Jack H. Schick

"Some Say the World Will End in Fire, Some Say in Ice" (Robert Frost)



Posted: Friday, February 03, 2012

by Jack H. Schick

Mankind has been lucky, so far. Over the past few million years the surface temperature of the planet has been much colder than it has been over most of Earth's history. However, the most recent, Pliocene-Quaternary Ice Age, has been relatively short, and, compared to previous cold spells, ice has covered only a moderate portion of the Earth's surface. For only about three million years, there have been repeated fluctuations in severity, retreats and advances of the ice sheets. We have been experiencing an interglacial (relatively) warm spell for about 12,000 years, but scientists consider us to still be in an ice age.

Unfortunately, if the Quaternary is similar to the pervious ice ages that have struck the planet, we potentially have another thirty million to another several hundred million years before the planet returns to its normal, much warmer climate. Fortunately, human activity has begun to have an effect on the environment, albeit, in the overall scheme, a minor one. It cannot be compared to orbital, solar, geographic/oceanic and volcanic influences. Man has at least achieved a level of industrialization that might enable him to be a factor in delaying the next surge of glaciation that would severely affect civilization and put stress on the survival of the species, itself.

For most of its history, the Earth has been totally ice free (the Earth is estimated to be about 4.6 billion years old). There have, however, been at least five major ice ages. Each of them had warmer, interglacial periods like the Earth is now in, but the temperatures remained lower than normal and frequently became frigid for long periods. The Huronian glaciation period is the earliest known. It began about 2.4 billion years ago and with fluctuations like all ice ages had, lasted for 300 million years. There is no way, across the vast eons of time, to determine what caused temperatures to plummet.

                                       

The second cold period, the Cryogenian Ice Age began about 850 million years ago.  It is believed to have been set off by massive volcanic eruptions that blocked out sunlight. It was the most severe of all the glaciations. It is often called the "snowball Earth" period. At times, the entire surface of the planet was covered with ice. The oceans were frozen to a depth of over a mile, except, possibly around under sea volcanoes. The Cryogenian ‘deep freeze' lasted, with a few thaws, for 220 million years.

A third, the Andean-Saharan Ice Age, was relatively short, beginning 460 million years ago and lasting a mere 30 million years. Its cause is not known, but is speculated to be associated with decreased solar activity, or again, volcanic eruptions. It was the first glaciation period to occur after complex animal life, like trilobites and fish, inhabited the Earth.

The profusion of plant life on the planet is believed to have lead to the Karoo Ice Age that began about 360 million years ago and lasted for 100 million years. In the hot, wet conditions the continents became covered with huge fern forests (this was the period in which most of our coal was created). Photosynthesis ran rampant. Carbon dioxide (a greenhouse gas), levels in the atmosphere were dramatically reduced by an increased ocean surface area and plant respiration. Atmospheric oxygen levels exceeded 35% and promoted fire storms. There are indications that huge portions of the planet's vegetation burned. The smoke blocked out sunlight and prompted the onset of an ice age.

We are now living in the Pliocene-Quaternary Ice Age. It began about 2.58 million years ago. Because it is more recent, we are able to study it more closely. This ice age has a 40,000 and a 100,000 year cycle. These cycles seem to be related to the eccentricity of the Earth's orbit (it is not a perfect circle), with variations in the planet's tilt on its axis and its precession (axis wobble). The Earth's orbit around the galaxy and solar radiation output are also important factors in the temperature fluctuations that have been seen. Changes in the location of tectonic plates, ocean currents, wind patterns and atmospheric composition as well as super-volcanoes also have an effect. For example, the closing of the Panama isthmus 3 million years ago disrupted oceanic circulation and is a probable cause of this ice age.



Over the past 740,000 years there have been eight glacial cycles. The study of seafloor sediments and Greenland ice cores show that climatic change during the past quarter million years has not been smooth but has changed frequently and abruptly. Temperatures have swung from warm to frigid in only a few decades. This has been reinforced by records accumulated over the past half a century. In the early 1970's many scientists were convinced that a new period of glaciation was imminent and called for immediate remedial action. No action was taken and, three decades later, many scientists are now convinced that the warm spell will continue.

Temperature and climatic fluctuations are common, during the Quaternary Ice Age, but the Holocene interglacial period is unique. Previous warmer intervals were interrupted by numerous frigid spells that lasted for hundreds or thousands of years. The stability of the current warm spell (excepting, among others, the 8.2 Kiloyear Event and the Little Ice Age), has made it possible for humans to flourish; to develop agriculture, civilization and ultimately to industrialize to a point that there is hope that they can have an effect on the dramatic climate swings the planet has experienced for eons.

Though previous interglacial periods have averaged about 10,000 years (this one began 12,000 years ago), some climatologists predict that the current, Holocene period could last up to another 50,000--if the CO2 concentration in the atmosphere increases to 750 parts per million. The atmospheric CO2 level is currently about 385 p.p.m., but is rising rapidly, due, in part, to human activity. However, even at current levels, there has been no appreciable increase in global temperature over the past 15 years. The advantage of increased atmospheric CO2 is being offset by other natural factors, particularly diminished solar activity. If the CO2 concentration drops to 210 parts per million, predictions are that the next surge of glaciation is probably imminent. Regardless, myopia has developed and there are concerted efforts by some groups to halt the CO2 increases.

                                

The most recent glaciation cycle of the current ice age began to end about 15,000 years ago, but there have been several sever resurgences during the Holocene period. The Younger Dryas period, named after an indicator genus, the alpine/tundra wildflower Dryas octopetala, occurred between 12,800 and 11,500 before present (b.p.), and was one of the most severe. Indications are that the temperatures in Greenland dropped up to 27 degrees Fahrenheit in about a decade.

There are several theories as to the cause of this abrupt, dramatic climate change. One suggests it was the result of the collapse of the North American ice sheets and the emptying of fresh water Lake Agassiz into the North Atlantic Ocean.  This disrupted the transfer of tropical warmth north by the Gulf Stream and the North Atlantic Drift currents. Another theory speculates that, due to the topographical change as the ice ‘mountains' melted, the jet stream shifted north, bringing more precipitation to the higher latitudes.  Again, large quantities of fresh water pouring into the arctic seas disrupted the thermohaline circulation (heat transferring by worldwide major oceanic currents). An ice free ocean also tends to absorb carbon dioxide from the atmosphere more efficiently, promoting global cooling. Another theory suggests there was an impact event, though there is little evidence of it.

During the 1,300 year Young Dryas, glaciers re-grew and, in Europe, extended as far south as the Mediterranean. The cold, dry conditions in Africa, Asia and the western hemisphere dramatically reduced food sources. Many anthropologists believe this climate change is what forced fledgling human groups in the Middle East and other populated areas to abandon their hunting and gathering lifestyles and develop agriculture.

Another cooling period began about 8,200 years b.p. (frequently refered to as the 8.2 kiloyear event). Most scientists agree that this abrupt climate change was the result of Lakes Agassiz and Lake Ojibway breaking through the retreating Laurentide ice sheet in North America and dumping millions of cubic miles of fresh water into the Atlantic. The ice resurgence was much less than in the Dryas period, temperatures dropping only about 11 degrees F. It was of much shorter duration as well, lasting only about 150 years. Anthropologists suspect that the droughts that accompanied this cold spell drove populations in Mesopotamia toward irrigation and organized settlements which lead to the first human civilizations.

                                      

There is no reason to believe that the Quaternary Ice Age will soon be over. It has lasted only one tenth as long as the shortest previous ice age. There is no reason to believe that the Holocene warm spell in which we are now living will be any longer or warmer than pervious interglacial periods. Rapid and severe climate changes are the norm during ice ages. There are several conditions that have caused a resurgence of ice sheets during the Quaternary that are accumulating at the present time.

Solar Activity: One of the most sever cooling events in recorded history occurred between 1600 and 1800 a.d. It is called the Little Ice Age. During this period sunspot activity was at an historic minimum. It is called the Maunder Minimum and is blamed, in part, for the cold spell. Today we should be at the peak of sunspot activity in the repetitive 11 year cycles, but the activity is mysteriously absent. Scientists say that we will duplicate the Maunder Minimum for the foreseeable future.

                               

                                 There are predicted to be very few sunspots in 2012

                                       

                                             Little Ice Age during Maunder Minimum

Reduced Arctic Ice Cover: Though it seems illogical, an ice-free Arctic Ocean can prompt a glacial resurgence. When ice covers the sea there is little evaporation and Polar Regions are as dry as deserts. An ice-free ocean absorbs solar radiation during long summer days and evaporates huge amounts of moisture into the Arctic atmosphere. The increased snow fall enables glaciers to form at lower latitudes reducing the over all temperature of the Earth. Open seas also efficiently absorb carbon dioxide, a greenhouse, and planet warming gas. Over the past decade there has been a dramatic decrease in Arctic Sea ice cover, and, as should be expected, dramatically increased precipitation in Canada and Siberia. Fresh water freezes at a higher temperature than salt water. In October of 2011 the speed at which ice formed in the arctic region also set a record. The increase snow and ice cover reflects more solar radiation exacerbating the cooling trend.

Fresh Water Flowing into the Sea: At least twice during the Holocene interglacial period Lake Agassiz that formed in central Canada as a result of melting ice sheets, burst through barriers and surged into the oceans. It is believed to have caused the Younger Dryas cooling by dumping hundreds of thousands of cubic miles of fresh water into the Arctic Sea, forcing polar waters south into lower latitudes and disrupting ocean currents for years. It is also believed to have surged out through the Great Lakes and St. Lawrence valley causing the 8.2 kiloyear event. This event is speculated to be the source of the worldwide flood myths. Today, due to increased precipitation in the higher latitudes and the circum-polar winds, a huge dome of fresh water has accumulated in the Arctic Sea. The sea level in a large area has bulged 6" higher (according to satellite studies). A shift in wind direction (which did occurred in 2005), will allow the water to surge out into the lower latitudes disrupting currents and having a general cooling effect on the whole planet.

                            

                                                            Lake Agassiz 10,000 b.c.

Hopefully, human activity can have an effect on Earth's climate. Prior to the Industrial Revolution, carbon dioxide levels in the atmosphere had reached low levels that, in the past, had precipitated glaciations. But they are now increasing rapidly. The current 385 parts per million concentration is no where near the 700+ ppm geologists and some climatologists claim would extend this interglacial period for up to 50,000 years. Humans can have no effect on solar activity, oceanic currents, orbital cycles or volcanic eruptions.

We must face the fact that we are living in an ice age and must endure temperatures that are well below the average of Earth's history. We must face the fact that there will be substantial climactic changes caused by things we cannot control or fully understand. From careful documentation over several hundred years, from aerial observations and studies by sophisticated instruments for only a few decades, we can draw no valid conclusions about the behavior of the climate of a planet that has been changing and evolving for over 4,600 million years.

                                         The near or far future?
                             
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Top-level comments on this article: (1 total)
» left by elle kynzer 106 days 21 hours ago.
32 fans. Follow elle kynzer on twitter!
Rev 21:1 All good and bad things must come to an end...but it's not clear exactly how...only that it passes away. The fact that "an Angel is standing in the Sun" (NIV)...hmmm
» left by Jack H. Schick 103 days 20 hours ago.
99 fans.
not sure what you mean
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