Cool Stuff (Part II)
by Alec McCarter March 2003
There is now good evidence that changes in the Earth’s climate have been regularly recurring events for millions of years. Relatively short periods (approximately 20,000 years) of warming have preceded long, sustained cooling (about 80,000 years) during which thick ice sheets covered extensive areas of the world. Each glaciation was ended, or interrupted by warming and melting of ice. In the Antarctic ice sheets have persisted, despite advances and retreats, for at least 35 million years, whereas in North America, after being present for nearly two million years, most of the ice melted.
There is no evidence of human intervention in the early cycles. It is unlikely that there could have been any because the sedimentary rock which provided the data on climate change was nearly 25 million years old, whereas the oldest fossil of human-ancestral origin, associated with the use of stone tools, is ‘Lucy’s’ jaw. Lucy, a primitive being by all accounts, lived only 2.33 ± .07 million years ago.
Imagine the world under ice. So much of the Earth’s water was in the frozen form that the atmosphere became very arid. Forests burned or died and were destroyed by ice. The entire planet cooled. Areas not covered with ice became grasslands and deserts took their place. The oceans decreased in volume, cooled and became saltier and more dense. Ice advanced until it got to warmer regions where it could not last throughout the year. Ocean currents must have changed, and, along with that, the levels of nutrients in the oceans changed too. There is really no doubt that the biological consequences of these changes were enormous for all living creatures, and will be devastating again if those events should be repeated. Massive extinctions of plants and animals took place, but among them, some, able to cope with the changed climate, developed and thrived. After the retreat of the ice, forests followed, but they were comprised of a succession of different species. It is evident that resilient Life recovered, but it was changed. Adaptation to changed circumstances is part of Life’s nature but individuals and even whole species may be dispensable as the price of change.
As the ice melted, bare ground and water took its place, reflecting less energy back into space. Thus, the Earth warmed. Once the ice retreated, much more energy was available for warming. Eighty times as much energy is needed to convert ice to water at the melting point as is needed to warm the same mass of water by one-degree Celsius. Was this bit of physics involved when, after the ice sheets melted, the rate of heating of the atmosphere and oceans increased so rapidly? Recently discovered are deposits of solidified methane at the bottom of the oceans, stable if it remains below about 300 meters. The evidence suggests that throughout millions of years, each new cycle of warming was accompanied by an increase in atmospheric carbon dioxide and methane, with a concomitant rise in atmospheric temperature. Did the decrease in depth of the oceans at the end of each period of glaciation allow methane to be released into the air? The same thing would be expected to happen if the temperature of the oceans were to increase.
It is one thing to observe from the examination of factual data, what trends may derive from them; it is quite another to assign a cause, or causes for the trend. Specifically, when events are linked, as they are in these studies, it is difficult to separate cause from effect, and particularly difficult when the time-scale is so enormous. Did rises in temperature cause increased production of greenhouse gases, or was it the other way around? Or both? What was the source of these greenhouse gases long before Man vacated caves and had not yet become an inhabitant of North America?
No matter where one starts to look at the interactions of physical and biological processes, one soon finds that the complexity is almost overwhelming. In a very real sense, the Earth has characteristics of a biological organism, though a very complex one. It is capable of responding or adapting to stresses put upon it so as to reduce the stress.
Even in our little pond at the foot of the rock, fertilizer causes a bloom of algae (phytoplankton), followed by die off and subsequent clearing of the water. The same thing happens in the Atlantic Ocean every year, on a massive scale.
Cold seawater at the Antarctic and Atlantic poles dissolves huge amounts of carbon dioxide from the air which are then carried slowly around the world by deep ocean currents. This water at a temperature close to 00C is in contact with the ocean’s bottom to which the detritus of sea-life falls, looking very much like flakes of snow from the sky. The cold water becomes enriched with nutrients. Trapped below the layer of warm water above, it might travel thousands of miles before something causes an upwelling of nutrient-rich water to occur from the deep into the sunlit waters above. This triggers a massive growth of phytoplankton thus sequestering massive amounts of carbon in living cells which in turn, are food for other creatures who also increase greatly in numbers. A host of these, (Foraminfera), have shells made of calcium carbonate. The white cliffs of Dover, part of the enormous deposits of chalk in southern England, are composed of the skeletons of such creatures. A great chain is set in motion, but eventually slows as nutrients are reduced to very low levels. The plants and animals, deprived of food, die and rot by microbial action. Carbon dioxide and methane are produced.
Methane in solid form as a hydrate, has been found in ocean sediments and is distributed so widely in such quantities that they are estimated to be about double the amounts of carbon in all coal, oil and gas deposits in the rest of the world. The School of Earth and Ocean Sciences at the University of Victoria is making important contributions to the study of methane hydrates in the ocean.
It is a theory, not yet generally accepted, that natural hydrocarbons are not necessarily derived from fossil vegetative matter. Recent laboratory studies suggest that methane and crude oil might be made continually deep in the earth’s crust where high temperatures and great pressure exist. Interestingly, the raw materials for this synthesis of hydrocarbons are calcium carbonate to provide the carbon, water, to provide hydrogen and iron oxide as a catalyst.. These raw materials are available in immense quantities. This new information suggests that there is still a great deal to be learned about the carbon cycle and its regulation. Who would have thought of solid methane hydrates at the bottom of the ocean?
Set in motion by cyclical cosmic events, these chemical and biological consequences are cyclical too, and operating on a very long time-scale. Life in its great diversity does not exist in a state of equilibrium, stable and unchanging—rather it is subject to overshoots past the state of equilibrium: like a pendulum, it swings from food and the fed to the fed and the dead. If it appears otherwise, it is because we are looking at too short a time interval to be able to see and understand the grand scheme. Ten years, or even a hundred are but moments on the scale of a hundred thousand years.
The majestic sweep of these great events occurring through thousands and millions of years, over and over again should reveal to us human beings how puny are our efforts in comparison with those of our Universe and our world. It is fear that drives us now to think that, for the first time in history, we can manipulate our world’s climate, but perhaps, this time....? And it’s partly arrogance too, just as it is arrogant of me to think that I might grasp enough of this subject to write about it.
There. That will have to do for today. The sun is setting and it’s getting chilly. I’d better go in for supper. What started this dreaming?
Ah, yes. The rock. There it is. Silent. What a lot it could tell us — but it knows even less of the future than we do.
Cool stuff II has been reprinted from the Finnerty Gardens Newsletter