"Long before it's in the papers"
July 11, 2015


Scientific dissenters predict “mini ice age” in 2030s

July 11, 2015
Courtesy of the Royal Astronomical Society
and World Science staff

A new mod­el of so­lar ac­ti­vity cy­cles pre­dicts that the Sun’s sur­face will be un­usu­ally calm in the 2030s—con­di­tions that last oc­curred four cen­turies ago and co­in­cid­ed with a “mini ice age.”

The sci­en­tists be­hind the mod­el in­deed pre­dict a si­m­i­lar cold spell, but only if they’re right about some­thing else too: that so­lar, and not hu­man, ac­ti­vity is caus­ing glob­al warm­ing to­day. Most cli­ma­tol­o­gists be­lieve the op­po­site.

Montage of im­ages of so­lar ac­tiv­i­ty be­tween Au­gust 1991 and Sep­tem­ber 2001. (Cred­it: Yohkoh/ISAS/Lockheed-Martin/NAOJ/U. Toky­o/­NA­SA)

The reduced so­lar ac­ti­vity would oc­cur ei­ther way, but it would­n’t out­weigh the ef­fects of a strictly hu­man-caused glob­al warm­ing, re­search­er Val­en­ti­na Zhar­ko­va of North­um­bria Uni­vers­ity in the U.K. wrote in an e­mail. In that case a mini ice age would­n’t oc­cur.

“Only time will show” what happens, she added.

Zhar­kova pre­sented the new re­search on July 9 at the U.K.’s Na­t­ional As­tron­o­my Meet­ing in Llan­dud­no, Wales.

Zharkova and col­leagues ar­gue that so­lar ac­ti­vity is the real cause of glob­al warm­ing, partly on grounds that re­cent warm­ing has al­so af­fect­ed oth­er plan­ets, where clearly no peo­ple live. “Si­m­i­lar glob­al warm­ing ef­fects were ob­served on Mars (melt­ing po­lar caps),” Zharkova wrote.

Re­gard­less of their stance on warm­ing, Zhar­kova and col­leagues say their mod­el of the so­lar cy­cle is pro­duc­ing un­prec­e­dent­edly ac­cu­rate pre­dictions of ir­reg­u­lar­i­ties with­in the Sun’s 11-year heart­beat. The mod­el draws on so-called dy­na­mo ef­fects in two lay­ers of the Sun. 

A dy­na­mo ef­fect oc­curs when en­er­gy as­so­ci­at­ed with the flow of ma­te­ri­al with­in a star is con­vert­ed in­to mag­net­ic en­er­gy.

Pre­dic­tions from the mod­el sug­gest that so­lar ac­ti­vity will fall by 60 per­cent dur­ing the 2030s to con­di­tions last seen dur­ing a “mini ice age” that be­gan in 1645 and af­fect­ed Eu­rope and North Amer­i­ca. 

It is 172 years since a sci­ent­ist first spot­ted that the Sun’s ac­ti­vity varies over a cy­cle last­ing around 10 to 12 years. But eve­ry cy­cle is a lit­tle dif­fer­ent and none of the mod­els of causes to date have fully ex­plained fluctua­t­ions. Many so­lar phys­i­cists have at­trib­ut­ed the cy­cle to a dy­na­mo caused by con­vect­ing, or churn­ing, flu­id deep with­in the Sun. 

Now, Zharkova and her col­leagues have con­clud­ed that adding a sec­ond dy­na­mo, close to the sur­face, com­pletes the pic­ture with sur­pris­ing ac­cu­ra­cy.

“We found mag­net­ic wave com­po­nents ap­pear­ing in pairs, orig­i­nat­ing in two dif­fer­ent lay­ers in the Sun’s in­te­ri­or. They both have a fre­quen­cy of ap­prox­i­mately 11 years, al­though this fre­quen­cy is slightly dif­fer­ent, and they are off­set in time. Over the cy­cle, the waves fluc­tu­ate be­tween the north­ern and south­ern hemi­spheres of the Sun. Com­bin­ing both waves to­geth­er and com­par­ing to real da­ta for the cur­rent so­lar cy­cle, we found that our pre­dictions showed an ac­cu­ra­cy of 97 pe­rcent,” said Zharkova.

She and her col­leagues de­rived their mod­el us­ing a tech­nique called “prin­ci­pal com­po­nent anal­y­sis” of mag­net­ic field ob­serva­t­ions from the Wil­cox So­lar Ob­serv­a­to­ry in Cal­i­for­nia. They ex­am­ined three so­lar cy­cles’ worth of mag­net­ic field ac­ti­vity, co­vering the pe­riod 1976-2008. They also com­pared their pre­dictions to av­er­age sun­spot num­bers, anoth­er strong mark­er of so­lar ac­ti­vity. All the pre­dictions and ob­serva­t­ions closely matched, they said.

Look­ing ahead to the next so­lar cy­cles, the mod­el pre­dicts that the pair of waves be­comes in­creas­ingly off­set dur­ing Cy­cle 25, which peaks in 2022. Dur­ing Cy­cle 26, which co­vers the dec­ade 2030-2040, the two waves will be­come ex­actly out of synch, sig­nif­i­cantly re­duc­ing so­lar ac­ti­vity.

“The two waves ex­actly mir­ror each oth­er – peak­ing at the same time but in op­po­site hemi­spheres of the Sun,” she said. As a re­sult, “they will nearly can­cel each oth­er. We pre­dict that this will lead to the prope­rties of a ‘Maun­der min­imum’,” a pe­riod of min­imal sun­spot ac­ti­vity such as was seen with the mini ice age.

* * *

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A new model of solar activity cycles predicts that the Sun’s surface will be unusually calm in the 2030s—conditions that last occurred four centuries ago and coincided with a “mini ice age.” The scientists behind the model indeed predict a similar cold snap, but only if they’re also correct about something else: that solar, and not human, activity is causing global warming today. Most climatologists believe the opposite. The low solar activity would occur either way, but it wouldn’t outweigh the effects of a strictly human-caused global warming, said researcher Valentina Zharkova of Northumbria University in the U.K. in an email. In that case a mini ice age wouldn’t occur. “Only time will show” which scenario unfolds, she added. Zharkova presented the new research on July 9 at the U.K.’s National Astronomy Meeting in Llandudno, Wales. Zharkova and colleagues argue that solar activity is the real cause of global warming, partly on grounds that recent warming has also affected other planets, where clearly no people live. “Similar global warming effects were observed on Mars (melting polar caps),” Zharkova wrote. Regardless of their stance on warming, Zharkova and colleagues say their model of the solar cycle is producing unprecedentedly accurate predictions of irregularities within the Sun’s 11-year heartbeat. The model draws on so-called dynamo effects in two layers of the Sun. A dynamo effect occurs when energy associated with the flow of material within a star is converted into magnetic energy. Predictions from the model suggest that solar activity will fall by 60 per cent during the 2030s to conditions last seen during a “mini ice age” that began in 1645 and affected Europe and North America. It is 172 years since a scientist first spotted that the Sun’s activity varies over a cycle lasting around 10 to 12 years. But every cycle is a little different and none of the models of causes to date have fully explained fluctuations. Many solar physicists have attributed the cycle to a dynamo caused by convecting, or churning, fluid deep within the Sun. Now, Zharkova and her colleagues have concluded that adding a second dynamo, close to the surface, completes the picture with surprising accuracy. “We found magnetic wave components appearing in pairs, originating in two different layers in the Sun’s interior. They both have a frequency of approximately 11 years, although this frequency is slightly different, and they are offset in time. Over the cycle, the waves fluctuate between the northern and southern hemispheres of the Sun. Combining both waves together and comparing to real data for the current solar cycle, we found that our predictions showed an accuracy of 97 percent,” said Zharkova. She and her colleagues derived their model using a technique called “principal component analysis” of magnetic field observations from the Wilcox Solar Observatory in California. They examined three solar cycles’ worth of magnetic field activity, covering the period from 1976-2008. In addition, they compared their predictions to average sunspot numbers, another strong marker of solar activity. All the predictions and observations were closely matched, they said. Looking ahead to the next solar cycles, the model predicts that the pair of waves becomes increasingly offset during Cycle 25, which peaks in 2022. During Cycle 26, which covers the decade 2030-2040, the two waves will become exactly out of synch, significantly reducing solar activity. “The two waves exactly mirror each other – peaking at the same time but in opposite hemispheres of the Sun,” she said. As a result, “they will nearly cancel each other. We predict that this will lead to the properties of a ‘Maunder minimum’,” a period of minimal sunspot activity such as was 370 years ago, she added.