Global Warming and Ice Ages

   The earth’s climate naturally fluctuates according to several factors including the nature of the sun and weather conditions. Additionally, the temperature of large parts of Europe and North America is dependent upon the Gulf Stream to prevent the onset of an Ice Age (Source 3). Originating in the Gulf of Mexico, the Gulf Stream taps the warm water flow of the Great Ocean Conveyor Belt, (a worldwide current) and carries the warm water and accompanying winds past northeastern America and Europe. Without this movement of water, these regions would be uninhabitable .

   However, global warming has begun to melt the Arctic Ice. Accordingly, large amounts of nearly freezing fresh water is being flushed down into the northern Atlantic and disrupting the Gulf Stream. The fear becomes that if enough of the water flows into the Gulf Stream, it could shut down. Within about 1 to 3 years, major impacts on the Northern Hemisphere’s temperatures would ensue. Results could range anywhere from a little Ice Age causing colder winter, droughts, crop failures, and desertification, to a full Ice Age. Consequently, when summers ended in the north, there would be no rain around the equator causing not only Ice in the north but drought, wind, and firestorms in warmer climates. The resulting glacial period could last anywhere from 700 to 100 thousand years (Source 7).

Evidence and Potential Causes of Ice Ages

  The theory of Ice Ages was first proposed after the discovery of evidence of glaciers (rocks, sand) in areas that do not traditionally have these elements. This “till” was caught up in the motion of the glacier and left behind at a different location (Source 1). Additionally, glacial movement left behind polished and striated bedrock pavement, altered landscapes, and carved rock (Sources 2 and 6).

  There is one large question that scientists cannot establish a definite answer to; how do Ice Ages come about? The theories break down into two major categories Terrestrial and Extraterrestrial.

  The first of the terrestrial theories relates to the presence of mountains and low sea levels. The natural process of uplifting continental blocks creating height fluctuations on the earth’s surface has some affect on the climate through alterations in wind and water patterns. (Source 2 and 4). Additionally, the opening and closing of gateways for ocean currents has the potential to isolate polar regions resulting in rapid growth of ice sheets and temperature inconstancies on the earth. Each of these is a result of plate tectonics either pushing together or pulling apart. A second theory is volcanic ash and dust could reflect the sunlight out of the earth’s atmosphere resulting in a cooler climate (Source 2). The third terrestrial theory is related to carbon dioxide. Plate tectonics have the potential to reduce atmospheric carbon dioxide virtually reversing the greenhouse effect (Source 4).

  The first extraterrestrial theory is that variations in the moon and the sun can periodically change the earth’s orbit, isolating portions enough to cause glacial formation. This theory was later altered to be what is the most likely cause (Source 2). It proposed that the sun varies according to three factors. The first is that the earth spins on its axis un-evenly up to 23.5 degrees to either side. This results in a variation of season strength. Secondly, this wobble takes 41,000 years to make a full rotation (left to right then back to the middle) providing a lot of time where one hemisphere is further away from the sun that the other (Source 5). Finally, there is a change in the earth’s orbit every 100,000 years to a more elliptical pattern moving it further away from the sun for up to 23,000 years. The final extraterrestrial theory relies on an ice dump from outer space (Source 2). Evidence comes from the fact that all major Ice Ages have occurred when these three inconsistencies occur at the same time (Source 5).

Picture courtesy of Source 4 NOVA.

History of Ice Ages

  As stated before, there are four definite Ice Ages in the history of the world; however, there is the potential that one more may have existed. The potential Ice Age would have started 1.7 to 2.3 billion years ago during the Precambrian Era. Due to the large amount of time that has passed since then it is hard to provide undisputed physical evidence of its existence (Source 2).

  While nothing is definite, the four commonly accepted Ice Ages occurred during the Proterozoic Era, Ordovician Period, Permian Glaciation (Pennsylvanian), and Pleistocene Glaciation (Quaternary period) (Source 1).

  Proterozoic Era- This Ice Age occurred from 800 to 600 million years ago. During this time it is believed that the earth was covered completely in ice that could be up to one kilometer thick.

  Ordovician Period- This Ice Age lasted from 460 to 430 million years ago. Evidence shows that during that time, the continents were in extremely different locations, placing the South Pole near present day Africa.

  Permian Glaciation Pennsylvanian)- This glaciation (Glacial period of an Ice Age) lasted from 350 to 250 million years ago. It occurred over the southern portion of Pangaea called Gonwandaland, which includes present day Australia, New Zealand, Antarctica, South America, Africa, Arabia, and India.

  Pleistocene Glaciation ( Quaternary period)- This started around 3 million years ago and ended around 20,000 years ago. An ice sheet that started in Antarctica and spread through Europe and North America ultimately covering around half the planet, characterized this particular Ice Age.

  When combined, the total time in the history of the earth spent in a Glacial Period of an Ice Age is 50 to 200 million years, only about one to four percent of the world's history (Source 2).

  While the causes of Ice Ages are disputed, one thing that is known is how they progress. When the summers are not warm enough to melt all of the snow from the winter, it builds up over centuries and forms sheets of ice. The weight of the ice eventually throws off the earth's orbit. This orbital change creates seasonal extremes at both poles, which take millions of years to re-align (Source 5). The remnants of Ice Ages however, can last much longer. In fact, some snow and ice from the last ice age ending over 20,000 years ago can still be found today (Source 6).

What is an Ice Age?

  An Ice Age is a time where the entire earth’s climate is notably colder than the traditional temperatures. Additionally, there are large temperature differences between the poles and equator with continental sized glaciers covering enormous surface areas of the globe. They traditionally occur at 200 million year intervals and last for millions or tens of millions of years. In general, an Ice Age makes the globe inhabitable due to extreme weather conditions and lack of fresh water (Source 4). The glaciers that form during Ice Ages, proceed to move from areas of high elevation to those lower due to gravity. This process can alter rivers, destroy habitats, and deposit large amounts of glacial debris (Source 2).

  There are two types of periods within an Ice Age; Glacial and Interglacial periods. When temperature drops and glaciers begin to form or grow a Glacial period is occurring. However, when the glaciers begin to recede or melt away the Interglacial period is occurring. We are currently in an Interglacial period that began 10,000 years ago. Scientists currently have evidence of four Ice Age occurrences (Source 1).

Annotated Resources

The following is an annotated list of the resources I used to compile this website. Links can be found under Resource List in the upper right-hand corner of my blog.

1)Paleontology & The Ice Age- I also found this article through EBSCO's Science Reference Center. It gives a general overview of what makes an Ice Age as well as defines the four specific Ice Ages of the past.

2)Encyclopedia of World Environmental History- I found this source through EBSCO’s Science Reference Center. It gives a general overview of Ice Ages as well as evidence of their existence and theories about what causes them in the past and future.

3)Science Daily - This website is a branch of Science Daily devoted completely to information pertaining to Ice Ages. It offers information on the latest findings through articles on new discoveries and recent research.

4)NOVA- Ice- This is the official website of the PBS program NOVA, and its episode on Ice and Ace Ages. It also offers a history of the past Ice Ages as well as hypotheses on how they came to be.

5)Ice Age Paleoecology- This website is compiled though the University of Colorado Boulder and their Ecological Research Institute. The website offers information on their findings as well as area specific information about past Ice Ages. This particular sub-page offers specific information on Ice Age Paleoecology.

6)U.S. Department of the Interior - This is the official U.S. Department of the Interior / U.S. Geological Survey website pertaining to the Great Ice Age. It provides general information on historic Ice Ages as well as the impact they had on the world.

7)Global Warming and Ice Ages- This article connects the ongoing global warming to Ice Ages by providing specific information on how increased temperatures could ultimately result in a future Ice Age.