Glaciers and Ice

The periodic glaciations of the present Ice Age is thought occur every 100 000 years. This has been deduced from the Vostock ice core. This core, drilled out by the Soviet scientists has shown the temperature of the last 160 000 years of snow that accumulated in the Antartica. The temperature of each layer within the core, as it was laid, is inferred by using an established correlation between temperature and the ratio of two forms of hydrogen in frozen water. 

It is also interesting to note that carbon dioxide levels seem to increase as the temperatures of the region increased. Within the glacial period the Vostock core has shown there to be several interglacial periods, lasting around 10 000 years when the temperatures get slightly warmer. At this present time we could be in the middle of one of these interglacial periods.

The reason for these periodic changes could be due to one or more factors, which alone (or more likely to be a combination) could cause cooling sufficient enough to create a glaciation period or even the Ice Age itself.

Eccentric Orbit

The first factor being that the Earth’s orbit around the sun is not circular but elliptical. Because of this eccentricity, the Earth’s magnetic fields can be strengthened and indeed reduced. An increase in the earth’s magnetic field can cause cooling as the magnetic field can repel high-energy particles from the sun, thus reducing the amount of solar energy reaching the Earth and so reducing the temperature of the planet.

Tilt & Precession

The second is due to the variations in the tilt of the equatorial plane in relation to the orbital plane of the Earth due to the tilt of the Earth about its axis (of approximately 24 degrees).

The precession cycle of the Earth can certainly cause changes as it, tectonic activity and other changes due to the Continental drift could cause a change in the weather pattern. Earth is located on a limb of the Milky Way galaxy, which rotates in space, as does the Earth around the Sun (although this rotation takes several hundred million years) and this rotation could also have an effect.

A much more contentious reason for the cooling of the planet is a dilution of one put forward by experts (including palaeomagnetism expert Joe Kirschvink) to explain the first big freeze on Earth. The trigger for this ‘Snowball Earth’ may have been due to the disintegration of the super-continent Rodinia, which allowed more chemical weathering to occur. This meant more carbon dioxide was taken out of the atmosphere and so more cooling to take place. A smaller series of similar events occurring at regular intervals could be responsible for the periodic glaciations.

A combination of some or all of the factors mentioned above could have caused the Ices Ages and to a lesser extent the glacial periods that occur.

Man-made effects

New factors that may be operating to disrupt this pattern are often man-made such as the effect of the green house gases caused by the burning of fossil fuel, the use of cars along with other industrial processes which are producing carbon dioxide, nitrous oxide and water vapour and the increase in methane levels caused by modern farming methods.

These greenhouse gases are reflecting heat back to the Earth’s surface and hence warming the atmosphere. A more worrying human induced factor was the use of Chlorofluorocarbons (CFCs) that have attacked the ozone layer. Unfortunately these CFC’s (used as refrigerants) take a very long time to break down into components that are ‘safe’ for the Earth’s protective ozone layer. Whilst no longer used in developed countries, they are still used in third world and developing countries.

The ‘hole’ in the Ozone layer can be detected in the Antarctic summer (and has recently has been detected over the Arctic region). The ozone layer in the stratosphere inhibits the ultra violet rays from reaching the Earth’s surface by reacting with the UV light to produce oxygen. The reduced amount of ozone layer therefore allows more UV light to reach earth and has also contributed to global warming and an increase in skin cancers.

The modern ways of farming with a large number of ruminants (like cows) being bred for meat and milk production has caused an increase in methane gas produced. The intensive farming of rice has also increased the amount of methane, as has the ways in which rubbish is often disposed of in landfill sites. This is due to the fact that the human population in the World has hugely increased in recent times so more food and land is needed to feed and house the people.

Is it Real?

Does it actually matter if the change is man-made or not? We should be looking after our home regardless, and allowing future generations to thrive, or at least not look back on our greed and complicity. Click HERE

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Ref.:

Sarre, P & Reddish, A (Eds)(1996)Environment & Society, Lodder and Stoughton/The Open University

New Scientist article 6th November 1999 – Snowball Earth