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The Actuary The magazine of the Institute & Faculty of Actuaries

Environment: Sunspots and natural disasters

The paper by JB Dow FFA on ’Early Actuarial Work in Eighteenth Century Scotland’ (Faculty of Actuaries 16th October 1972) reminded actuaries how little mankind knew about mortality and populations back in the 18th century. The paper discussed the contributions to what would become actuarial thought processes by Robert Wallace (1697-1771), Alexander Webster (1707-1784) and Colin MacLaurin (1698-1746) in the development of a widows’ fund for the Church of Scotland.

Colin was regarded as a mathematician second only to Sir Isaac Newton, whom he knew. New space-age tools to analyze nature’s risks have become available in the late 20th and early 21st Century. Without these tools actuaries could be analyzing nature’s risks with about as much relative sophistication as Wallace, Webster and MacLaurin analyzed mortality risks in the 18th Century. But to use these space-age tools actuaries also have to work within nature’s framework. This article is about the use of that framework and what it reveals. The tools and their uses should be the subjects of many future actuarial papers by actuaries who use and develop them, hopefully for purposes well beyond the measurement of risk of major volcanic, earthquake and extreme weather events.

My previous article, ’The falling apple’, indicated that the sun had entered a state known as a solar grand minimum. There is skepticism about this and what it means, particularly among some climate scientists and presumably actuaries working on carbon dioxide abatement schemes. In Vienna on February 10, 2011, there was a United Nations committee meeting on the “peaceful uses of outer space”.

The Lead Program Scientist of the Heliophysics Division of NASA gave a presentation about the risks to business of space weather super storms. In this presentation he stated: “Space has never been closer to Earth”! He was referring to the current collapse of the ionosphere caused by "the extreme solar minimum”. He went on to say “Sensors onboard the US Air Force C/NOFS satellites have recorded a record collapse of the ionosphere.

The night-time ionosphere is only 260 miles above Earth’s surface, a sharp decrease from the usual value of around 400 miles. The ionosphere is also 100 degrees cooler than expected.” The consequences of this are significant for the US Space program. For example, satellites and space junk that should no longer be orbiting the Earth are still up there, increasing the risks for new satellite launches. This NASA scientist also indicated how this current “extreme solar minimum” is characterized by the “sun’s magnetic field being in a weird state”, the Earth being greatly more “exposed to cosmic rays”, “the radiation belts being charged with killer electrons”, all “contributing to a reduction in temperatures on Earth”. But he also said that in the long term this extreme solar minimum is not a permanent solution to global warming. His frame of reference for these statements was “since the dawn of the space age”.

The framework that should be used for analyzing nature’s risks is not earth years but the solar cycle. A solar cycle is a periodic change in the amount of irradiation from the sun that is experienced on Earth. These vary in length but on average tend to be approximately 11 years in duration. The sunspot activity within each of these cycles can vary significantly between cycles. Much of the science behind the solar cycle variations is relatively unknown. During solar grand minimums the sunspot activity is severely restricted for several solar cycles and some of that activity could be unipolar or negative sunspots.

The solar cycle framework enables a better understanding of the risk of major earthquake and volcanic activity. This is because there is a strong correlation between major volcanic activity (according to cubic kilometers of ejected matter), major earthquake activity (8.0 or more on the Richter scale) and strong solar minimums or grand minimums. In the last 250 years the following major volcanic eruptions occurred during strong solar minima or grand minima: Grimvotn (Iceland) 1783/84 (14 km3), Tambora (Indonesia) 1810 (150 km3), Krakatoa 1883 (5.0 km3), Santa Maria (Guatemala) 1902 (4.8 km3), Novarupta (Alaska) 1912 (3.4 km3). The only major eruption to occur during a solar maximum was Pinatabo (Philippines) 1991 (between 6 and 16 km3).

Pinatabo’s eruption occurred immediately after Typhoon Yunya passed directly over the top of the volcano. Japanese scientists suggest this typhoon provided the same trigger as is provided by a solar minimum (i). Their paper explores how muon (sub-atomic particle) bombardment of the caldera of active volcanoes with silica rich magma causes explosive eruptions and shows how the number of muons reaching earth during solar minimums is significantly increased. Their paper explains the science behind the relatively high incidence of volcanic activity during solar minima.

A similar correlation appears for major earthquakes (defined as 8 or more on the Ritcher scale) and sunspot activity. Increased major earthquake activity also occurs during strong solar minimums and grand minimums. A scientific explanation for the increased major earthquake activity during solar minimums has been provided by some Russian scientists (ii). Basically their theory is that the reduced magnetic pressure on Earth during solar minima enables tectonic plates to move a little more freely thus more easily allowing for the releases of built up frictional forces between them.

Since sunspot activity started lessening significantly in 2004 there have been 11 major earthquakes (over size 8.0): Solomon Islands – 8.1(April 2004), Sumatra-Andaman & Indian Ocean tsunami – 9.2 (December 2004), Nias (Indonesia) – 8.6 (March 2005), Tonga – 8.0 (May 2006), Kiril Islands (Russia) twice – 8.1 (November 2006 & January 2007), Peru – 8.0 (August 2007), Sumatra – 8.5 (September 2007), Samoa – 8.1 (September 2009), Maule (Chile) – 8.8 (February 2010), Sendai (Japan) and Pacific Ocean tsunami – 9.0 (March 2011). The previous 11 major earthquakes occurred over 38 years (more than 5 times as many years).

Differences in recording equipment could be responsible for many earthquakes not being recorded before 1950. So looking at the major earthquakes that occurred in the last 60 years 72% occurred in months where sunspot activity was below the average. The incidence rate in such months was 2.7 times the incidence rate in months with above average sunspot activity. Over the whole 260 years the incidence rate in months with below average sunspot activity was 2.2 times the incidence rate in months above average. Further, in the last 60 years, major earthquakes occurred in months with less than 50% of the average sunspot activity at 3.1 times the incidence rate for months with above 50% of the average sunspot activity. The multiple was 2.2 times for the whole 260 year period.

There is also a significant link between the El-Nino and La-Nina weather patterns and sunspot activity. Data on the El Nino Southern Oscillation (ENSO) Index obtained from the National Oceanic and Atmospheric Administration (NOAA) website was mapped against sunspot activity. The ENSO data is only available since 1950 but a pattern appeared. Strong El Nino and weak La Nina events tended to occur with, or during the decade or so, after a solar cycle with strong sunspot activity. Strong La Nina and weaker El Nino events tended to occur with, or during the decade or so, after a solar cycle with weak sunspot activity. Presumably the lag effect of ENSO activity after changed sunspot activity is due to oceans very slowly absorbing or releasing the marginal heat increases and decreases caused by the changed sunspot activity.

As the sun is now in a solar grand minimum it seems likely that there will be a prolonged period of strong La Nina and weak El Nino events as the oceans gradually release the marginal heat gained during the previous long period of much stronger sunspot activity. But if there is a large explosive volcanic event during this solar grand minimum then it is also possible that the additional airborne aerosols could trigger an extended El Nino event.

Data is available from NASA on extreme ultra-violet emissions, the solar wind speed and the sun’s magnetosphere, all of which reflect the changing sunspot activity and account for the effect of negative sunspots. This data will, in the future, provide the tools to develop better frameworks for the measurement of nature’s risks.

There should be significant actuarial involvement in use of data being obtained from space. Put into nature’s own framework this information will provide actuaries with an improved understanding of many of nature’s cycles. Actuaries will also be able to develop predictive tools for a number of areas of risk management and to assist in the underlying assumptions for much of our more traditional work.


(i) "Explosive volcanic eruptions triggered by cosmic rays: Volcano as a bubble chamber"; Toshikazu Ebisuzaki, Hiroko Miyahara Ryuho Kataoka, Tatsuhiko Sato Yasuhiro Ishimine. November 2010.

(ii) "About possible influence of solar activity on seismic and volcanic activities: Long term forecast"; Khain V. E. Khalilov E. N. Moscow State University. 2008.


Brent Walker is an ex-chairman of the International Association of Consulting Actuaries and currently works as a health actuary