The current solar cycle 24 might be a game changer in the global climate debate. It is showing early signs of reaching the solar Maximum in two short years. Solar Maximums on average occur some 5 to 6 years in to a typical 11-year cycle.
The Sun has a cycle of about 11 years from minimum to maximum and back to minimum magnetic activity. This cycle can be observed by the numbers of sunspots formed on the surface of the Sun. During a cycle, the sunspot numbers increase, flares are common and coronal mass ejections occur until the Sun’s polarity “flips”. This usually is the point at which the so-called solar maximum is reached. The activity on the Sun begins to decrease. The cycle eventually reaches a point where very few sunspots are observed. This is the completion of a cycle.
The chart below shows the magnetic fields of several previous solar cycles and the current cycle 24. The North polar field is nearing the zero on its way to swapping sides with the south polar field. Note, also, that the magnitude of cycle 24’s field is not as large as the previous cycles.
Chart Source: http//wso.stanford.edu
Cycle 24 has been a maverick. Initially the solar cycle gurus said it would perform about the same as the previous two cycles—22 and 23. However it did not seem to want to begin and when it did, it has under preformed expectations so significantly that the performance forecast has had to be lowered many times. Cycle 24 has more in common with cycles of years ago that also exhibited reduced solar activity. These cycles coincided with global cooling.
Galileo began counting sunspots in 1610. Daily counting began 1749. From 1645 to 1715, there were very few sunspots. This period is known as the Maunder Minimum. Few sunspots were visible during the period from 1790 until 1830. This period is known as the Dalton Minimum. Corresponding to the period of time that included the Maunder and the Dalton Minimums, the Earths climate was comparatively cool. The climatic period, know as the “Little Ice Age” lasted from 1450 until 1820. The chart below shows correlation between sunspots and the Minimums.
(The chart shows non-systematically collected sunspot numbers in red. Systematically collected observation spots are in blue.)
Chart courtesy of Robert A Rohde for Global Warming Art
Here is the current plot of sunspot count for cycle 24. Also note how low the forecast of peak sunspot activity is compared to the previous cycle. Click Chart for clarity.
The “predicted values” would indicate that the cycle 24 maximum will occur in 2013. After a big jump in March, the April count is heading down and so far the May sunspot count is rather low.
So, solar activity for cycle 24 is quite low compared to recent cycles. But can we be sure that cycle 24 wont become very active? No we can’t. Can we be sure that if cycle 24 is short (less than 11 years) the climate will cool off? No we can’t. What we can say is that low solar activity appears to correlate with a cooler climate.
Why would a less active Sun result in lower global temperature? The amount of radiation from the Sun to Earth does not vary much year to year. No one knows for certain if the variation is enough to raise or lower global temperatures. The Sun’s magnetic field weakens when the Sun is less active. Some theorize that this lets in cosmic rays and that these rays form low altitude clouds. Low altitude clouds do lower the Earth’s temperature. My philosophy is: Even though the exact mechanism linking the Sun and global change has not been definitely established, it is kind of like gravity–it is obvious. If cycle 24 continues on its current track, we may see more confirmation that low activity correlates with cooler weather. We will have to wait for several years to know. Stay tuned.
This is a fantastic post. Seriously i don’t think i’ve seen such a comprehensive explanation. well done
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