Sunspots 2015: Year of the decline

Giant solar flare on October 27, 2014. Credit/NASA SDO spacecraft

Solar maximum has passed. What climate effects will come next?  

Austin, January 4, 2015 – Solar maximum activity peaked in April 2014 at an exceptionally low 81.9 spots/day. Waning solar activity in 2015 will begin the long, inexorably journey towards solar minimum over the next half decade or so.

If solar physicists are correct, solar activity could be very low for several decades to come. How that will affect climate change is anyone’s guess, but low sunspot activity has already been identified by the United Nation’s International Panel on Climate Change (IPCC) as one of the main causes for the 15+ year “hiatus” from atmospheric global warming.

Solar max arrived in April 2014. Credit/Steve Davidson-SILSO data, Royal Observatory of Belgium, Brussels

The Royal Observatory of Belgium released December’s official monthly international sunspot numbers on January 1, 2015. Sunspots increased again in December, but the 13-month smoothed sunspot number that defines solar maximum declined for the 2nd month in a row. Given that solar maximum is a 13-month running average, no one knows maximum has been reached until at least seven months after the fact.

What does the downturn in solar activity mean for earth’s long-term climate change?

One legitimate comparison of the current situation on the sun is to a cold period on earth called the Dalton Minimum. It happened 200 years ago.

Current solar activity is similar to the Dalton Minimum. Credit/Steve Davidson using SILSO data

There were three declining solar cycles leading into the Dalton Minimum, just like now. The third exceptionally weak cycle had a rare higher secondary peak than its first when the Dalton was reached, just like now.

That cycle was followed by a decline to zero spots. The period of zero spots lasted nearly two years before another weak cycle occurred.

The match to current activity isn’t exact, but it’s eerily similar.

There is modern supporting evidence that the sun will have an exceptionally weak cycle next time, just like the Dalton.

Sunspots are becoming harder to see and weaker. Credit/Dr. Leif Svalgaard Research Page

Umbral intensity is a measure of how black the center of the average sunspot is compared to its surroundings. An intensity of 1 means the sunspot is invisible. Sunspots have been fading away since the late 1990s. In the last 3-4 years, though, the fading has leveled off.

Umbral magnetic field is a measure of the strength of the average sunspot, measured in Gauss. The lower the number, the weaker the sunspot. Strong magnetic fields are what cause giant solar flares and coronal mass ejections (CMEs) that dramatically affect earth. Sunspots cannot form with a field strength below 1,500 Gauss. In the last 3-4 years the decline in magnetic field strength has leveled off, too.

When this data was first published in 2011 it caused quite a stir among solar physicists. Some predicted sunspots would totally disappear after the current cycle ended. It doesn’t look like that will be the case after all. It looks like the next cycle, Cycle 25, will be another weak one, just like during the Dalton Minimum.

Reliable global temperature data does not extend further back than about 1850, fifty years after the Dalton. However, anecdotal evidence suggests there were very cold winter temperatures in the northern hemisphere during that time period.

The current sunspot cycle most closely matches Cycle 12, which peaked in 1883. That one is within reliable global temperature records.

The current solar cycle is best matched to Cycle 12. Credit/Steve Davidson using SILSO data

Both Cycle 12 and the current cycle have a rare secondary peak higher than the first. That has got to mean something.

According to IPCC data, the period of the 1880s to the early 1900s was characterized by a general decline in earth’s global atmospheric temperature.

1880-1910 cooling trend corresponds to low sunspot activity. Source/IPCC AR5 Report

Cycle 12 and the two cycles following it were exceptionally weak cycles leading into the early 1900s. It corresponded to declining global temperatures. Coincidence? Not likely.

Conclusions

Solar sunspot maximum was reached in April of 2014. That did not become known until recently because solar max is computed as a 13-month running average. You can’t know it has been reached until at least seven months after the fact. There have been two months of decline since then, so it is reasonably certain the maximum was finally reached. As it is, it was over two years later than originally predicted.

If the current cycle follows past solar behavior then 2015 will see a steep decline in solar activity as it progresses toward solar minimum in the next five years or so.

The current cycle (Cycle 24) has strong similarities to both the Dalton Minimum and Cycle 12 that peaked in 1883. Both time periods are associated with cold earth temperatures. Cycle 12 is more meaningful because it is supported by current United Nations IPCC data.

That being the case, it’s time to start thinking about breaking out the cold weather gear.

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