Revision to 400-year sunspot record makes current solar cycle weakest in 200 years

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Rare spotless day observed on July 18, 2014

A rare spotless day on the sun on July 17-18, 2014 triggered public speculation that an already stunted Cycle 24 was nearly over. Such is not the case. Defying the odds for so late in a sunspot cycle, another solar sunspot maximum was set last month. Another one is coming this month.

In other major news, a long needed revision to the 400-year sunspot record was proposed. It'll be the first change made to the sunspot record since it was first established by Rudolf Wolf back in 1849. The changes will affect long-term climate and other dependent scientific studies.

One effect of the proposal will be to reduce modern sunspot totals.

That will wipe out the so-called "Modern Maximum " and make the current sunspot cycle, Cycle 24, the weakest in 200 years.

Cycle 24 solar sunspot progression

After four straight months of steep declines in monthly sunspot counts, July reversed the trend and increased slightly.

The Royal Observatory of Belgium released July's average monthly sunspot count on August 1, 2014. Despite the mid-month spotless day, the sunspot number increased and it grew solar maximum again for the sixth straight month.

Extended periods of inactivity - like the Spörer, Maunder and Dalton minimums - were all accompanied by cooler earth temperatures. Conditions today mimic Cycles 3, 4 and 5 which marked the beginning of the Dalton Minimum .

Revising the 400-year sunspot record

The 400-year sunspot record is the longest continuously recorded daily measurement made in science. It's used in many scientific disciplines, including climate science studies. It hasn't been adjusted since Rudolf Wolf created it over 160 years ago.

Over the centuries errors have crept into the record, degrading its value for long-term studies. New data and discoveries now allow scientists to detect and correct errors. The first serious look back at the long-term record since Wolf in 1849 came without even a press release last month. It's a modestly titled new paper called "

Revising the Sunspot Number

" by Frédéric Clette, et al., submitted for publication to the journal

Solar and Stellar Astrophysics

on July 11, 2014.

Some outcomes of the new paper include:

• The so-called "Modern Maximum" disappears


• Sunspot activity is steady over the last 250 years


• Three detected "inhomogeneities" since 1880 are corrected


• Cycle 24 will become the weakest in 200 years

The new paper describes the current state of understanding of the long term record. It isn't a complete revision of the entire record, but a first level recalibration going back to 1749. The Royal Observatory of Belgium plans to release this and other revisions incrementally over time.

Solar physicist, Dr. Leif Svalgaard of Stanford University, organized a series of four workshops beginning in 2011 designed to review and revise the long term record. This new paper is the first fruit of that labor. Primarily, it removes "inhomogeneities" and brings the International Sunspot Number and newer Group Count record and solar magnetic history in sync.

Ultimately, Svalgaard seeks to extend the official record back to the early 1600s, before the Maunder Minimum. The paper outlines what needs to occur to make that happen.

For now the proposed revision stops at Wolf's 1749 starting point.

Conclusions

The sun continues to confound observers. Albeit exceptionally weak, Cycle 24 continues to set solar maximums each month long after its forecast peak of activity should have passed.

Dr. Svalgaard's

landmark physics-based 2004 paper

forecasting 75±8 for the Cycle 24 peak is spot on. Everyone else predicted higher numbers, some as high as 144. Back in 2004 he also said solar max would come in "~2011″.

By 2009 NASA revised their forecast saying solar max would be in mid-2013. Both are wrong. It hasn't arrive yet.

The newly proposed revisions to the sunspot record going back to 1749 will have some effect on global warming predictions. Exactly what that effect will be remains to be seen. Based on reduced solar activity, the smart money says the current 14-year "pause" in global warming will last for many more years to come, perhaps accompanied by some cooling.