The rise in carbon levels was not - contrary to popular opinion - a recent event, although our ever-increasing technology has made the situation worse with each passing decade. The internal combustion engine was invented in the 1860s - the days of our great grandparents. It was the beginning of the Industrial Revolution, and in 1860, we released about 93 million tons of carbon into the air.

Between 1860 and 1958, industry burned fossil fuels at a rate that doubled every two decades or so, injecting a total of more than 76 billion tons of carbon into the air. Almost 80 billion tons of carbon went into the air between 1860 and 1960. Since 1960, another 80 billion tons have been added. It took one hundred years to release the first half of the fossil carbon found in the atmosphere today; it took less than thirty years to release as much again. Human beings are now releasing more than 5 billion tons of carbon into the air each year.

The Industrial Revolution threw the human sphere into high gear; people began burning more coal and charcoal to fuel the engines and to smelt steel to make more engines. They kilned clamshells and limestone to make lime for concrete for more and more factories, cities, roads between cities. They built better engines that did more work and they fed them more coal, oil, and natural gas, in a crescendo of carbon dioxide that is still building today. In effect, every human being on the planet is now shoveling one ton of carbon into the air each year.

The temperature of the planet may be rising as well. These two changes in the atmosphere are presumed to have triggered the change in life's breathing cycle; it makes sense that the changes that are taking place on the planet would show up first in the breathing of the planet itself, which is the grand summation of all of the action of life on Earth.

With

A Flemish alchemist and physician named Johann Baptista van Helmont was the first man to discover that the air we breathe is not one single substance but a mixture of substances. In a manuscript published after his death in 1644, he argued, based on his experiments, that an invisible "spirit" curled from every one of the bubbling flasks in his alchemical laboratory, and from each of the red coals in his furnaces. "I call this Spirit, unknown hitherto, by the new name of Gas," he wrote - coining the word from the Flemish pronunciation of the Greek word "chaos." One of the gases that he discovered was carbon dioxide, a gas that is now creating chaos on a global level.

Since van Helmont's discovery, we have come to realize, through scientific experimentation and persistent measurements, that carbon dioxide is almost everywhere. By the 1950s, Charles Keeling, working under the auspices of the California Institute of Technology, began extensive tracking of carbon dioxide levels on the planet. He recognized a pattern that had eluded others: the carbon dioxide concentration always dropped as the sun rose in the sky, and then in- creased as the sun went down. The count stayed high all night, bottomed out in the afternoon, and began climbing again after sundown.

The life cycle was becoming more and more obvious to the scientific community: every day, as the sun rises, every green thing on the planet - from skunk cabbage to club moss - begins inhaling carbon dioxide, for use in photosynthesis. As the plants inhale, the amount of gas in the air begins to drop.

Photosynthesis is, literally, "building with light." The building process takes place inside plant cells within organelles call chloroplasts. Inside each choloroplast, plants break apart molecules of carbon dioxide into carbon and oxygen. They also break water molecules into hydrogen and oxygen. Then they put most of these atoms back together in new combinations to build simple sugars like glucose, throwing out some of the oxygen as "trash." The process requires steady supplies of sunlight for energy, and steady supplies of carbon dioxide and water for raw materials.

By afternoon, plants have taken a good deal of carbon dioxide out of the atmosphere. At the same time, however, the plants are busily eating the sugars they have made for themselves. This is the metabolic process of respiration. Respiration means literally "to breathe back, to blow back;" it is a form of combustion, a very slow burn which consumes oxygen and produces carbon dioxide.

Photosynthesis and respiration are two of the most fundamental processes of life on Earth, and they run in opposite directions. Photosynthesis takes in carbon dioxide and releases oxygen; respiration takes in oxygen and releases carbon di- oxide. The two processes also run on different timetables: photosynthesis works a day shift, because the process requires sunlight and most plants take in carbon dioxide only when the sun shines. The gas enters the plant through a myriad of microscopic pores, stomata, on the underside of each green leaf. These little doors open at sunrise and close at sundown on every plant on the planet.

Respiration, on the other hand, works both a day shift and a night shift. At four o'clock in the morning - while the stomata are closed and green leaves are taking in virtually no carbon dioxide - the leaves are still respiring, blowing back carbon dioxide to the air. At the close of most twenty-four hour periods, most plants have "borrowed from and returned to" the atmosphere about the same amount of carbon dioxide.

This "breathing cycle" is apparent throughout the plant life on the planet: plants and trees breathe once a day. (Animals, including people, aren't a natural part of this cycle. They have no cholorplasts, so they get their energy and their raw materials by eating plants, and by eating the animals that have eaten plants, and by inhaling the oxygen released by plants.)

So?

So this natural breathing cycle of the earth's plant life is a major factor in one of the major ecological problems facing the planet: the greenhouse effect.

It is the atmosphere that keeps us warm; outer space is a very cold place, and it is the layers of gases that wrap the planet that protect us from freezing. In this sense, the Earth's gases are like the glass walls of a greenhouse.

The gases which have the highest volume in the atmosphere are not the gases that are having the most powerful greenhouse effect. Nitrogen and oxygen - which constitute 99% of the atmosphere - have almost no greenhouse effect at all. The three gases that DO have a major effect are water vapor, carbon dioxide, and ozone.

Like nitrogen and oxygen, these three gases are almost perfectly transparent to the sunlight that streams to the Earth from the Sun. However, water vapor, carbon dioxide, and ozone are partially opaque to the infrared heat radiation that rises from the sun-baked ground.

When this infrared radiation strikes the water vapor, carbon dioxide or ozone molecules, the molecules give off energy in the form of more infrared rays. In a sense, every carbon dioxide molecule in the atmosphere is like a dark star shining in all directions - up, down, and sideways. In this way, invisible rays of energy get passed back and forth many times between the atmosphere and the layers of the planet before the energy finally migrates to the top of the atmosphere and escapes into the vacuum of outer space.

That is the greenhouse effect in a nutshell: the dark rays bounce around inside the atmosphere many times before they finally manage to leak out into space. Water vapor, carbon dioxide, and ozone - rare though they are - turn the world's air into a giant heat trap. And for billions of years, life on Earth has been dependent on this peculiar property of these three gases (and a few others that are even rarer) to keep the planet livable.

The carbon dioxide level in the atmosphere is a vital ingredient in the natural life cycle of the planet and the life forms it contains; if the amount of carbon dioxide varies by too much, the results on the planet could be disastrous. A minute drop, the scientists discovered, could chill the entire planet, and may have been the force behind the last Ice Age.

But what are the effects of a rise in the carbon dioxide count? As early as the 1890s, scientists predicted that this change could very well heat the planet to heights outside all human experience. It became increasing clear that the problem lay not in a possible drop in the carbon dioxide levels, but in a rise - based on new technology that introduced tons of carbon dioxide into the atmosphere - that would change the atmosphere itself. Any change in the atmosphere would, of necessity, change the life cycles themselves.

Beyond the daily photosynthesis/respiration cycle is a larger cycle. To understand it, we need to enlarge our vision to include the whole pageantry of the seasons, the annual passage of foliage from green to red and yellow to brown and black, in terms of invisible effects. Plants take up carbon dioxide mainly in the spring and summer, their green and busy season. They drop their leaves in the fall. The leaves wither and decay, and the carbon that the plants had borrowed from the air that summer returns to the air.

Here again, photosynthesis and respiration march to different drummers. Photosynthesis is mostly a thing of summer. It begins in April, peaks in June, and drops near zero in October, when there is too little sunlight. In other words, it runs hard during the light part of the year and all but quits during the dark part of the year.

Respiration peaks in June, too, but unlike photosynthesis it never stops (except where the ground is frozen) - it keeps on going, throughout the winter and all year round. The life forms that decompose the fallen leaves include fungi, bacteria, worms, termites, slugs, and leaf molds. They compete to eat the dead leaves, to rot the fallen branches, and together they return most of life's borrowed carbon to the air.

Every year, when green things inhale carbon to put out buds, shoots, leaves and stems, the biosphere inhales. When the leaves fall and molder on the ground, the biosphere exhales. In the most beautiful, regular and global cycles in nature, the planet itself takes one breath a year. It is that breathing pattern that has been put at risk by the rise in carbon dioxide levels.

The atmospheric counts for the years since the 1950s show a definitive pattern: each fall, there is a rise in the record. Each summer, there is a dip in the record. Each winter, the high is higher than it was the winter before. The impact is clear.

The breath of life on this planet is changing. Since the 1970s, the breathing of the biosphere is no longer regular. The Earth's inhalations and exhalations seem to be getting bigger and bigger. We know it's happening, but we're not sure why, and we're not sure what the long-term effect will be. We do know that the amount of carbon dioxide in the air is rising.

The rise in carbon levels was not - contrary to popular opinion - a recent event, although our ever-increasing technology has made the situation worse with each passing decade. The internal combustion engine was invented in the 1860s - the days of our great grandparents. It was the beginning of the Industrial Revolution, and in 1860, we released about 93 million tons of carbon into the air.

Between 1860 and 1958, industry burned fossil fuels at a rate that doubled every two decades or so, injecting a total of more than 76 billion tons of carbon into the air. Almost 80 billion tons of carbon went into the air between 1860 and 1960. Since 1960, another 80 billion tons have been added. It took one hundred years to release the first half of the fossil carbon found in the atmosphere today; it took less than thirty years to release as much again. Human beings are now releasing more than 5 billion tons of carbon into the air each year.

The Industrial Revolution threw the human sphere into high gear; people began burning more coal and charcoal to fuel the engines and to smelt steel to make more engines. They kilned clamshells and limestone to make lime for concrete for more and more factories, cities, roads between cities. They built better engines that did more work and they fed them more coal, oil, and natural gas, in a crescendo of carbon dioxide that is still building today. In effect, every human being on the planet is now shoveling one ton of carbon into the air each year.

The temperature of the planet may be rising as well. These two changes in the atmosphere are presumed to have triggered the change in life's breathing cycle; it makes sense that the changes that are taking place on the planet would show up first in the breathing of the planet itself, which is the grand summation of all of the action of life on Earth.

With e

By afternoon, plants have taken a good deal of carbon dioxide out of the atmosphere. At the same time, however, the plants are busily eating the sugars they have made for themselves. This is the metabolic process of respiration. Respiration means literally "to breathe back, to blow back;" it is a form of combustion, a very slow burn which consumes oxygen and produces carbon dioxide.

Photosynthesis and respiration are two of the most fundamental processes of life on Earth, and they run in opposite directions. Photosynthesis takes in carbon dioxide and releases oxygen; respiration takes in oxygen and releases carbon di- oxide. The two processes also run on different timetables: photosynthesis works a day shift, because the process requires sunlight and most plants take in carbon dioxide only when the sun shines. The gas enters the plant through a myriad of microscopic pores, stomata, on the underside of each green leaf. These little doors open at sunrise and close at sundown on every plant on the planet.

Respiration, on the other hand, works both a day shift and a night shift. At four o'clock in the morning - while the stomata are closed and green leaves are taking in virtually no carbon dioxide - the leaves are still respiring, blowing back carbon dioxide to the air. At the close of most twenty-four hour periods, most plants have "borrowed from and returned to" the atmosphere about the same amount of carbon dioxide.

This "breathing cycle" is apparent throughout the plant life on the planet: plants and trees breathe once a day. (Animals, including people, aren't a natural part of this cycle. They have no cholorplasts, so they get their energy and their raw materials by eating plants, and by eating the animals that have eaten plants, and by inhaling the oxygen released by plants.)

So?

So this natural breathing cycle of the earth's plant life is a major factor in one of the major ecological problems facing the planet: the greenhouse effect.

It is the atmosphere that keeps us warm; outer space is a very cold place, and it is the layers of gases that wrap the planet that protect us from freezing. In this sense, the Earth's gases are like the glass walls of a greenhouse.

The gases which have the highest volume in the atmosphere are not the gases that are having the most powerful greenhouse effect. Nitrogen and oxygen - which constitute 99% of the atmosphere - have almost no greenhouse effect at all. The three gases that DO have a major effect are water vapor, carbon dioxide, and ozone.

Like nitrogen and oxygen, these three gases are almost perfectly transparent to the sunlight that streams to the Earth from the Sun. However, water vapor, carbon dioxide, and ozone are partially opaque to the infrared heat radiation that rises from the sun-baked ground.

When this infrared radiation strikes the water vapor, carbon dioxide or ozone molecules, the molecules give off energy in the form of more infrared rays. In a sense, every carbon dioxide molecule in the atmosphere is like a dark star shining in all directions - up, down, and sideways. In this way, invisible rays of energy get passed back and forth many times between the atmosphere and the layers of the planet before the energy finally migrates to the top of the atmosphere and escapes into the vacuum of outer space.

That is the greenhouse effect in a nutshell: the dark rays bounce around inside the atmosphere many times before they finally manage to leak out into space. Water vapor, carbon dioxide, and ozone - rare though they are - turn the world's air into a giant heat trap. And for billions of years, life on Earth has been dependent on this peculiar property of these three gases (and a few others that are even rarer) to keep the planet livable.

The carbon dioxide level in the atmosphere is a vital ingredient in the natural life cycle of the planet and the life forms it contains; if the amount of carbon dioxide varies by too much, the results on the planet could be disastrous. A minute drop, the scientists discovered, could chill the entire planet, and may have been the force behind the last Ice Age.

But what are the effects of a rise in the carbon dioxide count? As early as the 1890s, scientists predicted that this change could very well heat the planet to heights outside all human experience. It became increasing clear that the problem lay not in a possible drop in the carbon dioxide levels, but in a rise - based on new technology that introduced tons of carbon dioxide into the atmosphere - that would change the atmosphere itself. Any change in the atmosphere would, of necessity, change the life cycles themselves.

Beyond the daily photosynthesis/respiration cycle is a larger cycle. To understand it, we need to enlarge our vision to include the whole pageantry of the seasons, the annual passage of foliage from green to red and yellow to brown and black, in terms of invisible effects. Plants take up carbon dioxide mainly in the spring and summer, their green and busy season. They drop their leaves in the fall. The leaves wither and decay, and the carbon that the plants had borrowed from the air that summer returns to the air.

Here again, photosynthesis and respiration march to different drummers. Photosynthesis is mostly a thing of summer. It begins in April, peaks in June, and drops near zero in October, when there is too little sunlight. In other words, it runs hard during the light part of the year and all but quits during the dark part of the year.

Respiration peaks in June, too, but unlike photosynthesis it never stops (except where the ground is frozen) - it keeps on going, throughout the winter and all year round. The life forms that decompose the fallen leaves include fungi, bacteria, worms, termites, slugs, and leaf molds. They compete to eat the dead leaves, to rot the fallen branches, and together they return most of life's borrowed carbon to the air.

Every year, when green things inhale carbon to put out buds, shoots, leaves and stems, the biosphere inhales. When the leaves fall and molder on the ground, the biosphere exhales. In the most beautiful, regular and global cycles in nature, the planet itself takes one breath a year. It is that breathing pattern that has been put at risk by the rise in carbon dioxide levels.

The atmospheric counts for the years since the 1950s show a definitive pattern: each fall, there is a rise in the record. Each summer, there is a dip in the record. Each winter, the high is higher than it was the winter before. The impact is clear.

The breath of life on this planet is changing. Since the 1970s, the breathing of the biosphere is no longer regular. The Earth's inhalations and exhalations seem to be getting bigger and bigger. We know it's happening, but we're not sure why, and we're not sure what the long-term effect will be. We do know that the amount of carbon dioxide in the air is rising.

The rise in carbon levels was not - contrary to popular opinion - a recent event, although our ever-increasing technology has made the situation worse with each passing decade. The internal combustion engine was invented in the 1860s - the days of our great grandparents. It was the beginning of the Industrial Revolution, and in 1860, we released about 93 million tons of carbon into the air.

Between 1860 and 1958, industry burned fossil fuels at a rate that doubled every two decades or so, injecting a total of more than 76 billion tons of carbon into the air. Almost 80 billion tons of carbon went into the air between 1860 and 1960. Since 1960, another 80 billion tons have been added. It took one hundred years to release the first half of the fossil carbon found in the atmosphere today; it took less than thirty years to release as much again. Human beings are now releasing more than 5 billion tons of carbon into the air each year.

The Industrial Revolution threw the human sphere into high gear; people began burning more coal and charcoal to fuel the engines and to smelt steel to make more engines. They kilned clamshells and limestone to make lime for concrete for more and more factories, cities, roads between cities. They built better engines that did more work and they fed them more coal, oil, and natural gas, in a crescendo of carbon dioxide that is still building today. In effect, every human being on the planet is now shoveling one ton of carbon into the air each year.

The temperature of the planet may be rising as well. These two changes in the atmosphere are presumed to have triggered the change in life's breathing cycle; it makes sense that the changes that are taking place on the planet would show up first in the breathing of the planet itself, which is the grand summation of all of the action of life on Earth.

With

The gases which have the highest volume in the atmosphere are not the gases that are having the most powerful greenhouse effect. Nitrogen and oxygen - which constitute 99% of the atmosphere - have almost no greenhouse effect at all. The three gases that DO have a major effect are water vapor, carbon dioxide, and ozone.

Like nitrogen and oxygen, these three gases are almost perfectly transparent to the sunlight that streams to the Earth from the Sun. However, water vapor, carbon dioxide, and ozone are partially opaque to the infrared heat radiation that rises from the sun-baked ground.

When this infrared radiation strikes the water vapor, carbon dioxide or ozone molecules, the molecules give off energy in the form of more infrared rays. In a sense, every carbon dioxide molecule in the atmosphere is like a dark star shining in all directions - up, down, and sideways. In this way, invisible rays of energy get passed back and forth many times between the atmosphere and the layers of the planet before the energy finally migrates to the top of the atmosphere and escapes into the vacuum of outer space.

That is the greenhouse effect in a nutshell: the dark rays bounce around inside the atmosphere many times before they finally manage to leak out into space. Water vapor, carbon dioxide, and ozone - rare though they are - turn the world's air into a giant heat trap. And for billions of years, life on Earth has been dependent on this peculiar property of these three gases (and a few others that are even rarer) to keep the planet livable.

The carbon dioxide level in the atmosphere is a vital ingredient in the natural life cycle of the planet and the life forms it contains; if the amount of carbon dioxide varies by too much, the results on the planet could be disastrous. A minute drop, the scientists discovered, could chill the entire planet, and may have been the force behind the last Ice Age.

But what are the effects of a rise in the carbon dioxide count? As early as the 1890s, scientists predicted that this change could very well heat the planet to heights outside all human experience. It became increasing clear that the problem lay not in a possible drop in the carbon dioxide levels, but in a rise - based on new technology that introduced tons of carbon dioxide into the atmosphere - that would change the atmosphere itself. Any change in the atmosphere would, of necessity, change the life cycles themselves.

Beyond the daily photosynthesis/respiration cycle is a larger cycle. To understand it, we need to enlarge our vision to include the whole pageantry of the seasons, the annual passage of foliage from green to red and yellow to brown and black, in terms of invisible effects. Plants take up carbon dioxide mainly in the spring and summer, their green and busy season. They drop their leaves in the fall. The leaves wither and decay, and the carbon that the plants had borrowed from the air that summer returns to the air.

Here again, photosynthesis and respiration march to different drummers. Photosynthesis is mostly a thing of summer. It begins in April, peaks in June, and drops near zero in October, when there is too little sunlight. In other words, it runs hard during the light part of the year and all but quits during the dark part of the year.

Respiration peaks in June, too, but unlike photosynthesis it never stops (except where the ground is frozen) - it keeps on going, throughout the winter and all year round. The life forms that decompose the fallen leaves include fungi, bacteria, worms, termites, slugs, and leaf molds. They compete to eat the dead leaves, to rot the fallen branches, and together they return most of life's borrowed carbon to the air.

Every year, when green things inhale carbon to put out buds, shoots, leaves and stems, the biosphere inhales. When the leaves fall and molder on the ground, the biosphere exhales. In the most beautiful, regular and global cycles in nature, the planet itself takes one breath a year. It is that breathing pattern that has been put at risk by the rise in carbon dioxide levels.

The atmospheric counts for the years since the 1950s show a definitive pattern: each fall, there is a rise in the record. Each summer, there is a dip in the record. Each winter, the high is higher than it was the winter before. The impact is clear.

The breath of life on this planet is changing. Since the 1970s, the breathing of the biosphere is no longer regular. The Earth's inhalations and exhalations seem to be getting bigger and bigger. We know it's happening, but we're not sure why, and we're not sure what the long-term effect will be. We do know that the amount of carbon dioxide in the air is rising.

The rise in carbon levels was not - contrary to popular opinion - a recent event, although our ever-increasing technology has made the situation worse with each passing decade. The internal combustion engine was invented in the 1860s - the days of our great grandparents. It was the beginning of the Industrial Revolution, and in 1860, we released about 93 million tons of carbon into the air.

Between 1860 and 1958, industry burned fossil fuels at a rate that doubled every two decades or so, injecting a total of more than 76 billion tons of carbon into the air. Almost 80 billion tons of carbon went into the air between 1860 and 1960. Since 1960, another 80 billion tons have been added. It took one hundred years to release the first half of the fossil carbon found in the atmosphere today; it took less than thirty years to release as much again. Human beings are now releasing more than 5 billion tons of carbon into the air each year.

The Industrial Revolution threw the human sphere into high gear; people began burning more coal and charcoal to fuel the engines and to smelt steel to make more engines. They kilned clamshells and limestone to make lime for concrete for more and more factories, cities, roads between cities. They built better engines that did more work and they fed them more coal, oil, and natural gas, in a crescendo of carbon dioxide that is still building today. In effect, every human being on the planet is now shoveling one ton of carbon into the air each year.

The temperature of the planet may be rising as well. These two changes in the atmosphere are presumed to have triggered the change in life's breathing cycle; it makes sense that the changes that are taking place on the planet would show up first in the breathing of the planet itself, which is the grand summation of all of the action of life on Earth.

With

Beyond the daily photosynthesis/respiration cycle is a larger cycle. To understand it, we need to enlarge our vision to include the whole pageantry of the seasons, the annual passage of foliage from green to red and yellow to brown and black, in terms of invisible effects. Plants take up carbon dioxide mainly in the spring and summer, their green and busy season. They drop their leaves in the fall. The leaves wither and decay, and the carbon that the plants had borrowed from the air that summer returns to the air.

Here again, photosynthesis and respiration march to different drummers. Photosynthesis is mostly a thing of summer. It begins in April, peaks in June, and drops near zero in October, when there is too little sunlight. In other words, it runs hard during the light part of the year and all but quits during the dark part of the year.

Respiration peaks in June, too, but unlike photosynthesis it never stops (except where the ground is frozen) - it keeps on going, throughout the winter and all year round. The life forms that decompose the fallen leaves include fungi, bacteria, worms, termites, slugs, and leaf molds. They compete to eat the dead leaves, to rot the fallen branches, and together they return most of life's borrowed carbon to the air.

Every year, when green things inhale carbon to put out buds, shoots, leaves and stems, the biosphere inhales. When the leaves fall and molder on the ground, the biosphere exhales. In the most beautiful, regular and global cycles in nature, the planet itself takes one breath a year. It is that breathing pattern that has been put at risk by the rise in carbon dioxide levels.

The atmospheric counts for the years since the 1950s show a definitive pattern: each fall, there is a rise in the record. Each summer, there is a dip in the record. Each winter, the high is higher than it was the winter before. The impact is clear.

The breath of life on this planet is changing. Since the 1970s, the breathing of the biosphere is no longer regular. The Earth's inhalations and exhalations seem to be getting bigger and bigger. We know it's happening, but we're not sure why, and we're not sure what the long-term effect will be. We do know that the amount of carbon dioxide in the air is rising.

The rise in carbon levels was not - contrary to popular opinion - a recent event, although our ever-increasing technology has made the situation worse with each passing decade. The internal combustion engine was invented in the 1860s - the days of our great grandparents. It was the beginning of the Industrial Revolution, and in 1860, we released about 93 million tons of carbon into the air.

Between 1860 and 1958, industry burned fossil fuels at a rate that doubled every two decades or so, injecting a total of more than 76 billion tons of carbon into the air. Almost 80 billion tons of carbon went into the air between 1860 and 1960. Since 1960, another 80 billion tons have been added. It took one hundred years to release the first half of the fossil carbon found in the atmosphere today; it took less than thirty years to release as much again. Human beings are now releasing more than 5 billion tons of carbon into the air each year.

The Industrial Revolution threw the human sphere into high gear; people began burning more coal and charcoal to fuel the engines and to smelt steel to make more engines. They kilned clamshells and limestone to make lime for concrete for more and more factories, cities, roads between cities. They built better engines that did more work and they fed them more coal, oil, and natural gas, in a crescendo of carbon dioxide that is still building today. In effect, every human being on the planet is now shoveling one ton of carbon into the air each year.

The temperature of the planet may be rising as well. These two changes in the atmosphere are presumed to have triggered the change in life's breathing cycle; it makes sense that the changes that are taking place on the planet would show up first in the breathing of the planet itself, which is the grand summation of all of the action of life on Earth.

With

The rise in carbon levels was not - contrary to popular opinion - a recent event, although our ever-increasing technology has made the situation worse with each passing decade. The internal combustion engine was invented in the 1860s - the days of our great grandparents. It was the beginning of the Industrial Revolution, and in 1860, we released about 93 million tons of carbon into the air.

Between 1860 and 1958, industry burned fossil fuels at a rate that doubled every two decades or so, injecting a total of more than 76 billion tons of carbon into the air. Almost 80 billion tons of carbon went into the air between 1860 and 1960. Since 1960, another 80 billion tons have been added. It took one hundred years to release the first half of the fossil carbon found in the atmosphere today; it took less than thirty years to release as much again. Human beings are now releasing more than 5 billion tons of carbon into the air each year.

The Industrial Revolution threw the human sphere into high gear; people began burning more coal and charcoal to fuel the engines and to smelt steel to make more engines. They kilned clamshells and limestone to make lime for concrete for more and more factories, cities, roads between cities. They built better engines that did more work and they fed them more coal, oil, and natural gas, in a crescendo of carbon dioxide that is still building today. In effect, every human being on the planet is now shoveling one ton of carbon into the air each year.

The temperature of the planet may be rising as well. These two changes in the atmosphere are presumed to have triggered the change in life's breathing cycle; it makes sense that the changes that are taking place on the planet would show up first in the breathing of the planet itself, which is the grand summation of all of the action of life on Earth.

With every year that passes, geochemists are discovering more and more changes in the workings of the planet, and trying - desperately - to figure out what it all means. Without disentangling cause and effect, they can't all agree that the changes are alarming. With the breathing of the world, these are a few of the perspectives being offered:

GROWTH. The green plants of the biosphere LIKE the extra carbon dioxide we are putting into the air. It gives them more raw material for photosynthesis. Each year the biosphere gets bigger; because it is bigger it takes in more carbon dioxide. It inhales more and more deeply.

DECAY: The biosphere is decaying faster than before. There is more and more respiration each winter. Each year it inhales a little more. More and more of the "stuff of life" is unraveling and returning to the air.

GROWTH AND DECAY: Both may be accelerating. A bigger biosphere would be expected to inhale and exhale more deeply. Each summer there are more plants to inhale gas; each winter there may be more plants and animals to devour and de- compose the summer's fruits.

TIMING: Some say the change can't be explained with either growth or decay. The breathing of the world is changing too fast for that. Something else is going on; some suggest that the build-up of carbon dioxide in the atmosphere may be altering the timing of either photosynthesis or respiration or both. If their work schedules are changing positions on the calendar, that would also change the breathing of the world.

Technological optimists tend to feel that the Earth is breathing more deeply. The biosphere LIKES the extra carbon dioxide. To this perspective, life on the planet Earth is flourishing.

Technological pessimists tend to feel that life's breath is labored - each year more labored than the year before. The biosphere is running out of breath; the Earth is gasping.

Were we to chart the carbon dioxide levels on the planet as they are now, and as they would have been without the Industrial Revolution, we would have a clear picture of what we have done in the name of progress. One line would show the balance of nature; the other would show our species in the act of unbalancing nature. Here, the sum of life on Earth; there, the sum of our impact upon life on Earth. These two lines would bring the present human predicament, in all it's diversity, into the sharpest possible focus.

It is, after all, a matter of life and breath.