The Next 60,000 Years / The Mini-Iceage
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It has been mentioned, in Chapter Three, that the iceaqes of the past 2¼, million years have been caused by core-explosion heat coming closer to the surface and resulting in an increase of volcanism. Volcanic emissions have an initial short-term cooling effect, due to volcanic dust particles reducing the amount of solar heat reaching the biosphere. But, in the longer-term, when most of the dust particles have returned to the surface, the sulphurous aerosol and carbon dioxide Emissions have a Greenhouse warming effect (the El Niño/La Niña regime) which results in an increase of rainfall, land-waters, and cloud-cover. The greater incidence of land-waters raises the planetary albedo ... that is, the degree of reflectivity of solar rays ... and, as a consequence, the global mean temperature is reduced. This cooling effect becomes greatly and rapidly intensified when ice-melt waters (from the northern ice-sheets) flood into the North Atlantic, reducing evaporation and triggering the onset of an iceage. Once initiated, the cooling brings greater snowfalls, with a further boost to the global albedo and even greater cold. During the third to last and second to last iceages, the global mean temperature dropped close to zero degrees Celsius and during the last iceage, which ended 10,000 years ago, the mean dropped to five degrees Celsius.
There remains the question of the cyclical upturns: what has brought each of the past glacial periods to an end? As volcanism continues to belch forth its Emissions during the glacial periods, the continuing build-up of sulphurous aerosols in the stratosphere reaches a stage where their warming effect more than counteracts the cooling effect, and this results in an upturn in the global mean temperature and the beginning of an interglacial. However, the major factor bringing the forthcoming mini-iceage to an end, will be the arrival of more core-heat at the surface ... not only by way of increased volcanism, but also by a significant increase of the global surface heat-flux (presently 60 milliwatts per square metre per second). whereas the last iceage lasted 60,000 years, the forthcoming mini-iceage is estimated to last onlylo,000 years, and its low-temperature point will drop to a relatively mild glaciation low of ten degrees Celsius. And, whereas the northern ice-sheet reached down to 40 degrees latitude at the coldest stage of the last iceage, it is projected to reach down only to 55 degrees latitude in the next and final glaciation.
The following chart shows the iceage cycles, 1,000,000 BC to 30,000 AD, in terms of global mean temperatures.
The vertical axis shows temperature and the horizontal axis shows time. The middle line represents the present global mean temperature of 14 degrees Celsius. It will be noted that the cycles have become more frequent and of lesser duration: this is due to the arrival of more and more core-heat, via increased volcanism. The most significant movement of the temperature-line is, of course, the rapid increase from 14,000 AD onwards. From 14,000 AD to 30,000 AD, the global mean temperature will increase from 14 degrees to 28 degrees Celsius. By 30,000 AD, Earth will be virtually unliveable except for polar regions and the temperature-controlled enclaves.
The mini-iceage period, from 2,100 AD to 12,000 AD, will bring crop failures and hardship to many but there will also be positive developments, including:
But when will the present so-called warming period end? About the year 2100, the global mean temperature will begin to fall quite rapidly, and the cooling period will begin in earnest. Until then, we will experience a continuation of the El Niño/La Niña regime. Things to watch for will be further melting of the northern ice-sheets, and a downward trend in the temperature of the North Atlantic surface water.
www.NormanSpencer.co.nz / The Next 60,000 Years / The Mini-Iceage