Opening Comments:
Before we begin our review on Climate Change, it might be worthwhile to explain why this subject even became a serious topic for review and evaluation. Over the last decade or two, there have been so many comments made about Climate Change by politicians, academia, and scientist and some did not seem to be within the realm of plausibility. That gave reason to question many of the assertions being made. Furthermore, the media seemed to lack the will to investigate many of the positions taken on Climate Change.
This, in turn, created an apprehension about the validity of the comments being made about Climate Change, as well as to even why the comments were being made. Was it a mere lack of understanding about our planet’s climate or were there other motivating reasons. In any case, it certainly seemed as if there was a bias toward the man-made cause and in turn what was happening to our planet’s Climate. I am not a scientist or an expert on our planet’s climate. However, my curiosity was peaked. Therefore, over this past year I have researched scientific studies and articles written about our planet and its never ending Climate Change in an effort to determine what to be believe. My writing on the subject became much to long for a typical blog post; therefore the content was divided into Chapters.
So with that in mind, my research on Climate Change began.
Climate Change:
Yes, we have Climate Change. Our planet has always had Climate Change. It started with the formation of our planet, continued throughout its history, it continues today, and will continue into the future, as well. To help develop at least a fundamental understanding of Climate Change, it seems prudent to begin by examining some basic information on our planet’s historical climate and its Natural Climate Change, scientifically described as Natural Variability, which occurs over several different and overlapping time periods. We will close this section with some summary comments on Natural Variability. Following this, we will address the recent phenomenon concerning “consensus view vs. scientific method.”
During the course of our analysis, the issue of CO2 and human interaction (common words for anthropogenic) with our planet will also be commented on in various sections.
While these subjects can be very complex in scientific terms, some believe they can also be described in such a way for them to be more easily understood. My objective is to achieve the latter. Before we start, lets look at two graphs to give us a time perspective as we read through the narrative
Climate Change in “Millions of Years”
Figure 1. Paleoclimatology — Wikipedia, the free encyclopedia
Paleoclimatology is the study of changes in climate taken on the scale of the entire history of earth. Paleoclimatologists employ a wide variety of techniques to deduce ancient climates.
Summer Temperatures (0 To 2000 AD)
Figure 2 Institute of Geography, Johannes Gutenberg University Mainz – Mainz Germany
The reconstruction provides a high-resolution representation of temperature patterns in the Roman and Medieval warm periods, but also shows the cold phases that occurred during the Migration Period and the later Little Ice Age.
Natural Variability:
Now that we have two graphs that provide an idea of our planet’s climate, past and present, we will proceed with our further review. Planet earth has been going through natural cycles of cooling and warming since the beginning. It has endured Cold and Hot intervals many times over in its life. Climate Change through Natural Variability can be divided into several specific timed events. Cyclical variations in the Earth’s climate occur at multiple time scales, from years to decades, from decades to centuries, and from centuries to millennia. We will endeavor to explain each, starting with the one with the longest time intervals.
Millennial Climate Cycles:
Major glacial (cold) and interglacial (warm) periods are initiated by changes in the Earth’s orbit around the Sun, called Milankovitch cycles. These cycles have occurred at different intensities on multi-millennial time scales (10,000 – 100,000 year periods). The planet’s orbits around the sun change slowly over time, influencing where solar radiation is received on the Earth’s surface during different seasons and over the years. Some have explained this change in the planet’s orbit as gradually moving from a more or less “round orbit” as it circles the sun, to more of a pronounced “elliptical orbit” and then back to a more or less “round orbit.” This change in the earth’s orbit brings it closer to the sun than it does at other times. The different orbits affect parts of the planet differently. Naturally, in “elliptical orbit” the earth’s proximity to the sun is more pronounced either way, close or far, than when the planet is in more round orbit. This change from round to elliptical and back to round orbits is a very long-term event. A note about the origin of the name “Milankovitch Cycle.” The name is in recognition of Serbian Geophysicist astronomer Milutin Milankovitch and based on his studies of the earth’s orbits around the sun and how they vary over time.
Milankovitch Cycles — Earth’s “Orbit.” Milankovitch cycles describe the collective effects of changes in the Earth’s movements on its climate over thousands of years.
Figure 3. The Milankovitch Theory states that as the Earth travels through space around the sun, cyclical variations in three elements of Earth-sun geometry combine to produce variations in the amount of solar energy that reaches Earth
Another long-term phenomenon that is associated with long term cyclical changes is the angle of the planet’s tilt. This angle changes with time and over 41 000 years it moves from 22.1 degrees to 24.5 degrees and back again. This, of course, changes the sun’s radiation impact, as to the latitude at which it strikes the planet.
Planet Earth Tilt: Earth’s axial Tilt or “Obliquity” and its relation to the rotation axis and plane of “Orbit.” Wikipedia comment
Figure 4. Planet Tilt. This is what is known axial tilt, where a planet’s vertical axis is tilted a certain degree towards the ecliptic of the object it orbits (in this case, the Sun). Such a tilt results in there being a difference in how much sunlight reaches a given point on the surface during the course of a year.
In other words, the sun’s radiation either strikes the earth at higher or lower latitude or said another way, either closer to the equator or closer to the North or South Pole, depending on time of the tilt cycle. Ok, maybe this is a bit too scientifically technical. Just think about a top and how the size of its circular spinning diameter changes and how it tilts about its axis. The top’s circle changes and the top tilts more or less.
There is one more factor, which happens about every 26,000 years and that is earth’s “Wobble” about its axis. Before we get into the “Wobble” attributes, it is interesting to point out that we really have two North Stars, for the 26,000-year “Wobble “ cycle.
Said another way, one North Star for each half of the “Wobble” cycle or one for each have 13,000 years. One is Polaris and the other is Vega, depending on where the earth is in its “Wobble.” Astronomers call the wobble of Earth’s axis precession. While most of us are familiar with our planet’s primary motions — rotation (spinning once a day) and revolution (orbiting the Sun once a year) — few are aware of precession. To see this characteristic vividly demonstrated, observe a spinning top or gyroscope. Its tilted axis of rotation gyrates in a circular motion, sweeping out a cone-shaped area in the process.
Planet Earth’s “Wobble” or Precession. Planetary Precession is due to the small angle between the gravitational forces of other planets on earth.
Figure 5. Axial Tilt or “Precession” is a gravidity-induced, slow, and continuous change in the orientation of Planet Earth rotational axis, similar to a “Wobble” of a top.
You can cause a top or gyroscope to precess by gently tapping it while it’s spinning. The “tap” that causes Earth’s axis to precess is the gravitational pull from the Sun, the Moon, and, to a much lesser extent, the planets. Gravity alone, however, won’t do the trick.
But it just so happens that Earth has a slight equatorial bulge, and it’s this bulge that gets the gravitational tug. In other words, if our planet were a perfect sphere, there would be no precession.
While a top or gyroscope might precess several times each second, a single precession of Earth’s axis takes nearly 26,000 years (25,772 years, to be exact). The effects — changes in our “pole” stars, a shift in the celestial coordinates of right ascension and declination, and a westward drift of the solstices and equinoxes — are so gradual that most changes take decades to be noticed.
So, now we have an earth “Orbit,” an earth “Tilt,” and an earth “Wobble”
Let’s put it all together before we move on from this Millennial Section. The sun’s radiation either strikes the earth at higher or lower latitudes or said another way, either closer to the equator or closer to the North or South Pole, depending on the “Orbit,” the “Tilt,” and the “Wobble”. This is the longest Natural Variability cycles of the planet. The scientific names are: “Eccentricity” or the changing orbit, “Obliquity” or the tilting about the axis, and “Precession” or the wobbling about the axis.
Ok, maybe this is a bit too scientifically technical. Just think about a top again and how the size of its circular spinning diameter changes over time (seconds and maybe minutes) and how it tilts about its axis and how the top tends to wobble when the tilt varies. The top’s circle changes, the top will tilt, and wobble about its axis.
Not at all to minimize the importance of our Earth’s Precession or “Wobble” with another comparison to a top, as there is a whole field of study into this aspect of long term climate cycles. The Precession or “Wobble” Cycle is of 25,920 years in duration. In 127 BC, The Greek astronomer and mathematician Hipparchus talked about the “Precession Cycle,” the related “Precession Equinox” and “The Great Year.” For some added clarification, the Equinox refers to one half of cycle. Some researchers contend it was known even before Hipparchus.
The implication of “Precession Equinox” is; that is when catastrophic climate events occur, such as really catastrophic, as in earth changing events. Hopefully this helps to clarify the earth’s “Orbit,” “Tilt,” and “Wobble.”
By the way, NASA defines “The Great Year” as; “The period of one complete cycle of the equinoxes around the ecliptic, about 25,800 years…
Many scientists and climatologists believe and that an understanding of the earth’s climate must start with a thorough knowledge of the Milankovitch Cycles. From this, the other aspects of climate change can add to the overall understanding. We concur with this and philosophy and hopefully the readers do as well.
Chapter 2 coming soon
Jantzen Chronicles 