Friday, March 4, 2011
Examining Alternative Theories
There are a variety of alternative theories put forth by the skeptics in this camp. Sunspots and sun cycles have been blamed for global warming, as have volcanic eruptions, cosmic rays, and various other astronomical causes (variations in Earth's axial tilt, the fluctuating eccentricity of Earth's orbit and the precession of equinoxes as relates to perihelion and aphelion, for instance). Now, there is no question that these various factors do affect Earth's climate, and that can be seen clearly in the record of ancient climates. We know that the Earth has seen periods of natural warming and cooling, and there is no doubt that these sorts of changes will happen again. Nevertheless, these variables cannot explain the warming trend over the last 100 years or so nearly as well as anthropogenic factors, like the emission of enormous levels of carbon dioxide corresponding to the industrial revolution.
Skeptics of mainstream climate change theory may take to these other hypotheses in part because there is a sense that we humans are not capable of making big changes in our ecosystem. Of course, history tells us otherwise. Human beings have driven many species to extinction or to the brink of extinction by over-hunting and habitat destruction, and in the 20th century, with the advent of chlorofluorocarbons (CFCs), we put an enormous hole in our ozone layer. Meanwhile, we continue to possess the power to cause a global nuclear winter.
To understand how humans are capable of making such profound changes to the climate, we have to understand the two main elements behind our increased impact on the environment: the industrial revolution and recent population expansion.
Beginning in the 1700s and increasing throughout the next few hundred years, the industrial revolution was responsible for an unprecedented level of fossil fuel burning and deforestation. The natural carbon cycle of the Earth, whereby carbon dioxide is emitted by natural processes like respiration and absorbed by natural processes like photosynthesis, was upset for the first time by the artificial emission of CO2. There is no natural process on the Earth that is capable of taking the carbon trapped deep below the surface and spewing it into the atmosphere at the rate of human capacity. Second, coinciding with the industrial revolution was the staggering growth of the human population. Since 1800, it is estimated that the human population has grown from about 1 billion people to almost 7 billion people. For almost the entire history of humanity the population was under 1 billion, but just in the last two hundred years we have increased our numbers 600%. That's a lot of people, and each one of us is responsible for contributing a small portion of the world's CO2 output, natural and artificial. But just think of how many cars, trucks, trains, planes, ships and power plants there are involved with sustaining such an enormous population, and think of how much exhaust these machines dump into the air in a single year.
But of course, we're not just dealing with the carbon emissions of a single year. As the balance of CO2 emission and absorption is upset, more carbon dioxide is retained in the atmosphere, and over time this builds up. It's a bit like an overwhelmed bilge pump on a ship. Even if the pump continues to function at full power, the ship will eventually sink if the water comes in faster than it can be removed. Similarly, we are dealing with all of the excess CO2 built up since the beginning of the imbalance, so we're really facing the combined force of many years' worth of excess carbon. There is some uncertainty as to how long the carbon dioxide will remain in the atmosphere, but there is no question that the system is saturated. And by the way, we haven't stopped the activities that are causing the problem.
We know how greenhouses work. We have put them to use growing tropical plants in the winter months. But of course, our atmosphere is not made of glass, but of various gases. Carbon dioxide is one constituent of the atmosphere, and it is considered a greenhouse gas. A little bit is a good thing: the greenhouse effect is responsible for keeping the Earth warm, by trapping some of the Sun's radiation in our atmosphere. But if we are to increase the level of greenhouse gases in the air, more heat is trapped. This is just basic chemistry and physics. There can be no doubt that the greenhouse effect is responsible for keeping the Sun's heat inside, and there should be no doubt that altering the chemistry of our atmosphere will alter the behavior of the system.
What is so mystifying about the alternative global warming theories is that they are comparatively far-fetched. Just think about it. Is it more likely that the well-documented increase in global temperatures is related to the well-documented increase in greenhouse gases in the atmosphere, which correlates well to the increase in fossil fuel burning and human population growth? Or is it more likely that a number of other factors, which have historically caused changes to the Earth's climate on the scale of thousands of years, have suddenly cropped up inconveniently to raise global temperatures at a drastic rate? It is not enough simply to say that the Earth has experienced natural climate changes before, and therefore the changes we're seeing now are natural. Climate change doesn't just happen on its own, there must be some kind of forcing, and while the correlation between CO2 and temperature increase is clear, the data on other proposed factors (solar activity and cosmic rays, for example) shows no such correlation. The choice is between a theory that hinges on a straightforward mechanism with straightforward results, and a theory that relies on coincidences, uncertainty, and unpredicted phenomena. Tellingly, there is no consistent hypothesis among the climate change skeptics. A brief search on the internet will yield an abundance of alternative explanations, but there is a reason no single idea is embraced by all the opponents of the mainstream theory: none of the rebuttals are iron-clad, and most try to isolate one aspect of the evidence for global warming and tear it apart, utterly ignoring the fact that there are several independent lines of evidence that corroborate each other in support of anthropogenic climate change.
But this begs a larger question: why have opponents of mainstream climate change theory been so desperate to latch on to alternative theories? What is it about the carbon emissions hypothesis that they find so unacceptable? Is their opposition strictly based on its economic implications? Considering the issue's partisan divide, it's difficult not to conclude that the politicians on the right have criticized mainstream climate science, not so much because of flawed evidence, but because of the problems it causes for their corporate contributors. Combine this with a powerful public relations campaign on the part of oil companies, and fears in the Rust Belt of a collapse in coal demand, and we can start to understand how the truth can be obscured. There is much interest in maintaining the status quo.
We may feel sympathetic for those working class folks whose jobs are threatened by the transition to a clean energy economy. But if that is the case, we as a nation should invest in jump-starting the transition process, and making sure these hardworking Americans are trained to work in the new energy sector. No one wants to deprive these people of a job, and it's certainly not their fault that we need to give up our dependence on fossil fuels. But we also cannot continue to destroy the planet because there are jobs at stake. It will be up to the politicians to help ease the transition. And as for the overall economic impact of a clean energy revolution, it should be a net positive. The sooner we embrace reality, the sooner we can get working on making sure the United States is on the cutting edge of low-cost, high-efficiency products. As the world makes the transition to clean, renewable energy, they'll need the technology, and we should be ready to sell it.
To be clear, the Earth itself is not in great danger. The Earth is resilient, and it has seen substantial changes to its climate over the ages. We are not yet close to effecting such change. But if the rate of warming in our time is very fast, other species may not be able to adapt. Some kinds of life will survive these changes, but we may be responsible for the end of many hereditary lines in the biological world. Even so, new species will take their place. Life goes on. But we are also threatening the climate to which we humans are accustomed, and we are flirting with a global catastrophe with severe consequences for the future of humanity. Considering how much difficulty we have with sporadic flooding, droughts, powerful hurricanes, and mass population displacements, it's apparent that we are nowhere near ready to deal with these events on a larger scale. We must think seriously about our preparedness for such an eventuality, and we should ponder the tragedy of premature extinction.
It should be noted that skepticism is a very important part of the scientific endeavor. Skepticism has liberated us from mystical explanations for natural phenomena, and it helps us avoid taking assertions at face value. It is essential the we interrogate the world around us with an open mind, and it does us no good to swallow climate science, or any other science, as fact, without investigating it more deeply. It is crucial that any finding be tested and confirmed by other scientists. But that has already occurred. Global warming has been predicted and tested by science for more than 100 years. It is true that some of the most important scientific findings of ages past have challenged the conventional wisdom; the controversial heliocentric model of the universe advanced by Nicolaus Copernicus comes to mind. But not every scientific finding is erroneous, and not every fringe scientist is Copernicus. We must always be open to having our minds changed, but extraordinary claims require extraordinary evidence.