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The Actuary The magazine of the Institute & Faculty of Actuaries

Climate change: The falling apple

Why write an article about a falling apple? The apple watched by Sir Isaac Newton when it fell in 1666 led to the theory of universal gravitation — but the learning process has not ended. Now armed with modern satellites, powerful telescopes and extensive computing power, solar physicists are learning how gravitational interactions between the sun and the planets affects climate.

Over the next 20 years, Sir Isaac reasoned that the sun would not be stationary but would move in orbit around the centre of gravity of the solar system, but as the movement of the planets is not uniform the centre of gravity of the solar system is in motion. Astronomers today use this principle to search for planets orbiting far off stars.

A simple demonstration of the fundamental principle of gravity occurs every day with tidal flows. Around the solstices, when the sun and moon are aligned, their combined gravitational forces create higher than normal tides. Other planets will also at times have an effect on tides, but their influences are too weak to be noticed.

The exact position of the planets at any point in time is important to space exploration. In the 1970s the Jet Propulsion Laboratory (California Institute of Technology) produced the first ephemeris, a computerised map providing the exact location of the sun and planets at any moment in the recent past, present and future. This is continually refined and updated. Studies of the ephemeris have indicated that in the past specific conjunctions of planets have heralded similar climatic changes.

The sun is a gaseous body comprised primarily of hydrogen (71%) and helium (27.1%) and it comprises more than 99.86% of the mass of the solar system. The sun’s tremendous gravitational forces cause most of it to be in the form of plasma, which is subject to magnetic and gravitational influences. It has a thermo-nuclear core generating energy at the equivalent of 700,000 hydrogen bombs per second. Although extremely hot at the core, the surface is only around 5,500deg C. (Its diameter is 1,391,000 kilometres). The sun revolves at up to 34 days near the poles and around 25 days at the equator, although its radioactive core does appear to spin evenly. The differences in spin, together with solar storms and sunspots create turbulent magnetic forces that extend to well beyond Pluto.

Since 1755, sunspot activity has been routinely measured and solar cycles determined. More recently, we have also started to measure other outputs from the sun, which include extreme ultraviolet light, various types of radiation, solar wind, (mainly electrons, protons and helium atoms), and so on.

A lot of new data about the sun is currently being obtained from the Solar Dynamics Observatory satellite, which was launched by NASA in February 2010. This information helps to determine how the sun behaves and how it influences Earth’s climate.

Past estimates of the sun’s activity have been obtained from measurements of Carbon 14 and Beryllium 10 (14C and 10Be) in such things as ice cores, plants and rocks. 14C and 10Be are produced in the atmosphere from the interaction of nitrogen and oxygen with neutrons produced by cosmic rays. The sun’s magnetic field and the solar wind normally shield Earth from most cosmic rays, therefore higher levels of 14C and 10Be are generated when the sun’s solar wind is reduced. The half-life properties of 14C enable radiocarbon dating and results of measurements of 14C and 10Be from ice cores, rocks, and so on, indicate that the sun’s activity has changed after specific conjunctions of planets.

The current, extremely quiet, solar cycle 24 has solar scientists very interested as they are witnessing events that will significantly expand scientific knowledge as to what happens to the sun after a recent planetary conjunction similar to one that occurred in the late 1780s. These scientists believe that the Earth’s climate is entering a new cool period similar to the one that occurred from 1790 to 1830, the Dalton Minimum. The past two cold winters in the Northern Hemisphere and the extreme winter of 2010/11 are indicative of this theory.

Solar cycle 24 began on January 10 2008 after a relatively weak ending to solar cycle 23. Solar cycle 24 has continued to be very weak indeed, adjusted for changes in technology and recording equipment it shows less sunspot activity than solar cycle 5, which commenced in May 1798 and ended in December 1810. Observers are also noticing that many sunspots are unipolar spots that can act as negative sunspots, further reducing extreme ultraviolet emissions, the solar wind and hence reducing the magnetosphere. At this stage in the solar cycle, the extreme ultraviolet output of the sun is at least 15% below normal and the solar wind is 40% to 50% slower than normal. This means less northern and southern auroras and more 14C and 10Be created in Earth’s upper atmosphere.

There are many theories as to what causes the sun to go into quieter periods and what kick-starts higher activity — as in the last three decades of the 20th Century. There is no doubt that planetary gravitational fields affect the sun and its magnetic fields, but how does this happen? Just as the angular momentum of the moon and the sun in conjunction cause king tides on Earth, the angular momentum of great planets — Jupiter, Saturn, Uranus and Neptune — cause changes in the sun’s plasma, particularly when in certain configurations. Solar scientists have taken this theory to a new level by including the angular momentum of the dwarf planets and large asteroids and including amplifying spin orbit coupling forces in their calculations. They have also performed similar calculations at other times of previously occurring similar planetary configurations.

Over the last three years there have been significant changes occurring in Earth’s upper atmosphere. The thermosphere (90-600km above Earth’s surface) is affected and this part of the atmosphere helps to determine the strength and direction of jet streams, particularly the polar jet streams. For example, the jet stream over Russia and down through Pakistan stayed stationary for so long in the northern summer of 2010, that enormous floods occurred in Pakistan and forest fires in Russia. Low solar outputs directly cool the ozone layer and hence create additional turbulence in the upper atmosphere leading to more common La NiÑa and extreme weather events such as hurricanes, thunder-snow and blizzards. La NiÑa weather patterns also predominated during previous Grand Minima.

Around the time of the Dalton Grand Minimum, England started colonising Australia. Early records suggest Eastern Australia was warmer and wetter for the first 50-60 years of settlement even though the Northern Hemisphere was colder. For example, in 1788 the Thames was frozen for seven weeks, yet in Sydney a maximum of over 100 degrees Fahrenheit was recorded by Watkin Tench, the captain of the Marines, on at least one day each week in the summers of 1788/89 and 1789/90. The last Frost Fair was held on the Thames in 1814 but a short El NiÑo event caused a drought in New South Wales that year. This new Grand Minimum could produce similar climatic conditions.

As the new Grand Minimum progresses, the defining issues — at least for the working life of today’s actuaries — will be population density, food and energy security. There will be strong inflationary forces due to scarcity of food and energy, because of mankind’s unpreparedness for this climate change. There are significant implications for actuaries. In particular, the general insurance industry must use appropriate climate models that are calibrated to planetary effects on the sun, using ephemeris data and solar physics research. Otherwise, the industry will become financially compromised during this solar Grand Minimum. Apples fall today just as they did in 1666...


I am indebted to Geoff Sharp who peer-reviewed this article for me. A recent publication of his provides a reference point to many other important scientific works in this area. The paper is ‘Are Uranus and Neptune responsible for Solar Grand Minima and Solar Cycle Modulation?’ and it is published in the Cornell University Library.


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