It's nice to see a rotation of sorts in the news business. It wasn't too long ago that you could count on Pravda for your daily dose of Politburo nonsense, now that niche is being nicely filled by the New York Times. It looks like Pravda is going legit. This article is talking about the Milankovich cycles, the movements of planets and their orbits. Here is a chart that establishes the reference for the article and my comments.
The start temperature for delta T was chosen at about the current temperature as a way to normalize the charting of temperature. That point is the right side where O degrees is represented at today's approximate temperature.
Earth on the Brink of an Ice AgeIce ages come and go, they started cycling during the last 5 million years. Before that it was much warmer than today. The ice age is defined as 'glaciation periods, that last about 100,000 years. The interglacial periods last about 10,000 years. The present warm period is an interglacial,called the Holocene Period, has lasted so far about 12,000 years. So it is easy to see, the next ice age is coming. Prof Bob Carter, a paleoclimatology professor, who has a four part lecture series on geologic climate where he explains it all to the laymen - Video here.
The earth is now on the brink of entering another Ice Age, according to a large and compelling body of evidence from within the field of climate science. Many sources of data which provide our knowledge base of long-term climate change indicate that the warm, twelve thousand year-long Holocene period will rather soon be coming to an end, and then the earth will return to Ice Age conditions for the next 100,000 years.
Ice cores, ocean sediment cores, the geologic record, and studies of ancient plant and animal populations all demonstrate a regular cyclic pattern of Ice Age glacial maximums which each last about 100,000 years, separated by intervening warm interglacials, each lasting about 12,000 years.
Most of the long-term climate data collected from various sources also shows a strong correlation with the three astronomical cycles which are together known as the Milankovich cycles. The three Milankovich cycles include the tilt of the earth, which varies over a 41,000 year period; the shape of the earth’s orbit, which changes over a period of 100,000 years; and the Precession of the Equinoxes, also known as the earth’s ‘wobble’, which gradually rotates the direction of the earth’s axis over a period of 26,000 years. According to the Milankovich theory of Ice Age causation, these three astronomical cycles, each of which effects the amount of solar radiation which reaches the earth, act together to produce the cycle of cold Ice Age maximums and warm interglacials.
Elements of the astronomical theory of Ice Age causation were first presented by the French mathematician Joseph Adhemar in 1842, it was developed further by the English prodigy Joseph Croll in 1875, and the theory was established in its present form by the Czech mathematician Milutin Milankovich in the 1920s and 30s. In 1976 the prestigious journal “Science” published a landmark paper by John Imbrie, James Hays, and Nicholas Shackleton entitled “Variations in the Earth's orbit: Pacemaker of the Ice Ages,” which described the correlation which the trio of scientist/authors had found between the climate data obtained from ocean sediment cores and the patterns of the astronomical Milankovich cycles. Since the late 1970s, the Milankovich theory has remained the predominant theory to account for Ice Age causation among climate scientists, and hence the Milankovich theory is always described in textbooks of climatology and in encyclopaedia articles about the Ice Ages.
In their 1976 paper Imbrie, Hays, and Shackleton wrote that their own climate forecasts, which were based on sea-sediment cores and the Milankovich cycles, "… must be qualified in two ways. First, they apply only to the natural component of future climatic trends - and not to anthropogenic effects such as those due to the burning of fossil fuels. Second, they describe only the long-term trends, because they are linked to orbital variations with periods of 20,000 years and longer. Climatic oscillations at higher frequencies are not predicted... the results indicate that the long-term trend over the next 20,000 years is towards extensive Northern Hemisphere glaciation and cooler climate."
During the 1970s the famous American astronomer Carl Sagan and other scientists began promoting the theory that ‘greenhouse gasses’ such as carbon dioxide, or CO2, produced by human industries could lead to catastrophic global warming. Since the 1970s the theory of ‘anthropogenic global warming’ (AGW) has gradually become accepted as fact by most of the academic establishment, and their acceptance of AGW has inspired a global movement to encourage governments to make pivotal changes to prevent the worsening of AGW.
The central piece of evidence that is cited in support of the AGW theory is the famous ‘hockey stick’ graph which was presented by Al Gore in his 2006 film “An Inconvenient Truth.” The ‘hockey stick’ graph shows an acute upward spike in global temperatures which began during the 1970s and continued through the winter of 2006/07. However, this warming trend was interrupted when the winter of 2007/8 delivered the deepest snow cover to the Northern Hemisphere since 1966 and the coldest temperatures since 2001. It now appears that the current Northern Hemisphere winter of 2008/09 will probably equal or surpass the winter of 2007/08 for both snow depth and cold temperatures.
The main flaw in the AGW theory is that its proponents focus on evidence from only the past one thousand years at most, while ignoring the evidence from the past million years -- evidence which is essential for a true understanding of climatology. The data from paleoclimatology provides us with an alternative and more credible explanation for the recent global temperature spike, based on the natural cycle of Ice Age maximums and interglacials.
One interesting fact is it's not known what drives the glaciation cycles, whether they existed before the Isthmus of Panama was closed off, changing the ocean circulation currents, but the main factor appears to be the sun cycles. But we simply do not have enough data to know with any degree of accuracy.
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