I now include a little known but conflicting argument for (temporary at least) global cooling. Everyone knows that there have been several ice ages in our planet’s past. The earth is now on the brink of entering another ice age, according to a large and compelling body of evidence that could last for the next 100,000 years. Ice cores, ocean sediment cores, the geologic record, and studies of ancient plant and animal populations all indicate a regular cyclic pattern of Ice age glacial maximums of about 100,000 years each separated by periods of warmer climates lasting about 12,000 years. Enter now the Milankovich Cycles, which include three astronomical phenomena.
They include:
· the tilt of the earth (23.5°) (see Essay XII) which varies over a period of 41, 000 years
· the shape of the Earth’s orbit (elliptical) which changes over a 100,000 year period
· Precession of the Equinoxes (Earth’s “wobble”) which rotates the direction of the earth’s axis over a 26,000 year period.
According to this theory, these three astronomical cycles all affect the amount of solar radiation the earth receives and work together to produce the “Ice Age maximums and warm interglacials.” Now for the downside: the original proponents of the above theory, Imbue, Hays, and Schacklton wrote in a 1976 paper that it (Milankovich Cycles) must be qualified in two ways. First, they apply only to the natural component of future climate trends and not to the anthropogenic (human) effects such as those due to the burning of fossil fuels. Second, they describe only the long-term trends since they are linked to periods of 20,000 years or longer.
Carl Sagan during the 1970’s and later promoted the “anthropogenic global warming” (AGW) theory. This is based largely on the ‘hockey stick” graph presented by Al Gore in the 2008 film “An Inconvenient Truth.” The graph shows an acute spike in global temperatures beginning in the 1970’s and continuing to the present with an exception of the 2006-2007 winter. The main flaw with the AGW theory is that it focuses on the past l, 000 years while ignoring the past million years.
The British journal “Nature” in 1999 published the Vostok ice core data collected at the Vostok Station in Antarctica. The report written by Columbia University researchers includes a record of global atmosphere temperature, atmosphere CO2 levels and two greenhouse gases from 420,000 years ago to the present.
It validates the previously held idea of regular cyclic patterns of ice age maximums and warm interglacials. The data graph also shows that changes in global CO2 levels lag behind global temperature changes by about eight hundred years. That indicates that global temperatures precede or cause global CO2 changes and not the reverse. In other words, the natural cyclic increase in global temperature is causing global CO2 to rise. Global CO2 rise or fall in response to global temperatures occurs because cold water can hold more CO2 than warm water. That’s why warm carbonated beverages lose their fizz and cold ones don’t.
The earth is warming because of the normal Ice age cycle with the resulting CO2 rise. Ultimately the Milankovich cycles described above drive the over-all process, and not anthropogenic effects.
References
Pravada December 1, 2009 Earth on the Brink of an IceAge
