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Frozen is more normal

THURSDAY OCTOBER 01, 2009

According to climate experts, if we persist in this satanic habit of burning fossil fuels, the slightest further disruption or insensitivity by man could cause a catastrophe. But is life on earth really that finely balanced?

 

Life as we know it has existed and evolved for at least 500 million years. It began as primaeval slime and evolved to present day, during which time almost every calamity did happen. Yet life is still here.

 

In Precambrian time, 4.5 to 5.5 billion years ago, the Earth was born. To get an idea of this time scale, stand with your arms held out to each side and let the extent of Earth's history be represented by the distance from the tips of your fingers on your left hand to the tips of the fingers on your right. Now, if someone were to run a file across the fingernail of your right middle finger, then the time that humans have been on the earth would be erased. Another way to think of it is the last inch in two miles.

 

The Precambrian period, roughly seven-eighths of Earth's history, has witnessed the most important events in biological history. Solidification of the molten material into rocks happened as the Earth cooled. The oldest meteorites and lunar rocks are about 4.5 billion years old, but the oldest Earth rocks currently known are 3.8 billion years old. Sometime during the first 800 million or so years of its history, the surface of the Earth changed from liquid to solid. Once solid rock formed on the Earth, its geological history began. This most likely happened prior to 3.8 billion years, but hard evidence for this is lacking. Erosion and plate tectonics has probably destroyed all of the solid rocks that were older than 3.8 billion years.

 

Life arose as the first tectonic plates began to move. Eukaryotic cells evolved as the atmosphere became enriched in oxygen - and just before the end of the Precambrian, complex multicellular organisms evolved, including the first animals. But nearly 4 billion years had to pass after the Earth's inception before the first animals left their traces, roughly seven-eighths of Earth's history.

The Archaean is the name given to the period of 3.8-2.5 billion years ago. It was early in the Archaean that we think life first appeared on Earth. Our oldest fossils date to roughly 3.5 billion years ago, and consist of bacteria microfossils. All life during the more than one billion years of the Archaean was bacterial. Yet the early stages of life seems to have survived through everything that was thrown at them. The Earth's crust was ripped apart by huge earthquakes and volcanoes that make Mt St Helens look like a small firecracker. Huge comets and asteroids plunged into Earth, one which probably finished off the dinosaurs, with some impacts creating enormous craters that in time formed our lakes and oceans. And as if that hasn't been enough, the Sun has flared up and cooled down with frightening regularity and our protective magnetic field has countless times collapsed exposing us to deadly cosmic rays, not to mention magnetic pole reversals.

 

The continents have also drifted around, shifting the positions of both poles, with the result that all continents in their geological past have gone through alternating regimes of desert, jungle forest, and glaciation. For example why there is oil in the Middle East is because the Sahara Desert was once the Sahara Forest. Two interglacials ago Antarctic was 5C warmer than today. 20,000 years ago the south pole was near Perth and Antarctica was still forested and had human occupation. Western Australia was then covered with snow. At this time the North Pole was not far from Chicago, an area referred to by geologists as the Illinoisian Ice Cap. The snow then reached right to Mexico. But when studying ice cores the shifting of the poles is not taken into account, which makes ice core research typical only of an isolated area of fairly rapidly changing latitude, irrelevant to any averaging for the globe. The only likely conclusion from such an exercise is that the research funding opportunity will continue to be milked.

 

Early forms of life were certainly robust enough to withstand all these massive changes. That a few polar bears have been filmed vainly looking for seals by greenie reporters vainly looking for a good story, indicates something about species desperation but not on the part of the bears.

What causes ice ages? Most people may be under the impression that the Earth is in a circular orbit around the Sun at a distance of 149 million kms. Earth does indeed orbit the Sun, but not in a circle. In fact the shape is more like a rugby football. It is called an ellipse, and the Sun is not dead centre but offset within it. At present, this orbital eccentricity is not too far from the minimum of this cycle, which lasts 100,000 years. An ice age dawns when the orbit of Earth around the Sun changes back to a near circle after being elongated. Changing the distances from Earth to Sun over this cycle changes the distance the Sun's shortwave radiation must travel to reach Earth. The Earth-Sun distance can vary by as much as 18 million km. At the maximum end of the cycle, solar variation can vary by 30% in one year, compared to 7% at present. To accommodate the 30% annual intensity of solar radiation, climate is bound to change. During the highly elongated phase, temperature contrast is very strong, especially between northern and southern hemispheres. Any ice formed at the far end of the orbit is melted off again quickly as the Earth makes a close approach to the Sun at the near end of the orbit. But as the orbit contracts to a more regular shape the temperature contrast diminishes, and favours the growth of ice ages.

 

Because of this elliptical cycle, a major part of the geological history of Earth has been that large parts of the planet have been frozen in long ice age mode. It is not generally realized that the Earth spends roughly 80% of its time in ice age and only 20% of time in brief warm spells, and therefore ice ages are really the natural state of Earth and should be given that status. In the life of the Earth the present climate pattern is not the norm. Most periods of glaciation average about 50,000 yrs, and interglacials, which we are in now, only 10,000 years. After an interglacial the Earth settles back to normal - ice age. As it is 11,000 years since the last ice age, it is 99.99% reasonable to assume that we are now heading toward the next. In about 10,000 years, all earthlings should start to feel significantly cooler.

 

Warming is a blessing and is beneficial. Warmth brings more vegetation and life. During the last Ice Age, much of what is now tropic rain forest was dry and relatively barren savanna. Any botanic map showing vegetation 15,000 years ago will demonstrate that. Earth’s humans have already lived through many glacial and interglacials. Archaeologists have recently unearthed signs of village life in Britain and Scandinavia dating back 700,000 years.

 

To conclude, contrary to popular belief, the Earth, its climate and life itself are as tough as old boots. They could not have survived all that cosmic battering if they weren't. After every disruption and catastrophe the climate has always returned to more or less its present form. It must have some sort of mechanism which can resist any tendency to change outside narrow limits. But clearly it is not as fragile and delicate as some conservationists would have us believe. If planets could laugh, they’d love the thought of humans installing ecofriendly light bulbs to avert climate change.


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