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If planets could laugh

TUESDAY MAY 22, 2012

According to climate experts and politicians, if we persist in burning fossil fuels, this insensitivity by man could cause an environmental catastrophe, only avertable we are told by paying extra taxes. But is life on earth really that finely balanced?

Life as we know it has existed for at least half a billion years, starting as primeval slime and evolving to present day, during which time every environmental calamity did happen. Yet oddly, life is still here.

Earth was born in Precambrian time, 4.5 to 5.5 billion years ago. 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.

As earth cooled in the Precambrian, molten material solidified into rocks. As the surface of earth changed from liquid to solid our geological history began. Life arose as continents began to move. Eukaryotic cells evolved as the atmosphere became enriched in oxygen followed by complex multi-cellular organisms, including the first animals. Nearly 4 billion years had to pass before the first animals left their traces, after roughly seven-eighths of earth's history.

The early stages of life seem to have survived through everything that was thrown at them. 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 other impacts creating enormous craters that in time formed our lakes and oceans. 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 and magnetic pole reversals.

Continents have drifted around as pole positions have been ever-shifting, meaning all continents have gone through regimes of desert, jungle forest, and glaciations. The Sahara Desert was once the Sahara Forest. Only 20,000 years ago the South Pole was near Perth with Antarctica still forested and with human occupation. Western Australia was then covered with snow. At this time the North Pole was not far from Chicago, the Illinoisian Ice Cap. The ice and snow then reached to Mexico.

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 reporters vainly looking for a good story, indicates something about species desperation but not on the part of the bears.

So what causes ice ages? The tilted earth orbits the sun, but not in a circle, more like a rugby football called an ellipse, with the sun not dead centre but offset within it. This cycle 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, and our tilt slightly straightens. Changing sun-distance changes the time for shortwave radiation to reach earth. During the highly elongated phase, temperature contrast is very strong, especially between northern and southern hemispheres. 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, earth spends roughly 80% of its geological history in ice age and only 20% of time in brief warm spells. Therefore being iced-up is really the natural state of earth. Periods of glaciations average 50,000 years and an interglacial which we are in now, 10,000 years. After each interglacial, earth settles back to normal - ice age. It has been 11,000 years since the last ice age, so it is reasonable to assume that we are heading toward the next. In about 8,000 years, all earthlings should start to feel about a degree cooler.

Warming is therefore a rare blessing and beneficial. Warmth brings vegetation and life. During the last Ice Age, much of what is now tropic rain forest was dry and barren savannah. Humans have lived through many glacial and interglacials. Village life in Britain and Scandinavia dates back 700,000 years, and in the Indus Valley, at least a million years. We obviously know how to adapt to environmental changes.

So contrary to popular belief, 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, showing there is a stabilising mechanism which can resist any tendency for runaway climate change.

If planets could laugh, they’d love the thought of humans installing eco-friendly light bulbs to avert climate change. Whilst there is nothing wrong with living more efficiently and breathing healthier air, it is likely the earth is not as fragile and delicate as some would have us believe.


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