What happened to the sunspots?

Solar astronomers modernized the entire 405-year sunspot history for the first time since its creation in 1849; so what does it mean?

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Giant sunspot group AR1944 seen in January of 2014. Credit: NASA/SDO

AUSTIN, Texas, July 9, 2015 – On June 30, 2015 the globally recognized maximum for the current 11-year sunspot cycle was 81.9. On July 1, 2015 that number suddenly leaped all the way up to 116.4!

Stranger still, the current cycle (Cycle 24) fell from being the 7th weakest sunspot maximum since 1749 to being the 4th weakest sunspot maximum. Cycle 24’s sunspot number jumped by 30 percent, yet its ranking dropped by three places. How can that be?

After a 4-year study, solar astronomers modernized the entire 405-year sunspot history for the first time since its creation in 1849. Now, count tallies more closely match the actual tallies of today’s observers using modern technology.

Current 11-year cycle (Cycle 24) dropped from 7th to 4th weakest in new revision. Credit: Steve Davidson, WDC/SILSO data
Current 11-year cycle (Cycle 24) dropped from 7th to 4th weakest in new revision. Credit: Steve Davidson, WDC/SILSO data
Sunspot revisions shows higher counts and other changes. Credit: Steve Davidson, WDC/SILSO data
Sunspot revisions shows higher counts and other changes. Credit: Steve Davidson, WDC/SILSO data

The most obvious change is that the sunspot counts have increased across the 405-year sunspot timeline. The increase was made possible because of a meticulous review of the entire historical record coupled with modern data from other solar activity parameters, calibrated with sunspot counts.


Besides having higher sunspot tallies, there are other subtle changes that show up.

For example, the 11-year cycle shown above, Cycle 23, formerly had a double peak where the first peak was higher than the second. But in the new version, the second peak is now higher than the first. Given the reversed double peak, not only is Cycle 23’s maximum even higher than it otherwise would be, but it’s in a different year, too. Changes like that occur throughout the sunspot time series.

What all these changes mean for our physical understanding of the sun is unknown, but there are two interesting cycle changes directly related to long-term climate change.

Current 11-year cycle ranks between Cycle 5 and Cycle 12. Credit: Steve Davidson, WDC/SILSO data
Current 11-year cycle ranks between Cycle 5 and Cycle 12. Credit: Steve Davidson, WDC/SILSO data

The current 11-year cycle looks a lot closer to Cycles 5 and 12 than any others. It now fits between Cycle 12 and Cycle 5. Cycle 5 is the first entering into a period of three successive weak solar cycles called the Dalton Minimum, 200 years ago. Cycle 12 is the first entering into another series of three exceptionally weak cycles in the late 1800s.

The current solar cycle shares these unique qualities with the other two:

  • All have exceptionally weak sunspot maximums
  • All have double-peaked maximums
  • Unusual for maximums, the 2nd peak of each is higher than the first

Cycle 5 and Cycle 12 share these additional characteristics:

  • Both were followed by extended minimums
  • Both were followed by two more exceptionally weak cycles
  • During both multi-cycle activity minimums, earth’s global temperature fell

The current 11-year cycle we are experiencing most closely resembles Cycle 12. Cycle 12 was at the beginning of a cooling trend that lasted from 1880 to 1915. The International Panel on Climate Change (IPCC) temperature records show that earth’s global temperature decreased by 0.3°C during that time.

Early forecasts suggest that the next cycle, Cycle 25, will be even weaker than the current cycle. Should that happen then earth may enter a period more like the Dalton Minimum, which is believed colder than 1890 to 1915.

As it is, since 1998, the earth has barely warmed. Lower troposphere temperature increase is less than +0.1°C. That is literally undetectable by most thermometers, much less felt by humans. Its rise is less than the mathematical level of statistical significance. That means, mathematically speaking, earth’s temperature hasn’t risen over the last 17 years.

Earth’s temperature will rise less than 1°C over the rest of this century at its current pace.

Should solar history repeat itself, and indicators are that it will, there likely will be an extended period of low solar activity over the next 11-year cycle and beyond.

The good news is that with the slowdown in earth’s temperature rise and prospects for decades-long cooling to come, it’s unlikely the dreaded 2°C threshold will be exceeded any time soon, even with human greenhouse gas emissions continuing to increase.

The best news of all is that it means hasty, and expensive, decisions to curb CO2 emissions don’t have to be made immediately to meet an arbitrarily scheduled deadline of December 2015 for the Paris climate summit. Radical climate change solutions appear unnecessary at this time.

 

 

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