Past and Present Climate States of the Earth
About 3 million years ago, a most significant geological event took place - the Isthmus of Panama was completely formed. Prior to that time, there was a wide gap between the continents of North and South America. The Atlantic and Pacific Oceans had flowed freely together in the tropics through the gap separating the American continent. Three million years ago, this gap closed and ocean currents worldwide changed significantly. What now know as the Isthmus of Panama changed the world’s climate in way that was not always beneficial to life on earth.
Starting about 2.6 million years ago, the earth commenced an ice age that exists even to this day. Many scientists believe that the Isthmus of Panama was the culprit for this present ice age we live in. Oh yes, we do live in an ice age, be we are fortunate at the present, for we live in a time period between glaciations called an interglacial period. For the last million years, and for almost 900,000 of those years, the earth has experienced much colder temperatures. So cold were those temperatures that huge ice sheets formed over North America and Eurasia, each one being more than 5 million square miles in area at the height of their growth, and at their centres, they were 2 miles thick.
Those interglacial periods, like the one we currently live within, were rather short, averaging about 10,000 to 12,000 years in length. So, in the past million years, there have been about 11 of these interglacial periods, interspersed by long cold periods of glaciation lasting from 80-100,000 years.
The previous interglacial period started around 130,000 years ago, and it was much warmer than our current interglacial. This previous one peaked around 120,000 years ago and hippopotami frolicked in the Thames and Rhine Rivers of Europe. Our own interglacial period started about 11,500 years ago. How much longer do we have before the world does plunge again into another 90,000 year period of glaciation? That is what I would like to discuss in this article.
Forces Controlling These Periods
The earth’s geography has not changed too much in the last million years. The Atlantic Ocean has increased in width slightly due to the American plates drifting further west. Of course, the Isthmus of Panama is still doing its thing to the ocean currents and thus, the period of glaciation is the norm or default condition for this age we live in.
Human civilization has only arisen in the last 10,000 years. We really know nothing else except this lovely warm period we called the Holocene Epoch, which is actually just one of eleven interglacial periods that have sprung up in the last million years. Our entire history is recorded within this very short, and very warm period of time.
There are some powerful astronomical cycles that controls this ice age we live in, and these forces enable an interglacial to appear from time to time. It seems that these short warm periods come with relative regularity - every 100,000 years or so.
There are three major astronomical cycles (Milankovitch Cycles) that control the mega-climate of the earth: (1) eccentricity, (2) obliquity, and (3) precession. These are big words to describe the more commonly understood words: (1) orbit, (2) tilt, (3) wobble (where the earth’s axis points to in the Universe) - all relating to the earth as it moves through space, and around the sun.
If the earth’s orbit was completely circular, earth would remain at a constant distance of about 93 million miles from the sun at all times. Earth’s orbit is not circular for most of the time but is elliptical. What that means is that during our orbit around the sun, there is a point when we are closest to the sun, and on the opposite side we are further away from the sun. At the present time, we are only about 91.5 million miles in distance from the sun around January 2-3 each year; whereas on July 4th of each year, we are farther away at 94.5 million miles. This means that our northern hemisphere receives more solar energy in the dead of winter due to our orbit, but less solar energy from eccentricity during our summers.
Our orbit around the sun goes through a cycle of about 100,000 years. At the peak of our elliptical orbit the range of our distance from the sun increases considerably to the extent that the difference in solar energy received can be as much as 25-30%. In other words, when the earth is closer to the sun at the peak, we might be at around only 88 million miles from the sun, but at the opposite end we would be 98 million miles from the sun. This difference would cause extremes in temperatures on the earth, according to the seasons. However, such extremes are a good thing, for during the warmer times on the earth during the interglacial periods, that is how the earth warms up and melts the ice sheets, and how the earth remains warm - through the extremes. At the present time, our orbit is only giving us a 3% difference in solar energy at the extremes, which is relatively negligible. Unfortunately, our orbit is moving towards a more circular orbit and thus, less elliptical. That is not a good thing in order to maintain a warmer earth.
What gives us the different seasons at higher latitudes is the tilt of the earth. This cycle is 41,000 years in length and at its extreme, the tilt towards the sun is 24.5 degrees and the less extreme is at 22.1 degrees. At the extreme, the difference in the amount of solar energy being received at the upper latitudes of the earth is about 15% more. Therefore, when the earth leans at 24.5 degrees in the summer, the northern hemisphere receives 15% more solar energy than it does when the tilt is at 22.1 degrees. However, this would also mean that during the winter, it would receive much less at that extreme tilt. Regardless, at the higher degree tilt, this is when glaciation is eradicated during an interglacial, and this is when the earth is kept warmer to prevent glaciation from happening.
Precession has a much shorter cycle than the other two, at approximately 19 to 26 thousand years - overall average of 22 thousand years. In and of itself, the very nature of precession had no effect upon increase or decrease in solar radiation. However, when combined at its various stages in its cycle with eccentricity and obliquity, it can have a profound effect. For you see, the cycle of precession dictates when the summer or winter of a hemisphere aligns with the orbit and/or tilt.
For instance, at the start the present day interglacial about 11,500 years ago, the summer of the northern hemisphere received maximum solar energy from the tilt of the earth and from the elliptical orbit. That is why all the continental glaciers in North America and Eurasia melted so quickly. Now, 11,500 years later, the cycle is at the opposite as less solar radiation is received in the summer as we now receive in the winter.
The first principle to understand is that it is the eccentricity of the earth that controls when interglacial periods happen. This cycle is about 100,000 years long and this coincides perfectly with interglacials occurring every 100,000 years or so. When interglacial periods occur, it is always when the eccentricity cycle is very near or at its peak. Conversely, when the coldest part of a glaciation period arrives, it is always when the orbit of the earth is almost circular - in other words, when there is little difference in the distance of the earth to the sun at any points in the orbit, much like it is now.
The second principle is that when the tilt or obliquity cycle is at or near its peak, in the middle of the peak of the eccentricity cycle, this is when an interglacial period happens. This has happened 11 times in the last million years with the 11 interglacial periods corresponding. There were no exceptions, but there were a couple of interglacial periods with double peaks - these occurred within the two different eccentricity cycles that were especially strong.
The third principle is this: interglacial periods occur when there are extremes in temperatures, and NOT when the earth is more moderate in climate. In other words, when the northern hemisphere receives very hot summers, and very cold winters, that keeps glaciation away. However, when the northern hemisphere experiences warm summers and mild winters, this is when glaciation will happen, and when it does, such glaciation will continue for almost 100,000 years.
Why am I always referring to the northern hemisphere? Well, the answer is very simple - this is where the continental glaciers have been, and will be, located - over all of Canada and the northern part of the United States, and the other one over the northern part of Eurasia (mainly all of northern Europe and Siberia). The southern hemisphere does not matter for most of it is water, but it is the northern hemisphere that contains two-thirds of all the dry land on the earth. Therefore, that is where those glaciers grow. When (not “if”), glaciation happens again, this will prove to be the greatest challenge that human civilization has or ever will, face.
When Will the Next Glaciation Occur?
We are closer to another long period of glaciation than you might think. In fact, as I did a comparison as to what were the states of the astronomical cycles when the last 10 periods of glaciation commenced, I was surprised it hasn’t happened already.
We are steadily declining towards more moderation in our orbit and in the tilt of the earth. As for the precession of the earth, it is pointing us in the direction of receiving more solar radiation in the winter than the summer in the northern hemisphere, and this drives us even closer, making glaciation just around the corner.
The earth in essence, is at a point in time when the astronomical cycles that control the ice age are allowing for glaciation to occur. Glaciation has not yet happened. Why? Well, don’t be so quick to suggest that anthropogenic global warming (AGW) is staving off the glaciation. Please note that of the previous four interglacial periods, three of the four were considerably warmer than our current interglacial. It has been estimated that their global temperatures averaged between 3 to 6 degrees Celsius more than our current period. If AGW is a reality, it should be encouraged rather than fought against. Regardless, Mother Nature will always win in the end if pitted against humankind and our meagre contributions to climate change.
But why has not glaciation occurred yet if the conditions are right for it to happen? The answer to this question rests in the concept of the “trigger.”
One should think that since the mega-climate of the earth is controlled by astronomical cycles ranging from 22,000 to 100,000 years, that the move from cold to warm, or warm to cold climates would take thousands of years to accomplish. The scientific evidence does not reveal such is the case. In fact, these records reveal the exact opposite. When such changes are made, they happen rather abruptly.
For instance, when our current interglacial period commenced 11,500 years ago, the global temperature did not slowly rise over centuries. Oh no. It happened like gang busters and global temperatures rose by 12 degrees Celsius in less than a century. That makes me chuckle when global warming alarmists today called the rise by .74 degrees Celsius in the last century as being “unprecedented.” The continental ice sheets in North America and Eurasia melted rapidly and disappeared within a few hundred years making the Holocene Epoch firmly established.
Abrupt processes happen when the world changes from an interglacial state to a glacial state, as well. A trigger is pulled, or a threshold is passed, and the temperature worldwide drops; it starts to snow and the snow stays all year round in some areas. Within 20 years, the continental ice sheets grow and the packed down snow turns to ice, and their growth does not stop for centuries. Sometimes these ice sheets may recede, due to astronomical cycles such as obliquity (tilt of the earth), but after the maximum of this cycle is finished, the ice sheets grow again. Until the maximums are achieved with the eccentricity cycle, glaciation remains for tens of thousands of years.
There are many factors controlling climate. There are long powerful ones like the astronomical cycles discussed above, and there are the smaller cycles, some of which, we have even less understanding. For instance, there is the factor as to how much solar radiation the sun actually gives off. The energy that the sun gives off is not a constant. We are now aware of these smaller solar cycles, but we are unsure of their specific patterns.
What we do know is that the sun is going into a “quiet” stage right now, and may continue to do so for several more decades. During this quiet stage, less solar energy is being given out. Ever since the sun went quiet (starting in the early 2000’s), it was observed that the global warming rate stopped and global temperatures went flat. Perhaps this was just a coincidence.
Another coincidence could have been the Maunder Minimum which occurred for most of the 17th century. During this Minimum which lasted for 70 years, the sun had virtually no sunspots and this period also coincided with the coldest part of what we term, the “Little Ice Age.”
We also know that explosive volcanic eruptions that give off large quantities of sulfur, can also make the earth very cold. Sulfuric molecules are created in the upper atmosphere and block out solar radiation. In 1815, Mt. Tambora in Indonesia blew its top and this affected the world’s climate considerably for a few years afterward. The year 1816 in the northern hemisphere is known as the year without summer. The growing season was non-existent in many areas, and snow fell in July in the northern hemisphere. People suffered all over the world due to a considerable drop in global temperature, just because of this one volcano erupting.
If during a long solar minimum, there occurred one or more major volcanic eruptions, these factors combined could be a trigger starting a glaciation period. Volcanic eruptions and solar minimums occur relatively frequently. Changes in the ocean currents could also result in dramatic climate changes instigating negative feedback cycles, considerably reducing global temperatures.
At the risk of sounding like an ice age alarmist, when I was analyzing the conditions that ended the previous 10 interglacial periods over the last million years, I came across one of those “holy crap” moments. There was a short and cooler interglacial period about 780,000 years ago. When it ended, as far as the astronomical cycles were concerned, it was the exact carbon copy as our current conditions in this present interglacial - the eccentricity, obliquity, and even the precession were exactly the same as our own at this present moment.
What we do know is that when glaciation occurs, it will be an abrupt change - encompassing only a couple of decades. At this point in time we do not know how or when, but we do know that it is coming.