Jagged Environment
Internal clock
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Jagged EnvironmentInternal clock |
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Mass extinctions |
The climate displays a clear periodicity over the previous 750,000 years. There is a peak in global temperature, matched approximately by a maximum in the CO2 and methane concentrations, which occurs on an almost 130,000 year cycle, interceded by ice-ages; I have previously noted that both CO2 and methane concentrations follow the temperature maximum with a lag of about 900 years, so the global heating is not caused by them, but their concentrations are increased by a hotter globe, presumably by accelerated biological activity. It has been proposed that such events are linked in some unspecified manner with the periodicity of the earth’s orbit in relation to the Sun: the major cycle is of around 100,000 years with smaller effects which operate at around 20,000 years, which might coincide with the overall climate cycle. Beyond noting an apparent coincidence in various features of the orbital period and the main climate cycle, there is no clear explanation for a connection between these phenomena. There may be no such connection. The climate cycle follows the coupling of the circulation of the oceans with the atmosphere, which acts as an internal clock. It requires a steady output, over 750,000 years, of water and gases, especially CO2 and methane, from the deep Earth, and so the release of an effectively constant amount of heat at the surface. Since heating releases CO2 from surface ocean reservoirs, further atmospheric warming occurs via the greenhouse effect, but only in the lower regions. The increased CO2 prevents heat being radiated into the higher atmosphere which then cools. As the stratosphere cools, cloud formation becomes more extensive, and this provides a larger surface on which ozone can be decomposed: the increased loss of ozone over Europe has been attributed to this. The mechanism of lifting the lid then operates. The lid is due to the ozone layer, which is a hot region that prevents escape of gases from the cooler, lower regions. As the ozone concentration falls, the lid region cools, allowing CO2 to escape. Ultimately, enough CO2 has escaped to allow the lower regions and the surface to cool. The cooling causes more CO2 to be absorbed by the colder oceans, thus reducing the greenhouse effect further. The new ice-age sets in. The reduced CO2 concentration allows more heat to be radiated into the higher atmosphere, so that the stratosphere warms. This reduces cloud formation so that the ozone levels begin to be restored. The lid then warms, and more effectively keeps the gases in the lower atmosphere in. Therefore, the CO2 levels once again begin to increase. Ozone-loss and global-warming are part of the same cyclic mechanism of climate control. The idea of continual geothermal gas production/heating obviates the need to explain the climate cycle in terms of cyclic cosmological heating events. Rather, it is the CO2/O3 feedback mechanism that is cyclic. Any action by humans which raises CO2 or reduces ozone will merely move the cycle more quickly, but will not change its outcome. Copyright © 2001 Chris James Last updated 12 March, 2005 |
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