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David Nightingale: Global Warming Perspective

Let’s expand our view of global warming.

According to the Berkeley paleobiologist Anthony Barnosky, (the prefix ‘paleo’ simply means ‘ancient’) species have been dying out for as long as we have records [ref.2]. There have also been 5 mass extinctions on our planet, when unusually large proportions of various species came to an end. Barnosky is not the only scientist to give vent to the scary thought that the 6th mass extinction may be underway right now [ref.2, Preface p.x].

Humans, as we know, have been changing everything – the oceans, the air we breathe, the very surface of the planet, plus we have been multiplying prodigiously, especially in poor countries. But we’ve only been around for 3 million years and the earth was formed about 4,500 million years ago.

How do we know this?

All relevant disciplines – biology, cosmology, geology, anthropology, geochemistry, archaeology – point to these approximate numbers. We know, or think we know that Lucy, thought to be among our oldest ancestors, lived approximately 3 million years ago. Clearly, we didn’t harm things earlier than about 3 million years ago because we weren’t there. But life was there, and there is plenty of fossil evidence for this, from trilobites to dinosaurs. In general, there is much consensus from those science disciplines on the rough picture of earth’s history.

There’s a particular point in time that’s worth zeroing in on, namely the previous, or 5th, mass extinction, when the dinosaurs died out.

That event, 66 million years ago is thought by physicists to be when a meteorite of about 6 miles diameter slammed into the Yucatan peninsula, raising a dark blanket around the earth that may have cut off sunlight for many years, causing a massive extinction which included the dinosaurs. The rim of the asteroid’s crater was seen from above the earth in the 1980s, and a further clue was a peak in sedimentary levels of iridium in that era. Iridium is rare on earth, whereas meteorites generally have very high levels of iridium [ref1 p123].

Let’s now look at earth’s glaciations. From ice core data there have been many ice ages in earth’s history. This melting and freezing, with associated sea level changes, are not well understood, but one possible explanation is that variations in the eccentricity of earth’s orbit would have affected the intensity of sunlight at different latitudes. Another possible cause could be a slight change in the tilt of the earth’s orbital axis, but although we are still ignorant of the most likely causes, the point is that ice sheets have come and gone, many times. Only 11,000 years ago North America and Europe were under feet of ice – ice that is still receding, as we frequently see on the news. Greenland is becoming more habitable; and northern sea passages are opening, above Siberia and Canada. Our earth goes on changing, as it always has.  Indeed, just 4000 years ago the Sahara was green and verdant. Further back, 200 million years ago, the Americas and Africa were part of Pangea, and are drifting apart still, at about a cm per year.

In the 21st century people are migrating north from overheated equatorial regions, in search of food and money (i.e. jobs). Usually they are extremely poor, and have been reproducing without control. The world population climbs onwards to levels the earth cannot necessarily support. And with our cars and planes we continue pumping CO2 into the world’s atmosphere, exacerbating the whole trend. If this process goes too fast, species may not be able to adapt, and many scientists, Barkosky included, are wondering whether humanity can ultimately dodge its own extinction. 

References:

1. “Extinctions in the history of life”  by Paul D. Taylor (Ed), Cambridge University Press, Trumpington St, Cambridge, UK, (2004).

2. “Dodging Extinction; Power, Food, Money and the Future of Life on Earth”, by Anthony D. Barnosky;  University of California Press, Oakland, California, (2014).

David Nightinglale is an emeritus professor of physics at SUNY New Paltz where he taught for 31 years. His first novel, The Centauri Settlement, is produced by TheBookPatch.com .

The views expressed by commentators are solely those of the authors. They do not necessarily reflect the views of this station or its management.

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