Solar Activity and Global Temperatures

The media are starting to report something I have been talking about for years. It's still a bit early to say for sure, but it is looking increasingly likely that, rather than global warming we are possibly headed for something MUCH more serious as our sun changes.

This report is taken from an article written by Paul Dorian of Vencore Inc. (June 2015)

The sun's surface is currently almost completely blank. The main driver of all terrestrial weather and climate, the entity which contains 99.86% of all of the mass in our solar system, the great ball of fire in the sky which keeps us all alive has gone very quiet during what is likely to be the weakest sunspot cycle in more than a century. The sun's X-ray output has flat lined in recent days and NOAA forecasters estimate a scant 1% chance of strong flares in the next 24 hours. Not since cycle 14 peaked in February 1906 has there been a solar cycle with fewer sunspots. We are currently more than six years into Solar Cycle 24 and the current nearly blank sun may signal the end of the solar maximum phase. Solar cycle 24 began after an unusually deep solar minimum that lasted from 2007 to 2009 which included more spotless days on the sun compared to any minimum in almost a century.

Solar maximum
The smoothed sunspot number (plot below) for solar cycle 24 reached a peak of 81.9 in April 2014 and it is looking increasingly likely that this spike will be considered to be the solar maximum for this cycle. This second peak in the cycle surpassed the level of an earlier peak that reached 66.9 in February 2012. Many solar cycles are double peaked; however, this is the first one in which the second peak in sunspot number was larger than the first peak. Going back to 1755, there have been only a few solar cycles in the previous 23 that have had a lower number of sunspots during its maximum phase.

Sunspot numbers for the prior solar cycle (#23) and current solar cycle (#24) with its two peaks highlighted; courtesy Hathaway, NASA/ARC

Consequences of a weak solar cycle
First, the weak solar cycle has resulted in rather benign “space weather” in recent times with generally weaker than normal geomagnetic storms. By all Earth-based measures of geomagnetic solar activity this cycle has been extremely quiet. However, while a weak solar cycle does suggest strong solar storms will occur less often than during stronger and more active cycles, it does not rule them out entirely. In fact, the famous "superstorm" Carrington Event of 1859 occurred during a weak solar cycle (#10). In addition, there is some evidence that most large events such as strong solar flares and significant geomagnetic storms tend to occur in the declining phase of the solar cycle. In other words, there is still a chance for significant solar activity in the months and years ahead. Let's not underestimate what this might mean. The Carrington Event caused telegraph machines to catch fire due to the energy impulse received at Earth's surface. In the modern world at a minimum this could mean loss of satellite communications (telephone service and satellite TV) and loss of the GPS system (aircraft, marine and automobile navigation) as the satellite electronics for all orbiting satellites are fried by the radiation pulse. More seriously, the complex electrical power grids covering most developed countries would be overloaded and major transformers would most likely be lost. The resultant power cuts could last for months. Imagine London or New York without electricity for that long a period. We had better hope that our Sun does not "burp" as it did in 1859.

Second, it is known that solar activity has a direct impact on temperatures at very high altitudes in a part of the Earth’s atmosphere called the thermosphere. This is the biggest layer of the Earth’s atmosphere which lies directly above the mesosphere and below the exosphere. Thermospheric temperatures increase with altitude due to absorption of highly energetic solar radiation and are highly dependent on solar activity.

Finally, if history is a guide, it is safe to say that weak solar activity for a prolonged period of time can have a cooling impact on global temperatures in the troposphere which is the bottom-most layer of Earth’s atmosphere - and where we all live. There have been two notable historical periods with decades-long episodes of low solar activity. The first period is known as the “Maunder Minimum”, named after the solar astronomer Edward Maunder, and it lasted from around 1645 to 1715. The second one is referred to as the “Dalton Minimum”, named for the English meteorologist John Dalton, and it lasted from about 1790 to 1830 (below). Both of these historical periods coincided with colder-than-normal global temperatures in an era now referred to by many scientists as the “Little Ice Age”. In addition, research studies in just the past couple of decades by Swedish scientist Henrik Svensmark have found a complicated relationship between solar activity, cosmic rays, and clouds on Earth. This research suggests that in times of low solar activity where solar winds are typically weak; more cosmic rays reach the Earth’s atmosphere which, in turn, has been found to lead to an increase in certain types of clouds that can act to cool the Earth.

Outlook
The increasingly likely outcome for another historically weak solar cycle continues the recent downward trend in sunspot cycle strength which began over twenty years ago during solar cycle 22. If this trend continues for the next couple of cycles, then there would be increasing talk of another “grand minimum” for the sun, which is an extended period of low solar activity. Some solar scientists are already predicting that the next solar cycle, #25, will be even weaker than this current one. However, it is just too early for high confidence in those predictions since many solar scientists believe that the best predictor of future solar cycle strength involves activity at the sun’s poles during a solar minimum and the next solar minimum is still likely several years away.

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