Saturday, April 21, 2007

Gaia and Global Warming

Life originated in an atmosphere of ninety-five per cent carbon dioxide. We know carbon dioxide as the gas that we breathe out and that forms the bulk of a car's exhaust. Four billion years ago or four eons ago it was volcanoes, not cars that were belching it out. The air would have been poisonous to humans and any other animal life. You wouldn't think that such an atmosphere would be conducive to life and yet it was. The sun was younger four eons ago and it was a lot cooler – twenty-five per cent cooler than it is today. If it wasn't for the atmosphere of carbon dioxide the Earth would have been a ball of ice, just like the outer planets. But the carbon dioxide magnified the heat from the sun because it is a greenhouse gas. It is transparent to the sun's light rays, letting them pass directly through to the Earth but reflecting back the infrared heat rays that emanate from the Earth.

Carbon dioxide is what kept Earth at just the right temperature given the weakness of the sun relative to today. And the conditions of the sea were just right for life to develop at .9 % salinity. Today the sea is 3.5 % salt. The conditions were just right. What is it about life? Life is bound by certain constraints and living cells perish when conditions are not right.

So how did life survive in the face of changing conditions if it needed the conditions to stay the same? Just as the environment changed life, life began to change the environment, affecting the salinity of the oceans, changing the content of the atmosphere, and altering the climate. And it wasn't by conscious purpose, it was more a consequence of certain properties of life.

James Lovelock, a British scientist, tells us how these environmental constraints work:

.... They depend upon the tolerances of the organisms themselves. All life forms have a lower, an upper, and an optimum temperature for growth and the same is true for acidity, salinity, and the abundance of oxygen in the air and water. Consequently organisms have to live within the bounds of these properties of the environment.

Notice Lovelock talks about the optimum amount of oxygen – and yet I've been telling you that there was no oxygen in the atmosphere when life was born. Now there is 21% oxygen in the air. If there wasn't we'd be having trouble breathing because all animals and insects need at least 15% oxygen in order to make their muscles move. At the same time if the air had 25% oxygen, even wet vegetation would burn and all the forests on Earth would go up in flames in a matter of months. At the time that life came into being there was only trace amounts of oxygen in the air. Oxygen is a very reactive element. It's what gives many red things their colour, like red rocks, the surface of Mars, and blood. Oxygen in the atmosphere is also what gives the sky its blue colour.

The very first life was a cell. A bacterial cell we call “Archaebacteria” . Its closest relatives are still living today – but they survive only in places where there is very little oxygen. In muds and in the guts of herbivores like cows. All living cells are related to Archaebacteria because it was the first cell.

Life is four billion years old. That's old. And during those four billion years – that's one quarter the age of the universe – the Earth's environment has always supported life, even though the heat of the Sun has increased by 25% during that time. Eventually the Sun will grow too hot for life to exist on Earth and life will perish. We've only got about one billion years left. Better make your wills now. But it could be a lot sooner if we manage to raise the proportion of greenhouse gases high enough.

Remember James Lovelock's saying that life needs to live within environmental constraints. I call this the “goldilocks property of life” because life prefers to live in just the right conditions like baby bear's porridge - “not too hot and not too cold”; not too salty, not too watery, etc. Lovelock lists three other significant properties of life.

The second property is that if the right environmental conditions open up a living organism will grow vigorously until it has occupied its entire niche. I call this the “kudzu property” after the aggressive green leafy vine that inundates vacant lots and fields in the American South.

When life first existed, the conditions must have been just right – ocean salinity was in the right range because of the ocean's relative youth, and the temperature of the Earth was in the right range. So archaebacteria was able to thrive and fill its entire niche – which happened to be the entire global ocean four eons ago.

But archaebacteria didn't just fill its entire niche. It started changing, generation after generation. And some of those changes survived and new types of bacteria developed. This brings us to Lovelock's third property: All life undergoes Darwinian natural selection – organisms with the most progeny survive. We often understand Darwin's theory of evolution to mean: When the environment changes, organisms that can adapt to those changes survive and those that don't become extinct. The problem is if the environmental changes become too extreme then no life can survive.

Three and a half eons ago a bacteria called cyanobacteria came into existence. The big difference between cyanobacteria and archaebacteria is that cyanobacteria can photosynthesize. It can take carbon-dioxide out of the air and by using energy derived from the sun, split the molecule into carbon and oxygen, keep the carbon atom for its own use while liberating two atoms of oxygen into the air. And that's what cyanobacteria did two billion years until the amount of Oxygen had built up to its present concentration of 21%. At the same time it was producing all this oxygen it was sequestering carbon and so the amount of carbon dioxide diminished.

That leads us to Lovelock's fourth significant property of life: All organisms change their physical and chemical environment. The easiest way to understand this is to think about breathing: we change the air every time we breathe by taking in oxygen and breathing out carbon dioxide. If we are in an enclosed space and there is no air circulation then the air would quickly become too high in carbon dioxide and too low in oxygen and if we weren't removed from that environment we would die. If there were no photosynthesizers on Earth, the same thing would happen to our atmosphere, but it would take thousands of years. But it is not just the air that gets changed according to Lovelock.

Evidence... shows the Earth's crust, oceans, and air to be either directly the product of living things or else massively modified by their presence. Consider how the oxygen and nitrogen from the air come directly from plants and microorganisms and how the chalk and limestone rocks are the shells of living things once floating in the sea.

To summarize so far: James Lovelock has listed four significant properties of life which I call:

  1. The Goldilocks property
  2. The Kudzu property
  3. Darwinian natural selection
  4. Life's ability to change its environment

These four properties are the main ingredients of a recipe for “Gaia” according to Lovelock. What exactly is Gaia? And who is James Lovelock?

“Gaia” is the Greek name for the mythical Mother- Earth goddess. Lovelock used that name to call the Earth, seen as a single physiological system, an entity, ... that is alive, at least to the extent like other organisms, its chemistry and temperature are self-regulated at a state favourable for its inhabitants.

Gaia is an evolving system, a system made up from all living things and their surface environment, the oceans, atmosphere, and crustal rocks, the two parts tightly coupled and indivisible. It is an 'emergent domain' – a system that has emerged from the reciprocal evolution of organisms and their environment over aeons of life on Earth. In this system the self-regulation of climate and chemical composition are entirely automatic. Self- regulation emerges as the system evolves. No foresight, planning, or teleology are involved.

James Lovelock is a British scientist who invented several devices that measured the presence and amount of trace gases in the atmosphere. In the 1960's he got a job working for NASA at the Jet Propulsion Lab in Pasadena California. At the time, one of NASA's goals was to discover whether or not there is life on Mars. Lovelock, after thinking about the problem, realized that the easiest way to tell whether there was life on Mars was by examining its atmosphere – which could be done without actually sending a rocket into space. Needless to say, this was not a popular point of view at NASA because their main purpose is to send rockets into space.

I argued that if there was life on Mars it would have to use the atmosphere as a source of raw materials and as somewhere to deposit its wastes; this would change the atmosphere's composition and make it recognizably different from a dead planet.

Since the atmosphere of Mars is ninety per cent carbon dioxide, there is no methane, and only trace amounts of oxygen, Mars is chemically inert and very stable. On Earth there is oxygen and methane in the atmosphere, which means that Earth's atmosphere is chemically unstable. Over time free oxygen will combine with the surface rocks and with hydrogen in a process called oxidization. Only the continued existence of life could keep that proportion of oxygen in the atmosphere stable over time. On Mars there is no life. You may recall that I said that when life first began on Earth the atmosphere was mostly carbon dioxide with almost no oxygen, which, it turns out, is the same atmosphere as Mars has now. There is very little water on Mars, but there is evidence that there used to be water on Mars. Lovelock argues that it is the presence of life on Earth that is the reason Earth has water and it is the absence of life that has led to Venus and Mars losing theirs. It is the presence of life that changed Earth's atmosphere to what it is today, hence it is the absence of life that left the atmosphere of Venus and Mars unchanged.

One of the most popular photographs, perhaps the most popular photograph ever, is a snapshot taken by an astronaut of the Earth – from the window of an Apollo spacecraft as it journeyed from the Earth to the Moon. You can see Antarctica, almost all of Africa, the Arabian peninsula, the South Atlantic and Indian Oceans and a massive weather system in the Southern Ocean. This picture has had a profound effect on many people. We all live here on Earth but it's difficult to see the bigger picture because we are in the midst of it. But this particular photograph changed many peoples' perspective. In James Lovelock's view, see the Earth from space forces questions about the composition of the air we breathe not previously asked.
For instance:

......Why is everything on our planet so comfortable and well suited for life? .......The air is a mixture that almost always keeps constant in composition. My flash of enlightenment that afternoon was the thought that to keep constant something must be regulating it and that somehow the life on the surface was involved.

A living cell regulates its internal environment – keeping its salt content at .9% and all the other essential elements at various optimal concentrations. This it does in spite of changes in the external environment..... up to a point. If the environmental changes are too severe - if the salt content of the water bathing the cell reaches 6% the cell dies. And the same thing happens if the salt content of the water bathing the cell becomes too low. Life is bound by constraints. And if those constraints are breached life perishes.

A cell cannot regulate its internal temperature because it is too small. But multi-cellular organisms can. Cold-blooded animals do not regulate their body temperature internally but they can do it by changing their behaviour – by seeking the sunlight to raise their temperature and seeking shade in order to lower their temperature. Warm-blooded animals can also regulate their temperature through behaviour. Birds in the northern hemisphere fly south for the winter. People make clothes and build houses.

Our bodies regulate our temperatures by a complex interconnecting system of internal organs. When we are cold our autonomic nervous system causes our muscles to twitch uncontrollably – this is called shivering. The blood vessels near the skin surface constrict, keeping the majority of blood in the body's well-insulated core. When we are hot the blood vessels in the extremities open up, passing the body's heat into the surrounding air. Glands in our skin secrete sweat and this cools our bodies through the evaporation of water. You get the picture. Although no solitary cell is able to regulate its internal temperature, over vast spans of time, life has evolved the ability to do this because it enhances an organism's survival.

Now we are a life form, a part of Gaia, and like Kudzu we have thrived and our population has expanded until we have filled our biological niche. But there is a big difference between us and other form s of life. Because we use automobiles and many other kinds of machines, we are magnifying our environmental effects on Gaia manyfold. We are producing so much carbon dioxide that it's affecting the global climate. By now most everybody except a President and a couple of Prime Ministers believe this to be the case. But suppose Lovelock is right and Gaia is a self-regulating entity. Then we have just fooled with Gaia's thermostat. By continuing with business as usual we will be undermining Gaia's ability to repair herself and ultimately to support us. The consequences are likely to be very unpleasant and we have very little time to correct what we have done.

Scientists predict a rise in global mean temperature of as much as five degrees centigrade in this coming century. However, they may have underestimated the projected rise in temperature because many of the climate change models leave out positive feedback effects.

There are several positive feedback mechanisms that could come into play in a hotter world. One is the “albedo” or reflective capacity of the Earth's surface. Ice has a high albedo – it reflects the Sun's rays and helps keep the Earth cool. Open water has a low albedo – it absorbs heat from the Sun. As sea ice melts away and as the Earth's glaciers shrink in size, the Earth's albedo will decrease causing an acceleration of warming.

There is frozen methane at the bottom of the Arctic Ocean and locked away in the Arctic permafrost. If it were to melt, we would have significant increases in the amount of methane which is an even stronger greenhouse gas causing more global warming.

There is the problem of forest fires. As temperatures increase more moisture evaporates from the soil leaving forests dryer and more prone to catch fire. As more forests burn more carbon dioxide is released into the air causing yet more global warming.

There is the ocean plankton. Plankton consists of microscopic algae and animal life that forms the basis of the oceans food chains. It gets its sunlight because it is always in the surface waters. It gets nutrients from the deep waters that form upwellings along the continental shelves. As the temperature of the surface waters increases, the top layer of warm water expands, thus growing lighter. This locks away the heavier colder nutrient-rich waters deep underneath, decreasing the upwelling and starving the plankton of nutrients. Result: less carbon dioxide will be absorbed and sea life in general will decline.

Finally there is the solubility of carbon dioxide in water. The warmer the water the less soluble is carbon dioxide. As the temperature of the oceans increases they will release carbon dioxide into the atmosphere increasing the amount of global warming. Note, that when the oceans are cooler they have the opposite effect, they act as a negative feedback on global warming by absorbing carbon dioxide.

About these positive feedbacks to global warming there is nothing we can do.... On the other hand, there is one way of reversing global warming that we do have control over. We can decrease our use of fossil fuels. By doing this we may be able to limit global warming before it becomes a runaway process.

The solutions are all around us – small-scale hydro, solar and wind power, tidal power, wave power, nuclear power, increasing household energy efficiency, local community supported agriculture, investing in mass transit, bicycles, recycling, walking.

Global warming is not just a problem for some people. It is a risk to the entire human race. It therefore has the potential to unify human society because no-one can escape it. Like the Boxing Day, 2004 tsunami in Banda Aceh that led to the end of a civil war, when enough people realize that Global Warming threatens everyone we will unite in order to save our future.

One of our key problems is inertia. It is natural to overestimate the cost of change and underestimate the cost of doing nothing. It's not just President Bush who did this. We all do it. Think of the decision to get out of bed on a cold morning. The idea of throwing off the covers and braving the cold can seem daunting . Yet, when we finally do it it's no big deal. What paralyzes us is the perception of being cold, not the reality.

James Lovelock concludes his latest book, The Revenge of Gaia, by

.....Our task as individuals is to think of Gaia first. In no way does this make us inhuman or uncaring; our survival as a species is wholly dependent on Gaia and on our acceptance of her discipline.

The human race now faces the greatest challenge in history. We've already seen how denial and ignorance can bring out the worst. If people unite to face this challenge it can bring out the best in us. I want to conclude with the words of Al Gore from his book “An Inconvenient Truth”:

The climate crisis also offers us the chance to experience what very few generations in history have had the privilege of knowing – a generational mission; the exhilaration of compelling moral purpose; a shared and unifying cause. The thrill of being forced by circumstances to put aside the pettiness and conflict that so often stifle the restless human need for transcendence, the opportunity to rise...

It is about who we are as human beings. It is about our capacity to transcend our own limitations, to rise to the new occasion, to see with our hearts, as well as our heads, the response that is now called for. This is a moral, ethical, and spiritual challenge.We should fear this challenge. We should welcome it. We must not wait. In the words of Dr. King, “tomorrow is today.”

c. 2006 by Charles Justice

Books Quoted:

James Lovelock, Gaia: A New Look at Life on Earth
Oxford University Press, 1979.

James Lovelock, The Ages of Gaia: A Biography of the Living Earth
WW Norton, New York, 1988.

James Lovelock, The Revenge of Gaia
Penguin Books, 2006.

Al Gore, An Inconvenient Truth
Rodale Press, 2006.

No comments:

Post a Comment