After a period of increased activity during the 20th century, the sun now appears to be in an extended solar minimum. Three teams of scientists presented their results on June 14, 2011 at the meeting of the American Astronomical Society’s Solar Physics division in New Mexico that all indicate an extended period of low solar activity.
The evidence “all indicates that the next solar cycle will be delayed and the sun is headed into a quiet period”, said Frank Hill, associate director of the National Solar Observatory. According to space weather scientist Bruce Tsurutani at NASA’s Jet Propulsion Laboratory, a solar minimum is defined by sunspot number and 2008 was identified as the period of solar minimum. However, the solar geomagnetic effects on Earth did not reach their minimum until 2009. It was expected that solar activity would begin to build again by this time in preparation for the next cycle and next solar maximum, but the sun remains clear of sun spots. The sun has been unusually quite for four years and scientists do not know how long the decline in solar energy may last.
Every 22 years, the sun's magnetic field switches north and south, creating an 11-year sunspot cycle. Jet streams on the sun's surface and below are early indicators of solar storm activity, and the jet streams have not formed yet for the 2020 cycle. According to Dr. Hill that indicates that there will be little or delayed activity in that cycle. The length of the delay is not known. In recorded history there have been three episodes where the regular 11-year solar cycle has not occurred and these correlated to cool periods on Earth 1650, 1770, and 1850.
Now solar physicists warn of possible global cooling, if solar activity falls. No sunspots were visible for a 70-year period starting in 1645, known as the Maunder Minimum. The Little Ice Age, a period of global cooling, occurred along with the Maunder Minimum after the Medieval Climate Optimum, a global warming period. Several causes have been proposed for the Little Ice Age: an extended period of low solar activity, heightened volcanic activity, changes in the circulation patterns of the oceans, an inherent variability in global climate, or decreases in the human population. The earth is such a complicated system with so many inputs and dependent cycles that an accurate model has not been developed and is unlikely to be developed to test these theories.
Climate scientists on the other hand believe that an extended solar minimum will have imperceptible impact on their global warming forecasts. Nigel Calder co-author of “The Chilling Stars, A new theory of climate change” is a believer in the Solar Irradiance theory and feels that the effects of greenhouse gases are likely to be a good deal less than advertised based on a different theory of climate change. Mr. Calder believes that climate is dependent on solar radiation and that climate models do not account for solar impact.
The best measurements of global air temperatures come from our weather satellites, and they reportedly show fluctuations, but no overall change in air temperature since 1999. (Though record warm and cold years have been recorded since that time the average seems to be the same.) The leveling off of global warming as measured by air temperature while CO2 levels continue to increase is heralded by the school of thought, which says that the sun drives climate changes more emphatically than greenhouse gases do.
Solar cosmic rays intensity and frequency affect the production rate of radiocarbon, C14. This is the substance that is used by archaeologists to date objects. The original C14 content is due to the amount present in the air at the time of death or encapsulation. The atoms gradually decay back to nitrogen and thus provide a method for dating materials. It was discovered in 1958 by Hessel de Vries of Gronigen that the rate of C14 production varies. The C14 variations allowed the variation in the solar production of cosmic rays to be measured. Roger Bray of the New Zealand Department of Scientific and Industrial Research then Jack Eddy of High Altitude Observatory in Colorado documented the correlation of solar cosmic rays and the earth’s climate changes.
There is more than one theory of climate change and I certainly do not know the true importance of the factors that can impact global temperature change, but I am unwilling to dismiss any theory or area of investigation at this stage. The world is not black and white and our knowledge of the interlacing systems that make up the ecosystems of the earth is truly limited. The real world is the one that is subtly interconnected where we have limited knowledge and understanding. If this extended solar minimum occurs it will likely be possible to determine the impact of solar radiation and sun spots on climate and global temperatures.