1. Runaway greenhouse effect
Earth, Mars and Venus share certain broad similarities as planets and yet their general climates are very different from each other. Venus has a surface temperature that can melt many metals, Mars is unbearably cold, while the planet earth enjoys a temperature that is just right for life. What accounts for such stark differences The answer is simple, it is the presence of the atmosphere and a particular phenomenon related to it known as the greenhouse effect that have caused the three terrestrial planets of the solar system to take completely different routes in their evolution.
Planetary bodies that are adequately dense and big in size have gravities strong enough to trap any gases that may ooze out of their depths to escape into space, thereby developing a layer of atmosphere. When the sunlight of visible spectrum impinges on a planet, much of it is reflected back. However, the reflected light is of longer wavelength and is categorized as infrared radiation. Though the atmosphere could be transparent to visible light, it tends to absorb infrared radiation. Certain gases that could usually be present in the atmospheres of earth-like planets absorb the reflected radiation because of their molecular structures (Nash, 2008). This phenomenon of trapping of solar energy is called greenhouse effect, and the so-called greenhouse gases, water vapor, carbon dioxide, methane, etc, are responsible for this. These gases increase the temperature of a planets atmosphere and make the planet hotter than it should otherwise be.
Sometimes, as in the case of the planet Venus, a positive feedback mechanism develops in the greenhouse effect of the planet, driving the temperatures far out of the normal range. This happens when large amounts of gases that were trapped in the surface layer or that may exist in liquid or solid form on the surface of a planet begin to be slowly released into the atmosphere due to an increase in temperature that could be explained by the normal greenhouse effect or some other cause. The addition of these greenhouse gases in the atmosphere increases the temperature of the planet, which in turn forces the release of more greenhouse gases, which further increase the temperature. The loop continues till all the greenhouse gases on the surface of the planet are released into the atmosphere, by which time the planet could have become a boiling furnace. This kind of runaway greenhouse effect happened on Venus, it could happen on the earth in future.
2. Climatic history of Venus and Mars
During the heyday of science fiction in 1940s and 50s, writers thought that Venus could be an exotic planet covered with lush vegetation. They imagined that in the future people from earth would go to Venus on holiday safaris. These fantasies were dashed, however, when Soviet probes to Venus in the 1960s painted a picture of a living inferno. Venus has a surface temperature of about 460C (860F). Its atmospheric pressure is 92 times greater than that of the earth. To explain these extreme temperature and pressure conditions, scientists hypothesized that billions of years ago, Venus and Earth shared similar climatic conditions with abundant presence of liquid water however, Venus was subsequently subjected to a runaway greenhouse effect. To begin with, the basis difference between earth and Venus is that Venus is much closer to sun than earth. The original higher temperatures of Venus were able to cause a positive feedback to loop to set in.
Billions of years ago, the sun was much cooler than it is now. As the suns temperature increased, Venus water seas increasingly evaporated. Thus, though the suns heat stabilized after a time, Venus temperature went on increasing because of the increased water vapor in the atmosphere which evaporated more water into water vapor which absorbed more reflected radiation and increased the temperature of the planet and evaporated more water. This led to a point where oceans simply boiled away. Venus also had great reserves of carbon dioxide locked up in its rocks, just in the way earth has today. As the temperature of the planet kept rising due to water vapor feedback loop, the carbon dioxide slowly began to be released from the crust and supported the positive feedback loop. The rising temperatures of Venus went much beyond 100C because even after the oceans were melted, the carbon dioxide loop continued for much longer. Today, 96 of Venus atmosphere is made up of carbon dioxide (as contrasted to less than 4 of CO2 in earths atmosphere), but there is little water vapor left. This is because when water vapor rises sufficiently high in a hot atmosphere like that of Venus, it is exposed to ultraviolet radiation which splits H2O into hydrogen and oxygen gases, and then hydrogen would escape into space while oxygen would combine with other gases present in the atmosphere (Strobel, 2007).
The atmosphere of Venus continues to be studied the space probe Venus Climate Orbiter that is due to be launched later this year is expected to provide us more clues regarding the planets atmosphere and climate.
Mars is of course a favorite destination not only for SF authors but also for many scientists and enthusiasts, and not only for holiday purposes but also for permanent living and working. Decades ago scientists thought Mars had a very similar atmosphere and climate to ours, and although such imaginings were proven to be grossly optimistic, people continue to dream about Mars. Mars did not undergo a runaway greenhouse effect like Venus did, nor does it have a moderately warm temperature like Earth has. Mars surface temperature could go as low as minus 87C during the winter, although in summer it could be tolerably balmy. Mars has a wide range of temperature because it does not have a thick atmosphere like earth has, and consequently its temperatures are not moderated. The atmospheric pressure density of Mars is only 1 that of the earth.
Mars too could have started like earth in terms of its atmosphere, climate and some other important planetary features. Earth has a huge magnetic layer around it stretching for thousands of kilometers into the outer space. This magnetic layer is generated by a rotating mass of molten iron at earths core. In the case of Mars, such a planetary dynamo somehow ceased to function very early on in the planets history, as a result of which it could not retain its magnetosphere. The stripping of Mars magnetosphere exposed the upper layers of its atmosphere to the radiation of the solar wind. Moreover, Mars is much smaller in size than earth, with a surface gravity of about 38 as that of the earth. Mars lesser gravity too did not help it retain its atmosphere.
Ironically, Mars too has about 95 carbon dioxide in its atmosphere, just like Venus. But this carbon dioxide is not effective in generating any significant greenhouse effect because it amounts to very little in actual mass or volume. Only a minor greenhouse effect is created (Miles, 2008). Nevertheless, Mars future could be very much tied up with the greenhouse effect. People of earth have great designs on Mars. The age of Mars exploration is just about to begin. If we are ever going to colonize the planet on a mass scale, we would have to subject the planet to a stupendous process called terraforming which aims at making Mars more earth-like. Terraforming of Mars could take at least a hundred years, and it initially involves releasing large amounts of greenhouse gases into the Martian atmosphere artificially so as to try to increase the temperature of the planet and make its atmosphere thicker, despite the lack of a magnetosphere to protect it (Bonsor, 2010). If any positive feedback loop develops in the effort of terraforming Mars by releasing greenhouse gases, it could spare a great amount of effort for people working on the project.
3. Greenhouse effect on Earth
In itself, the greenhouse effect has been a very beneficial process on earth, without which life could not have probably evolved on this planet. Earth has a remarkably moderate and stable climate that is just suitable for the flourishing of life on this planet. Nonetheless, in its billions of years of geological history, the planet has seen considerable fluctuations in its climate, presenting hostile climatic conditions to many of its inhabitants for long stretches of time.
Earth has seen many extinction events in its long history, but the greatest of them was the Permian-Triassic extinction event that happened 251 million years ago when over 80 of the living species perished. One of the major hypotheses advanced to explain this catastrophe was a runaway greenhouse effect caused by increased volcanism and or abrupt release of methane hydrates from the ocean floor, methane being a powerful greenhouse gas. Though such extreme climatic events were rare, warming and cooling cycles keep recurring on the planet. For example, there have been many long spells of ice ages in the past, and these deep freezes will continue occurring on the planet in future.
In the past few decades, the average temperature of the earth has risen by about 1C. Such fluctuations in earths temperature have not been uncommon in the historical continuum of the human civilization itself. If the current global warming is happening in the natural course of things, we can expect it to stabilize or even if it does not there is not much we can do to counteract it. However, since the advent of Industrial Revolution 200 years ago, humanity has become excessively dependent on fossil fuels the burning of fossil fuels releases carbon dioxide into the atmosphere and it is widely believed in our times that the ongoing global warming is anthropogenic, induced by the CO2 pollution caused by human activities. This is the majority view today, although there continue to be a large number of scientists and experts who contest the claim (Michaels, 2005). The fact is that water vapor is present in our atmosphere in vastly greater quantities than carbon dioxide, and the actual levels of carbon dioxide in the atmosphere have only increased by an apparently insignificant percentage in the last 50 years or so.
It would seem logical to conclude that 200 years of heavy pollution man has created could have begun to dramatically affect the global climatic system at the same time, it could also be that the global climatic system is highly resilient and the earths atmosphere as a whole may be too vast to be impacted by the side effects of human activities, notwithstanding the obvious and undeniable harm caused by pollution at a local level. Whether caused by humans or not, global warming is inherently a very dangerous phenomenon that is always likely to start a positive feedback loop that can go out of control.
4. Human response to global warming
Much more scientific evidence need to be gathered and many more studies conducted to determine the exact nature and extent of the current global warming. A great problem in the current trends about the debate about global warming is that they are only too often influenced by politics, economics and preconceived notions. In this matter, amazingly, even scientists who are supposed to study and express their findings objectively have become prone to prejudice. This tendency has to be dramatically curtailed if the public are to be informed about the truth of global warming on a purely scientific basis.
Meanwhile, we cannot wait for scientists to come out with a total consensus any time in the near future, because the nature of the subject is vast and complicated in itself. If the current global warming proves to be caused by humans, it may be too late to act at a future time. The time to act is now, and one of the most effective ways to deal with this crisis is to replace our fossil fuel as early as possible. Massive amounts of research needs to be conducted on the viability of alternative fuels, especially algae biofuels. Whether or not global warming is happening because of human doings, replacing fossil fuels entirely in the next ten years will get us rid of pollution, and make our cities cooler by annulling the temperature rise caused by the blankets of smog that cling around them.
Earth, Mars and Venus share certain broad similarities as planets and yet their general climates are very different from each other. Venus has a surface temperature that can melt many metals, Mars is unbearably cold, while the planet earth enjoys a temperature that is just right for life. What accounts for such stark differences The answer is simple, it is the presence of the atmosphere and a particular phenomenon related to it known as the greenhouse effect that have caused the three terrestrial planets of the solar system to take completely different routes in their evolution.
Planetary bodies that are adequately dense and big in size have gravities strong enough to trap any gases that may ooze out of their depths to escape into space, thereby developing a layer of atmosphere. When the sunlight of visible spectrum impinges on a planet, much of it is reflected back. However, the reflected light is of longer wavelength and is categorized as infrared radiation. Though the atmosphere could be transparent to visible light, it tends to absorb infrared radiation. Certain gases that could usually be present in the atmospheres of earth-like planets absorb the reflected radiation because of their molecular structures (Nash, 2008). This phenomenon of trapping of solar energy is called greenhouse effect, and the so-called greenhouse gases, water vapor, carbon dioxide, methane, etc, are responsible for this. These gases increase the temperature of a planets atmosphere and make the planet hotter than it should otherwise be.
Sometimes, as in the case of the planet Venus, a positive feedback mechanism develops in the greenhouse effect of the planet, driving the temperatures far out of the normal range. This happens when large amounts of gases that were trapped in the surface layer or that may exist in liquid or solid form on the surface of a planet begin to be slowly released into the atmosphere due to an increase in temperature that could be explained by the normal greenhouse effect or some other cause. The addition of these greenhouse gases in the atmosphere increases the temperature of the planet, which in turn forces the release of more greenhouse gases, which further increase the temperature. The loop continues till all the greenhouse gases on the surface of the planet are released into the atmosphere, by which time the planet could have become a boiling furnace. This kind of runaway greenhouse effect happened on Venus, it could happen on the earth in future.
2. Climatic history of Venus and Mars
During the heyday of science fiction in 1940s and 50s, writers thought that Venus could be an exotic planet covered with lush vegetation. They imagined that in the future people from earth would go to Venus on holiday safaris. These fantasies were dashed, however, when Soviet probes to Venus in the 1960s painted a picture of a living inferno. Venus has a surface temperature of about 460C (860F). Its atmospheric pressure is 92 times greater than that of the earth. To explain these extreme temperature and pressure conditions, scientists hypothesized that billions of years ago, Venus and Earth shared similar climatic conditions with abundant presence of liquid water however, Venus was subsequently subjected to a runaway greenhouse effect. To begin with, the basis difference between earth and Venus is that Venus is much closer to sun than earth. The original higher temperatures of Venus were able to cause a positive feedback to loop to set in.
Billions of years ago, the sun was much cooler than it is now. As the suns temperature increased, Venus water seas increasingly evaporated. Thus, though the suns heat stabilized after a time, Venus temperature went on increasing because of the increased water vapor in the atmosphere which evaporated more water into water vapor which absorbed more reflected radiation and increased the temperature of the planet and evaporated more water. This led to a point where oceans simply boiled away. Venus also had great reserves of carbon dioxide locked up in its rocks, just in the way earth has today. As the temperature of the planet kept rising due to water vapor feedback loop, the carbon dioxide slowly began to be released from the crust and supported the positive feedback loop. The rising temperatures of Venus went much beyond 100C because even after the oceans were melted, the carbon dioxide loop continued for much longer. Today, 96 of Venus atmosphere is made up of carbon dioxide (as contrasted to less than 4 of CO2 in earths atmosphere), but there is little water vapor left. This is because when water vapor rises sufficiently high in a hot atmosphere like that of Venus, it is exposed to ultraviolet radiation which splits H2O into hydrogen and oxygen gases, and then hydrogen would escape into space while oxygen would combine with other gases present in the atmosphere (Strobel, 2007).
The atmosphere of Venus continues to be studied the space probe Venus Climate Orbiter that is due to be launched later this year is expected to provide us more clues regarding the planets atmosphere and climate.
Mars is of course a favorite destination not only for SF authors but also for many scientists and enthusiasts, and not only for holiday purposes but also for permanent living and working. Decades ago scientists thought Mars had a very similar atmosphere and climate to ours, and although such imaginings were proven to be grossly optimistic, people continue to dream about Mars. Mars did not undergo a runaway greenhouse effect like Venus did, nor does it have a moderately warm temperature like Earth has. Mars surface temperature could go as low as minus 87C during the winter, although in summer it could be tolerably balmy. Mars has a wide range of temperature because it does not have a thick atmosphere like earth has, and consequently its temperatures are not moderated. The atmospheric pressure density of Mars is only 1 that of the earth.
Mars too could have started like earth in terms of its atmosphere, climate and some other important planetary features. Earth has a huge magnetic layer around it stretching for thousands of kilometers into the outer space. This magnetic layer is generated by a rotating mass of molten iron at earths core. In the case of Mars, such a planetary dynamo somehow ceased to function very early on in the planets history, as a result of which it could not retain its magnetosphere. The stripping of Mars magnetosphere exposed the upper layers of its atmosphere to the radiation of the solar wind. Moreover, Mars is much smaller in size than earth, with a surface gravity of about 38 as that of the earth. Mars lesser gravity too did not help it retain its atmosphere.
Ironically, Mars too has about 95 carbon dioxide in its atmosphere, just like Venus. But this carbon dioxide is not effective in generating any significant greenhouse effect because it amounts to very little in actual mass or volume. Only a minor greenhouse effect is created (Miles, 2008). Nevertheless, Mars future could be very much tied up with the greenhouse effect. People of earth have great designs on Mars. The age of Mars exploration is just about to begin. If we are ever going to colonize the planet on a mass scale, we would have to subject the planet to a stupendous process called terraforming which aims at making Mars more earth-like. Terraforming of Mars could take at least a hundred years, and it initially involves releasing large amounts of greenhouse gases into the Martian atmosphere artificially so as to try to increase the temperature of the planet and make its atmosphere thicker, despite the lack of a magnetosphere to protect it (Bonsor, 2010). If any positive feedback loop develops in the effort of terraforming Mars by releasing greenhouse gases, it could spare a great amount of effort for people working on the project.
3. Greenhouse effect on Earth
In itself, the greenhouse effect has been a very beneficial process on earth, without which life could not have probably evolved on this planet. Earth has a remarkably moderate and stable climate that is just suitable for the flourishing of life on this planet. Nonetheless, in its billions of years of geological history, the planet has seen considerable fluctuations in its climate, presenting hostile climatic conditions to many of its inhabitants for long stretches of time.
Earth has seen many extinction events in its long history, but the greatest of them was the Permian-Triassic extinction event that happened 251 million years ago when over 80 of the living species perished. One of the major hypotheses advanced to explain this catastrophe was a runaway greenhouse effect caused by increased volcanism and or abrupt release of methane hydrates from the ocean floor, methane being a powerful greenhouse gas. Though such extreme climatic events were rare, warming and cooling cycles keep recurring on the planet. For example, there have been many long spells of ice ages in the past, and these deep freezes will continue occurring on the planet in future.
In the past few decades, the average temperature of the earth has risen by about 1C. Such fluctuations in earths temperature have not been uncommon in the historical continuum of the human civilization itself. If the current global warming is happening in the natural course of things, we can expect it to stabilize or even if it does not there is not much we can do to counteract it. However, since the advent of Industrial Revolution 200 years ago, humanity has become excessively dependent on fossil fuels the burning of fossil fuels releases carbon dioxide into the atmosphere and it is widely believed in our times that the ongoing global warming is anthropogenic, induced by the CO2 pollution caused by human activities. This is the majority view today, although there continue to be a large number of scientists and experts who contest the claim (Michaels, 2005). The fact is that water vapor is present in our atmosphere in vastly greater quantities than carbon dioxide, and the actual levels of carbon dioxide in the atmosphere have only increased by an apparently insignificant percentage in the last 50 years or so.
It would seem logical to conclude that 200 years of heavy pollution man has created could have begun to dramatically affect the global climatic system at the same time, it could also be that the global climatic system is highly resilient and the earths atmosphere as a whole may be too vast to be impacted by the side effects of human activities, notwithstanding the obvious and undeniable harm caused by pollution at a local level. Whether caused by humans or not, global warming is inherently a very dangerous phenomenon that is always likely to start a positive feedback loop that can go out of control.
4. Human response to global warming
Much more scientific evidence need to be gathered and many more studies conducted to determine the exact nature and extent of the current global warming. A great problem in the current trends about the debate about global warming is that they are only too often influenced by politics, economics and preconceived notions. In this matter, amazingly, even scientists who are supposed to study and express their findings objectively have become prone to prejudice. This tendency has to be dramatically curtailed if the public are to be informed about the truth of global warming on a purely scientific basis.
Meanwhile, we cannot wait for scientists to come out with a total consensus any time in the near future, because the nature of the subject is vast and complicated in itself. If the current global warming proves to be caused by humans, it may be too late to act at a future time. The time to act is now, and one of the most effective ways to deal with this crisis is to replace our fossil fuel as early as possible. Massive amounts of research needs to be conducted on the viability of alternative fuels, especially algae biofuels. Whether or not global warming is happening because of human doings, replacing fossil fuels entirely in the next ten years will get us rid of pollution, and make our cities cooler by annulling the temperature rise caused by the blankets of smog that cling around them.
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