Recent observations suggest the sun has entered a period of reduced activity, even though the opposite should be happening.
What are some of the possible ramifications of this change in cycle?
Staff Writer Seiji Tanaka attempts to shed light on this subject in Q&A format.
Question: What can be inferred by recent reports that the sun is entering a "period of hibernation"?
Answer: Some scientists believe temperatures on Earth are falling due to a weakening of the energy of light and magnetism reaching the Earth due to the sun's reduced activity.
Q: Is this the first time this has happened?
A: No, the Earth entered a "little ice age" around 1650 and again around 1800. It is believed both developments were created by the sun entering into a period of hibernation.
Q: What do you mean by little ice age?
A: Solar activity weakened for between 30 and 70 years. Illustrations from the 17th century show the River Thames in London frozen over. In Japan, cherry blossoms bloomed later than usual in Kyoto. In Japan, temperatures were about 2 degrees lower than in the second half of the 20th century. On a global level, temperatures were 0.5 degree lower.
Q: What caused this?
A: The specifics are not readily understood. But there is likely a relationship to changes in the solar magnetic field and the number of sunspots.
Q: What do you mean by changes?
A: Solar output goes through 11-year cycles defined by periods of minimum activity and maximum activity. During a period of maximum activity, the magnetic signs of the north and south poles flip simultaneously. The sun is now in the process of moving toward a period of maximum activity.
Q: Does that mean the magnetic fields will flip?
A: Yes. However, this time there are only signs of a flip in the north pole, and no indication of such a change in the south pole. It appears that the symmetry of the two poles has broken down.
Q: Is that what is causing the change?
A: Changes are also occurring in the number of sunspots. While sunspots should be occurring symmetrically in the northern and southern hemispheres of the sun, sunspots have appeared earlier only in the northern hemisphere.
Q: Does this suggest the sun is about to enter a period of hibernation?
A: We will have to wait more than 10 years before we can say it is in hibernation. Right now, the solar observation satellite Hinode is carrying out concentrated observations.
Q: Given concerns about global warming, does this mean Earth will become colder? Or does it mean it will become warmer?
A: A key reason for global warming is the increase in greenhouse gases since the Industrial Revolution. That is a different process from falling temperatures due to reduced solar activity. It is also unclear what the effects will be when those two phenomena occur at the same time. At the very least, it is doubtful whether those two phenomena will cancel each other out.
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