Climate Addendum

This discussion is described as an addendum because it is attempting to provide some additional information regarding the Climate Change Debate – see link for details. Within this debate, a discussion entitled Climate Change Mechanisms outlined some of the potential complex causes that may affect climate, as listed below.

Milankovitch Cycles, Solar Cycles & Sunspots, Plate Tectonics,  Volcanism, Earth’s Oceans, Earth’s Atmosphere,  Earth’s Albedo,  Space Weather, Cosmic Rays, Geomagnetic Reversal,  Anthropogenic CO2

Exactly how all these mechanisms interwork within a collective climate system is still considered an issue of debate, such that a later essay entitled Consensus and Climate Change questioned the acceptance of a consensus that assumes that man-made CO2 emissions are the only or primary mechanism at work. However, this consensus appears to have convinced many governments around the world that man-made CO2 emissions will lead to catastrophic climate change, such that a policy of net-zero has to be enforced irrespective of the costs. In this respect, the discussion entitled ‘A World in Transition’ considered the wider, but related issues raised in two books entitled ‘The End of the World is Just the Beginning’ by Peter Zeihan and ‘Fossil Future’ by Alex Epstein – see links for details.

So, what additional information is this addendum seeking to review?

In part, the previous links are primarily provided as background references to earlier discussions of climate change, where this addendum will now focus on an additional climate mechanism described in a 2016 paper entitled ‘Modulation of Ice Ages via Precession and Dust-Albedo Feedbacks’ by Ralph Ellis and Michael Palmer. As the link allows the interested reader to review the actual paper for themselves, the following discussions will simply try to summarise the most salient arguments.

Note: While reading the paper is recommended, many may find a YouTube video entitled ‘Ralph Ellis: Ice Ages modulated by ice-sheet albedo, not by CO2’ to be a useful introduction.

However, if new to some of the wider issues being discussed, it is possible that some initial understanding of how solar energy from the Sun drives all weather systems and how this energy fluctuates as a result of the Milankovitch cycles may prove useful. In essence, the Milankovitch cycles result in changes in the Earth's position relative to the Sun described in terms of its precession, obliquity and eccentricity, as illustrated below, where the blue-pink zones correspond to cyclic glacial and interglacial periods.

The issue as to why red-precession and black-eccentricity curves, as shown in the previous chart, are modulated in synchronization with each other will be discussed further in the section entitled Milankovitch cycles along with some additional analysis of how these cycles will have affected climate when measured over tens of thousands of years.

Note: In the context of the long-term timescales involved in the Milankovitch cycles, it is generally assumed that they are not directly part of the present-day climate debate.

However, there is evidence that the combined effects of these cycles may have triggered glaciation events in  Earth’s history, but where the Ellis-Palmer paper attempts to explain how these cycles need an additional mechanism linked to the effects of atmospheric dust on the albedo of the Earth. The chart below shows the insolation in W/m² that equates to the input solar energy received from the Sun over the last 450,000 years, where the orange circles correspond to the start of a glacial period highlighted as colder blue zone, while interglacial period are shown as warmer pink zones

In part, the insolation curve above might be interpreted as the effective superposition of all three Milankovitch cycles, i.e. eccentricity, precession and obliquity. While Milankovitch cycles are discussed further in the link, by way of an initial summary, the Earth's axis completes one full cycle of its axial precession every 21,700 years, on average, subject to a ±20% variation. The Earth also has an elliptical orbit, where its eccentricity cycle is 99,800 years, on average, subject to another approximate ±20% variation. Finally, the tilt or obliquity angle of the Earth is subject to an average 40,600 year cycle with a ±6-8%  variations. Further details, and justification, of the [±] variation will be details in a later discussion.