists who study solar activity and climate change.
Now, researchers say that flaw has been eliminated and the sunspot counting method has been re-calibrated. “There has been nothing exceptional about the level of solar activity”, Dr. Clette told a meeting of the worldwide Astronomical Union in Honolulu, Hawaii.
The resulting new sunspot index called the Sunspot Number Version 2.0, which also includes the older historical data of the GSN, shows that solar activity has been constant over the past few centuries without any noteworthy long-term upward trends in solar activity since 1700.
“This suggests that rising global temperatures since the industrial revolution cannot be attributed to increased solar activity”, it added.
http://sentinelrepublic.com/doubts-over-climate-change-link-to-sun-s-activity/69971/
