Note: See also the 1997 regime change in global climate data by the same method, here
I’m happy to report that something I recognized and reported back in 2008 related to solar data has been independently confirmed by another source, and was a surprise when it showed up in my inbox two days ago.
Readers may recall that for some time I’ve been pointing out a strange anomaly in the Solar Geomagnetic Index that occurred in October 2005. In a story I wrote on Feb 13th, 2008 titled Where have all the sunspots gone? I plotted the Ap data and pointed out the event.
I wrote then:
What is most interesting about the Geomagnetic Average Planetary Index graph above is what happened around October 2005. Notice the sharp drop in the magnetic index and the continuance at low levels.
This looks much like a “step function” that I see on GISS surface temperature graphs when a station has been relocated to a cooler measurement environment. In the case of the sun, it appears this indicates that something abruptly “switched off” in the inner workings of the solar dynamo. Note that in the prior months, the magnetic index was ramping up a bit with more activity, then it simply dropped and stayed mostly flat.
Since then, we’ve seen announcements like this:
“If we are right, this could be the last solar maximum we’ll see for a few decades,” Hill said. “That would affect everything from space exploration to Earth’s climate.”
See the official press release here – “All three of these lines of research to point to the familiar sunspot cycle shutting down for a while.”
Dr. Sam Outcalt : Emeritus Professor of Physical Geography, University of Michigan sent me this graph two days ago, showing his application of Hurst Rescaling to the Ap Solar Magnetic Index data. Using that method, he has independently identified the “step function switch off” I reported in Feb 2008:
The major regime transition is at the maximum of the integral at 2005.71, which corresponds to October 2005, the same date I identified.
Clearly the sun entered into a magnetic funk then, and has yet to come out of it.
We live in interesting times.
For more on Hurst ReScaling, see this paper: SIO_HurstReScale
UPDATE: As I expected he would, Dr. Leif Svalgaard takes exception to this characterization of the identification of October 2005 being a regime changepoint, saying:
While I agree that the sun is going quiet, the ‘step change’ is spurious. It is mainly due to a sporadic, single magnetic storm in September 2005: http://hirweb.nict.go.jp/sedoss/solact3/do?d=2005%2c09%2c04 and here is the next rotation: http://hirweb.nict.go.jp/sedoss/solact3/do?d=2005%2c10%2c01 You can find many such steps.
Such step changes happens all the time: http://www.leif.org/research/Ap-1844-now.png They are just weather, not climate.
I don’t think his analogy holds promise, because after the step change the “climate” of the solar dynamo stayed low, and then produced the lowest value in the record going back to 1844. See Leif’s graph (click to enlarge) which I’ve annotated:
While this is akin to the sustained drop starting in early 1871, clearly this was something new in the entire record.If we use smoothing to remove what Leif describes as weather noise, and magnify, we can see how this looks to be unique in the last century of data:
While it could be argued that this was a “weather” event, the facts remain that:
- In the 14 months prior to Oct 2005, the Ap index was on the rise
- It was a very sharp drop spanning a little over a month.
- It has not recovered to the average values in the preceding 14 months since then.
- Weather events are usually short term dynamics. The 2 rotation periods of the sun Leif refers to aren’t capable of maintaining the step change for the years following October 2005.
- Following the event, the Sun produced the lowest Ap value in the record in Dec 2008.
- Projections by others, including Livingston, suggest the sun has entered into a quiet magnetic state.
While I defer to Dr. Svalgaard’s overall superior knowledge on the dynamics of sun, and agree there are many sharp transitions in the Ap record, this looks to me to be a step change event of merit based on the factors listed above. I’ve yet to see a fully convincing explanation that this was a spurious event rather than a regime changepoint. But, I remain open to seeing such an explanation.