It surely looks like the solar minimum has arrived, and it has done so far earlier than expected!
On Sunday NOAA posted its monthly update of the solar cycle, covering sunspot activity for March 2018. Below is my annotated version of that graph.
March 2018 was the least active month for sunspots since the middle of 2009, almost nine years ago. In fact, activity in the past few months has been so low it matches the low activity seen in late 2007 and early 2008, ten years ago when the last solar minimum began and indicated by the yellow line that I have added to the graph below. If the solar minimum has actually arrived now, this would make this cycle only ten years long, one of the shortest solar cycles on record. More important, it is a weak cycle. In the past, all short cycles were active cycles. This is the first time we have seen a short and weak cycle since scientists began tracking the solar cycle in the 1700s, following the last grand minimum in the 1600s when there were almost no sunspots.
The graph above has been modified to show the predictions of the solar science community. The green curves show the community’s two original predictions from April 2007, with half the scientists predicting a very strong maximum and half predicting a weak one. The red curve is their revised May 2009 prediction.
The graph [above], courtesy of the Sunspot Index and Long-term Solar Observations webpage (SILSO), will give you an idea how little activity occurred in March. There were only five days during the entire month where sunspots could be seen on the visible hemisphere of the Sun. We have not seen so little activity since 2009, when the Sun was in the middle of its sunspot minimum.
We could still see a recovery in sunspot cycle. Past cycles tended to ramp down slowly to solar minimum, not quickly as we have so far seen with this cycle. For example, look at sunspot activity during 2007 on the NOAA graph above. Though activity was dropping, throughout the year there were new bursts of activity, thus holding off the arrival of the minimum. It would not be surprising or unusual to see this happen now. […]
The big question remains: Are we about to head into a grand minimum, as happened during the Maunder Minimum in the 1600s? During that century there were practically no sunspots. Since it occurred immediately after the invention of the telescope, astronomers had no idea that the lack of sunspots were unusual and did not give it much attention. It wasn’t until the solar cycle resumed in the 1700s that they discovered its existence, and thus realized the extraordinary nature of the century-long minimum that had just ended. Unfortunately, it was over, and the chance to study it was gone.
Thus, if a new grand minimum is about to start, it will be a once-in-a-lifetime opportunity for today’s solar scientists. Not only will they will get to study the Sun as it behaves in a manner they have not seen before, they will be able to do it with today’s phalanx of space-based observatories. The chance to gain a better understanding of the Sun will be unprecedented.
Furthermore, the occurrence of a grand minimum now would help the climate field. We really do not know the full influence of the Sun’s solar cycles on the Earth’s climate. There is ample circumstantial evidence that it has a significant impact, such as the Little Ice Age that occurred during the last grand minimum, as well as the unusually cold climates that also matched past weak cycles, now, and also in the early 19th and 20th centuries. Studying a grand minimum with today’s sophisticated instruments could help measure precisely how much the Sun’s sunspot activity, or lack thereof, changes the climate here on Earth.