Is Global Warming Human Induced or is it a Natural Phenomenon?
The term Global Warming refers to the observation that the atmosphere near the Earth’s surface is warming. In recent times there has been a surge in the awareness about global warming. The causes of global warming are the subject of extensive research around the world and scientists have come up with a significant amount of evidence showing that the earth’s temperature is rising at a constant rate. In last century alone the temperature has increased by more than CFC. This warming has been particularly strong during the last 20 years and has brought along retreating glaciers, thinning arctic ice, rising sea levels, lengthening of growing seasons, and earlier arrival of migratory birds. The issue of global warming concerns us all and the effects of global warming can have are far too much risk to be ignored.1
Even though a lot of evidence points towards the fact that global warming is taking place, a considerable number of people still dismiss this idea. The question of whether global warming is actually taking place is another issue which comes up and I will not go into the details of this question. In this essay I will simply assume that global warming is taking place. Firstly, because all the research points towards that way and secondly, there is general view to believe it global warming is taking place.
In this essay I will try to address the question of whether global warming is human induced or whether it is just a natural phenomenon. To start with, the question is already difficult to answer. It becomes even more difficult as most of the information we have is blurred. The problem is different scientists, governments and environmental protection groups all have different viewpoints. The scientific evidence we have collected about temperature change and the concentration of greenhouse gases can be interpreted in two different ways: One way pointing to human interference in the environment and the other to natural occurrence. This issue has been the subject of many debates, arguments, and now the focus of this essay. From the sources available, I gathered the facts which give the most clear and precise information. The evidence for both sides of the argument is taken from studies and research done by governmental institutions and universities.
I will start by explaining how global warming takes place. Scientists disagree on how exactly global warming takes place, but the most widely held belief is the greenhouse effect theory. Certain gases in the atmosphere act like the glass in a greenhouse, allowing sunlight through to heat the earth’s surface but trapping the heat from radiating back into space. As the greenhouse gases build up, the atmosphere of the earth gets hotter. The main greenhouse gases are water vapour, carbon dioxide (CO2), methane, chlorofluorocarbons (CFCs) and nitrous oxide (N2O).2
Let me move on and look at the evidence and arguments for global warming being human induced. There is strong evidence from studies done by various research organizations. The National Science Foundation3 for example reconstructed global temperature over the past 600 years and determined that the 1990s was by far the warmest decade and the average temperature in 1997, 1995 and 1990 were extremely alarming. The study also found that the levels of carbon dioxide went up by 25% during the last century. The scientists also studied “natural forcings”, that is, factors that can affect climate significantly but which are not part of the climate system itself. Based on statistical comparisons and analysis, they have found that natural changes in the brightness of the sun and volcanic emissions both played an important role in governing climate variations.4
National Oceanic and Atmospheric Administration5, this time studying the temperature in the oceans, reported that heat in the deep ocean had been increasing at a surprising rate and that it contained far more heat energy than previously thought. According to the lead scientist, Sydney Levitus, “The data filled a missing piece of the global warming puzzle, suddenly scientists realized that the deep ocean was a heat-sink of sorts, and that the ocean was the place where much of the predicted heat of global warming was stored.” The data they got from the deep ocean was fed into two of the world’s most sophisticated computer generated climate models. The results they got back are evidence that human activity is partly responsible for current climate warming. Both models strongly suggest that the extra heat in the oceans can’t be explained by natural variability6.
Another piece of key evidence, to support human induced climate changes, come from scientists comparing the temperatures in the southern and northern hemispheres, where most of the human activity such as burning fossil fuels and cutting down forests, with the southern hemisphere. The study is based on the fact “…that past values for temperature in the southern hemisphere help us predict temperature in the northern hemisphere better than just looking at past values for temperature in the northern hemisphere,” says Kaufmann7. Temperature in the northern hemisphere is in a statistical sense dependent on temperature in the southern hemisphere, but the reverse, however, is not true because of the weather patterns seem to work this way. So using these facts and analysing records of temperature in southern and northern hemisphere, from 1865 to 1999, the scientists have determined that there have been variations in the climate patterns which cannot be explained by natural occurrence. The changes, according to the scientists, can only have taken place due to human activities such as deforestation, burning oil, natural gas, and coal, emitting chlorofluorocarbons and various other activities which release greenhouse gases8.
The cornerstone of the argument for human-induced global warming is the climate models generated by supercomputers. These models are generally called “general circulation models” and their purpose is to simulate many features of the climate. Many of the environmental groups along with their experts claim that these models, which are manually programmed by humans, can give us a reasonably accurate prediction of what the temperature and climate will look like in the future. Most importantly, they claim that the computers are programmed to ignore natural interference, thus showing changes in temperature only due to human activity9.
There is significant evidence to support the argument put forward by the people who think that global warming is fully, if not, mostly human induced. The other side think otherwise and although they are in the minority they still have a pretty good case. Now I want to look at the arguments from the people who think global warming is fully, if not, mostly natural. Firstly, many of the leading scientists believe that the gases we are emitting are not enough to cause climate change. According to a report published by the Intergovernmental Panel on Climate Change (IPCC)10 90 billion tons of carbon dioxide annually circulates between the earth’s ocean and the atmosphere, and another 60 billion tons exchange between the vegetation and the atmosphere. We can compare this data to the man-made emissions which added up to about 5 to 6 billion tons per year, the natural sources would then account for more than 95 percent of all atmospheric carbon dioxide11.
According to professor of geography, Robert Essenhigh, “At 6 billion tons, humans are then responsible for a comparatively small amount, less than 5 percent, of atmospheric carbon dioxide,” he said. “And if nature is the source of the rest of the carbon dioxide, then it is difficult to see that man-made carbon dioxide can be driving the rising temperatures. In fact, I don’t believe it does.” 12 Some scientists believe that the human contribution to carbon dioxide in the atmosphere, however small, can upset the earth’s environmental balance. Essenhigh has proved that, mathematically, the hypothesis is inadequate and lacks evidence to support the theory13.
Another study done by Cambridge University geology department has found that global temperature has been oscillating (going up and down) steadily, with an average rising gradually over the last one million years, long before any human industry began to release carbon dioxide into the atmosphere. The study also showed that during the last 100,000 years, the temperature rose more significantly than it had done before. The explanation put forward points out that, today we have reached near peak in the current cycle that started about a million years ago. Some scientists predict that the global warming will reach its peak by the next 10 to 20 years and then the earth will supposedly cool down, starting a new ice age14.
One of the key areas of debate is do with the climate models, with many researchers question the validity of the predictions given by the computer generated models. The programmers themselves admit that the climate models are in fact too complicated and are not accurate enough to provide reliable forecasts of how the climate may change and several models often produce contradictory results. They only use these climate models because for the time being all they have are these to predict future climate changes15. Professor Collin Millard says, “The global general circulation models which simulate significant amounts of human-induced warming are incorrectly structured to give this positive feedback loop. Their internal model assumptions are thus not realistic.” 16
William Grey, a correspondent and researcher, along with his team of researchers have worked for more than 10 years to investigate natural forces which affect our climate. They examined countless reports, studies and statistical data. They have come to the conclusion that the subject of global warming has been “…extended and grossly exaggerated and misused by those wishing to make gain from the exploitation of ignorance on this subject.”17 They also mention that the governments of developed countries, the media and scientists who are willing to bend their objectivity to obtain government grants for research on this topic are all to blame18.
That’s all the information I have decided to use and a closer look reveals gaps in substantiating the evidence. The research taking place today has not reached the stage where we can be a hundred percent certain about the results. Even though this essay assumes that global warming is taking place, the question of whether global warming is taking place is still a valid one. There is evidence from NASA scientist John Christy to maintain this argument. While compiling satellite data extending back to 1979 (which is not very long, in global terms), Christy found that temperature measurements in the Earth’s upper atmosphere showed a cooling of two degrees Fahrenheit over the past two decades. Because most scientists, who specialize in this field, have presumed that global warming would affect all layers of the atmosphere in a uniform way, Christy’s research has been a foundation of the arguments for those who disagree with reports on the severity or even the existence of global warming19.
Before I can come to a solid concluding argument, we must evaluate the evidence. As I mentioned, there are gaps and doubts in the evidence. This means it is very hard to make accurate judgments and predictions. I want to first of all analyze the evidence from the point of view of the people who think global warming is human induced; much of the evidence comes from the computer generated climate models. Even if these models are not fully accurate, virtually all the published predictions about climate change are based on the results from these models. We have to assume that there is some basis of evidence in these models or these climate models would have been discarded a long time ago. The numerous studies and reports are also equally reliable, even if most of the studies fail to take into account the natural climate cycle and tend to concentrate only on the increases in greenhouse gases; they prove to have some truth nonetheless.
Meanwhile, the arguments to support global warming is being natural, for the most part is based on dismissing the arguments and evidence from the other side. Looking at the history of earth, the facts show that there have been several ice ages and years of extreme heat. What the earth is experiencing now could be just another one of these natural cycles.
The majority of the people, simply just accept the idea that global warming is human induced. I personally started writing this essay thinking there was no doubt humans were solely responsible for global warming, but now almost at the end of it having second thoughts. I must admit the evidence I found for global warming being natural is quite strong and possibly even better than the other side. This question is particularly difficult to answer because there seems to be a lot of circumstantial evidence and there needs to be a lot of research done into this field. For the time being we must take whatever steps necessary to reduce the impact of global warming. The impacts are another important question to consider; unfortunately this essay will not answer that question.
So the big question is whether global warming human induced or is it a natural phenomenon? Well, there is significant evidence and strong arguments from both sides. It is hard to single out only one cause for global warming. During the past 100 years the temperature has increased so much that it would never be possible for just natural forces to cause the increase. So the truth is, the temperature is rising naturally and it would have done so with or without human interference. The temperature increases, however, would have been at a lot slower rate, but because of human interference the rate of temperature increase is a lot higher. The conclusion I have come to is that both human activities and natural forces are responsible for global warming. The only question now is which of the two is more influential in bringing about global warming, that is if they are not equally responsible.
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Gray, William. “Viewpoint: Get off warming bandwagon.” BBC website (16 November, 2000). <http://news.bbc.co.uk/1/hi/in_depth/sci_tech/2000/climate_change/1013434.stm> [18 april 2003]
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< http://yosemite.epa.gov/oar/globalwarming.nsf/content/index.html> [24 April, 2003]
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