Both the atmosphere and the oceans continuously exchange carbon dioxide with rocks and with living organisms [see illustration on pages 44–45]. They gain carbon dioxide from the volcanic activity that releases gases from the earth's interior and from the respiration and decay of organisms; they lose carbon dioxide to the weathering of rock and the photosynthesis of plants. As these processes change pace, the content of carbon dioxide in the atmosphere also changes, shifting the radiation balance and raising or lowering the earth's temperature.
Of course during any particular geologic era other factors may influence climate. Nonetheless let us examine some of the known facts of geological history and see how many can be explained in terms of variation in the carbon dioxide content of the atmosphere.
Studies of rock strata reveal that for the past billion years most of the world has had a tropical climate. Every 250 million years or so this tropical spell is broken by relatively short glacial periods which bury a substantial portion of the earth under ice sheets. These cool periods last several million years, during which the glaciers retreat and advance many times as the temperature rises and falls. During the last 620,000 years of the current glacial epoch, for example, deep ocean sediments show 10 distinct temperature cycles. The carbon dioxide theory may well account for these temperature fluctuations.
A decline in the carbon dioxide concentration in the atmosphere–ocean system—and a period of decline in worldwide temperature—may be induced by a number of developments. The rate of volcanic activity could slow down as the rate of rock weathering increased, or an especially flourishing mantle of vegetation could take up huge quantities of carbon dioxide and form new coal beds and other organic deposits in marshy areas. After a geologically short time, the adjustment of the atmosphere–ocean equilibrium to the leaner supply of carbon dioxide could bring the atmospheric concentration down to .015 per cent, half its present value. Calculations show that a 50-per cent decrease in the amount of carbon dioxide in the air will lower the average temperature of the earth 6.9 degrees Fahrenheit.
We can be reasonably sure that such a sharp drop in temperature would cause glaciers to spread across the earth. As the ice sheets grow, the oceans shrink; at the height of glacial periods ice sheets contain 5 to 10 per cent of the oceans' waters. The glaciers contain little carbon dioxide, however, because ice can hold very small amounts of carbonates compared to the same volume of sea water. The shrunken oceans thus accumulate an excess of carbon dioxide which they must release to the atmosphere in order to return to equilibrium. And so the cycle draws to a close: As carbon dioxide returns to the atmosphere, the earth's temperature rises and the ice melts away. The oceans fill to their former levels, reabsorb the carbon dioxide they had released, and a new glacial epoch begins.
So long as the total amount of carbon dioxide in the atmosphere-ocean system does not change, such a cycle of temperature oscillation will tend to repeat itself. The period of the complete cycle would be determined primarily by the time required for an ice sheet to form, grow to maximum size and melt away. Estimates indicate that this should take about 50,000 years, in agreement with the observed time for the cycle. Other time factors in the cycle, such as the period required for the ocean–atmosphere system to come to equilibrium after a change in its carbon dioxide concentration, are probably much shorter. The system never quite reaches equilibrium, however, because the freezing and melting of glaciers is out of phase with the fluctuation of carbon dioxide in the atmosphere. Glaciers are slow to form and slow to melt, so for thousands of years during the earth's recovery from an ice age the cold winds from melting glaciers continue to chill the earth.
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9 Comments
Add CommentOh god, get ready for a bombardment of proactive naysayers.
Reply | Report Abuse | Link to thisLets see how many ways they can shoot down the statistical data yet again presented to them by unbiased minds.
That was a pretty cool article. Not only did it give us a unique look backward it gave us a fresh look forward; and it was enjoyable reading too. I was twelve years old when that was written. The streets of my home town were dusty and just about every vehicle and smoke stack was a choker. Those things a much improved now, none the less global co2 volume increases. In fifty years this scenario may repeat its self and a reader will write things are better now but co2 volumes continue to increase.
Reply | Report Abuse | Link to thisIt is good that mankind works to clean up the environment because it makes our earth a more enjoyable place to live regardless of whether we can put off the next ice age or not.
Great summary on the subject! .A good conclusion from it may be trying to reduce the amount of fuel spent on transport by bringing down the size of cars, and that of housing and industry by using isolation and more efficient heating and cooling systems. Fusion energy is on its way and the future may be not so bad. By the way: how about the decrease in gases solubility in water when sea temperature raises? Regards
Reply | Report Abuse | Link to this"Science progresses, funeral by funeral." _ Max Planck
Reply | Report Abuse | Link to thisPlease no more CO2. Before the time CO2 really does become a problem mankind will have switched to something else, hopefully fusion. Not to save the planet which in the words of George Carlin "ISN'T GOING ANYWHERE", but because we really need the energy - hundreds and thousands of times more than we are currently using. I hope when this global warming hoax is finally totally exposed and Al Gore receives his true title of CON MAN OF THE MILLENIUM that your readers remember how willingly Scientific American promoted this HOAX. Your publication doesn't have the journalistic integrity of the National Enquirer.
Reply | Report Abuse | Link to thisCO2 can't be a green house gas on earth because it absorbs infrared radiation at wavelengths that are not radiated by the earths surface. In the article it says CO2 absorbs infrared radiation in the range 13-17 microns - this corresponds to a surface temperature of about -100 celcius to -73 celcius - there is nowhere that cold on earth. Most of the earths surface is at about 17 celcius - this radiates at about 10.5 microns, CO2 is transparent to infrared radiation at that wave length.
Reply | Report Abuse | Link to thisScience doesn't change, politics changes science. It's refreshing to see that back in 1959, studies involving CO2 and temperature were not biased by current global warming alarmists.
Reply | Report Abuse | Link to thisLet's face it, the Earth are far more supreme an one step ahead of man. Let's focus on man's detrimental impact on the environment and not global warming.
From the Wiki link about John Tyndall:
Reply | Report Abuse | Link to this"He was the first to correctly measure the infrared absorptive powers of the gases nitrogen, oxygen, water vapour, carbon dioxide, ozone, methane, etc.
He concluded that water vapour is the strongest absorber of radiant heat in the atmosphere and is the principal gas controlling air temperature.
Absorption by the bulk of the other gases is negligible.
Prior to Tyndall it was widely surmised that the Earth's atmosphere has a Greenhouse Effect, but he was first to prove it.
The proof was that water vapor strongly absorbed infrared radiation."
Now - how are they going to tax water vapor?
First, John Tyndall stated that water vapor was the main gas blocking photons from escaping into space. CO2 was in the "bulk of the other gases" with negligible absorption. Thus, CO2 has a negligible effect on global warming.
Reply | Report Abuse | Link to thisSecond, notice that CO2 blocks all 15-micron photons. This means that more CO2 cannot block more photons since they are all blocked already.
Third, we should not forget that photons in sunlight at 15-microns are also blocked, thus cooling the Earth's surface in the daytime.