Fluent Essays

You only need to finish 10 multiple choice, but please provide correct answers.questiones in on the multiple choice document and you need to read the reading materials document reading_materials.docx multiple_choice.docx Unformatted Attachment Preview Chapter 16: Ice cores and other sediments show that large, rapid, and widespread climate changes have been common on Earth for most of the time for which we have good records, but have been absent during the critical few millennia during which agriculture and industry arose. At least some of those large changes appear to have been triggered by increased freshwater delivery to the north Atlantic. Climate jumps have been especially common when changes were occurring in important parts of the climate system, including summer sunshine in the north, carbon dioxide in the atmosphere, and ice-sheet size. The critical questions for us are: Will nature, or humans, return the climate to the “normal” condition of wild jumps rather than the “anomalous” stability that we now enjoy? And, if such a return seems likely, is there anything we can do about it? Firm answers are not available, unfortunately, and I doubt that answers will be found in the immediate future. But there is a significant possibility that greenhouse warming could trigger enough extra rain, snow, and ice-sheet melting to partially or completely shut down the north Atlantic conveyor circulation. Greenhouse climate changes thus could be larger and stranger than most people expect, including wintertime freezing around the north Atlantic. In this chapter, we will consider why the climate-change community is so much more confident of global warming than is the popular press. We will also take a short detour into economics, to see why abrupt climate changes are the most important ones, and why businesspeople and environmentalists may yet end up on the same side of the argument. Earth has an amazingly efficient recycling system. Plants capture and store sunlight by using its energy to make more of the carbon dioxide/water combinations that we know as plants. But animals, fungi, and bacteria make more of themselves by rearranging the plants they eat, or they slowly burn the plants they eat to gain the energy of the stored sunlight. Almost everything that dies is recycled within a few years of its death. The recycling is not perfect, however, and a few dead things escape recycling for a while, “leaking” out of the usual cycles. Where plant decay is slow (as in cold tundra regions) or where the supply of dead plants is very large (as beneath regions of ocean upwelling, where nutrients from the deep ocean fertilize blooms of plankton), dead plants may pile up faster than they are burned. Continued burial of piled-up dead plants moves them deeper inside Earth, where geothermal energy “cooks” them. The result is a fossil fuel: oil mostly from algae, coal mostly from woody plants, and natural gas—mainly methane—from either one. This “leaking” has been going on for hundreds of millions of years, turning carbon from volcanoes into fossil fuels in rocks. Humans have discovered that it is easy to collect and burn this fossil fuel, turning it into energy we want and carbon dioxide that we release into the atmosphere. We are in the middle of a few centuries of easy living fueled by a few hundred million years’ worth of stored solar energy that evaded earlier recycling. Some of the carbon dioxide we release into the atmosphere dissolves in the ocean, some goes to grow trees, but much stays in the atmosphere for a while. We can hope mightily that most of the carbon dioxide we release will go somewhere that it won’t bother us, but this is not likely to happen. We probably are burning trees as fast as, or faster than, new ones grow. The carbon dioxide going into the ocean is slowly changing the water chemistry, making it more difficult for more carbon dioxide to enter the ocean. (It is difficult to put more cats in a kennel, to heat an alreadyhot pan, or to add more carbon dioxide to a carbon dioxide-rich ocean, because of the tendency for most things to spread out from where they are concentrated.) Carbon dioxide and water combine to form a weak acid that reacts with and dissolves rocks. Seashells and coral-reef skeletons are special rocks that living organisms build around themselves. Making the ocean more acidic will make shell growth more difficult, and will tend to dissolve the shells of dead creatures. But dissolving shells temporarily neutralize some carbon dioxide, which is part of the reason why some of our carbon dioxide goes into the ocean rather than building up in the atmosphere. If we put too much carbon dioxide into the air, the oceans will begin to run out of shells to dissolve and so will have greater difficulty absorbing carbon dioxide, and most of the carbon dioxide we produce will stay in the air for centuries, millennia, or longer. During ice ages, extra carbon dioxide was taken up by the ocean, in part because the colder water then could hold more gases, and in part because extra dust from the stronger ice-age winds fertilized plants that used more carbon dioxide. In the future, warming will work against us, releasing carbon dioxide from the ocean to the atmosphere. Some people have suggested that we humans could fertilize the oceans, duplicating the natural feat of the ice-age winds. This is indeed possible, although studies indicate that the amount of carbon dioxide likely to be taken up in a fertilized ocean is small compared to the amount we are planning to release by burning fossil fuels. Also, if too much carbon dioxide were turned into algae that sank, the decay of the algae could deplete the deep ocean of oxygen. This could cause extinctions there, and might allow release of other greenhouse gases, such as methane or nitrous oxides. In short, most of the carbon dioxide we put into the atmosphere will stay there for a while, acting as a greenhouse gas. And the more carbon dioxide we release, the more will stay in the atmosphere. The few centuries of fossil-fuel burning thus will produce a few millennia or tens of millennia of elevated atmospheric carbon dioxide concentrations. Eventually, the carbon dioxide we release will combine with volcanic or other rocks in the slow process of weathering. The weathering products including the carbon dioxide will be washed to the ocean, and (with difficulty) turned into corals or clamshells. A little bit of the carbon dioxide used by algae will escape being recycled and begin to form new fossil fuels. The atmosphere and the ocean will “forget” what we have done over tens or hundreds of thousands of years. A few hundred million years from now, when new fossil fuels have built up in new rocks, even the geology will forget us. For the coming millennia, while the atmosphere is enriched in carbon dioxide, however, the planet will be warmer than it would have been with less carbon dioxide. This is the human enhancement of the natural greenhouse effect, which the press usually shortens to “the greenhouse effect.” Almost everyone—environmentalists and industrialists, right and left, first- and thirdworlders—agrees that increasing the carbon dioxide in the atmosphere will warm the planet at least a little if all other things are held constant. Carbon dioxide in the atmosphere has little effect on incoming sunlight, but blocks some of the longer-wavelength radiation that Earth sends back to space. If carbon dioxide increases, incoming energy will exceed outgoing energy, and the difference will cause warming to a level at which Earth is able to force enough energy past the carbon dioxide to balance the incoming sunlight. Disagreements start very soon after this, however. The direct radiative effect of the humancaused increase in carbon dioxide is not likely to be too large—something vaguely in the neighborhood of one degree of warming over the next century. But, remember how chock-full of feedbacks the Earth system is. Most climate researchers expect the feedbacks to amplify the changes, giving several degrees of warming over the next century. For example, warmer air can hold more water vapor, which is a more potent greenhouse gas than carbon dioxide. Warming probably will melt some of our highly reflective snow and ice, leading to additional absorption of sunlight and, thus, to additional warming. Today, the short plants of the tundra of the far north can be buried by snow that reflects sunlight, whereas the dark trees of the taiga just to the south stick through the snow and absorb what sunlight is available; shrinkage of the tundra with warming thus may cause further warming. These feedbacks are less certain than are the direct radiative effects of carbon dioxide. Some people emphasize the difficulties in predicting the feedbacks. For example, there are hot places without much water vapor (deserts, for example), so maybe warming will not increase water vapor greatly. Also, more water vapor will make more clouds, and while some clouds (the high, thin ones) warm Earth by blocking more outgoing than incoming energy, others (the lower, thicker ones) cool the planet by blocking more incoming than outgoing energy. If an increase in carbon dioxide causes an increase in low, thick clouds, the total temperature change may not be very large. Snow melts in many places when warming occurs, but some places are cold enough that warming will not melt their snow, and may even bring more snow because warmer air often supplies more moisture. The modern scientific consensus is that positive feedbacks will amplify global warming. This is reflected in the Intergovernmental Panel on Climate Change (IPCC) reports, which are produced ultimately under the auspices of the United Nations and which represent the painfully forged results of discussions by thousands of scientists, government officials, interest groups, and private citizens. Agreeing to Disagree A word on “scientific consensus” may be useful here. All scientific ideas are subject to revision; we should never be absolutely sure that the truth has been reached. Old ideas should be tested continually, in an effort to tear them down and replace them with better ones. Ideas that survive this constant attack will be especially robust. Experience shows that if we then behave as if these surviving ideas are true, we will succeed—in curing diseases, finding clean water, building things that stand up when we want them to or blow up when we want them to, and so on. But, on the other hand, the ideas may be true, they may be reasonable approximations of the truth, or we may just be lucky. Because there is honor in tearing down old ideas to replace them with something better, science wants and needs contrarians who hammer away at the old ideas. So “scientific consensus” is not the same as 100 percent agreement, and never should be. Add to this the fact that huge money may rest on the global-warming debates. If the United States or the world decided to change the tax codes to reduce fossil fuel use, solar-energy startup companies would become more valuable, while oil wells would become less valuable. If we decided not to worry about global warming, many researchers and many lobbyists might suffer. When real money (which may add up to tens or hundreds of billions of dollars) reinforces the scientific need for contrary ideas, you can be absolutely sure that there will be loud voices on all sides of an issue. In the interest of fairness, the political process and the press tend to further confuse casual observers by giving a contrarian voice the same stature as a near-consensus voice. Some searching with an open mind is required to sort through the loud voices and identify the leading ideas. I have tried to do so (and you can judge whether I have succeeded), and I believe that the weight of scientific evidence indicates that significant human-induced future warming is the most likely outcome. Some loud voices focus on the possibility of natural changes opposing this human-caused warming. This view is absolutely right; natural changes could offset some or all of the humancaused warming. However, there is an approximately equal chance that natural changes will go the other way, greatly increasing the changes that we cause. Because the human-caused changes are likely to be much larger than any natural changes that industrial or agricultural humans have experienced, it is not too likely that the natural changes will suddenly become large enough, and go in the right way with just the right timing and distribution across Earth, to offset what we humans do. (We do expect the natural trend to be a slow, 90,000-year cooling into the depths of a new ice age, but the globally averaged rate of cooling over that time would be something around 0.01 degree per century, and maybe three to four times bigger in the polar regions, where changes are largest. Human-induced changes are likely to be one hundred or more times faster, so the next natural ice age won’t save us from ourselves. Some visionaries have even talked about saving the fossil fuels until we really need them to fight an ice age, but that would be so far in the future that it is difficult for human economies to deal with.) Ice cores and other paleoclimatic records figure prominently in the global-warming debate, and indicate that rising carbon dioxide levels will cause significant warming. The oldest direct measurements of atmospheric composition are from ice-core samples from just over 0.4 million years ago, but indirect methods agree that the warmth of the saurian sauna of 100 million years ago was caused in part by high levels of carbon dioxide. Similarly, the best explanation of the faint-young-sun paradox is that Earth did not fall into a permanent deep-freeze billions of years ago because higher carbon dioxide concentrations then allowed warmth with less sunlight. Over the last 0.4-million years, the Vostok ice-core record from Antarctica shows that temperatures and greenhouse gases have changed in similar ways. The carbon dioxide almost certainly is not the ultimate reason for the climate shifts, which were caused by orbital wiggles moving sunlight around on Earth. But the Antarctic cooled when Canada had short, cool summers even if the Antarctic was receiving extra sunshine. Credible explanations of this behavior all involve the greenhouse effects of carbon dioxide changes and associated positive feedbacks. Carbon dioxide and temperature records are certainly not identical—many things affect the climate—but the similarities of carbon dioxide and temperature records are unmistakable. Note that the controls on carbon dioxide have been different on these different time scales. Over millions to billions of years, the important balance was between carbon dioxide consumption by chemical reactions with rocks and carbon dioxide production by volcanoes. Over the hundreds of thousands of years of ice-age cycles, the rate at which the biological pump moved carbon dioxide out of the surface oceans probably has been most important. Over the centuries that we will burn fossil fuels, these other processes will be slow compared to our actions, and we will be the most important control of carbon dioxide levels. But whatever the controls on these different time scales, warmth and elevated carbon dioxide levels have gone together for billions of years. It is highly likely that this relation will continue in the future. A much tougher question is whether global warming will be a bad thing, and whether we should do something to slow or stop human influence on the climate. I offer a few of my thoughts on this in the final chapter of this book. I recognize the remaining great uncertainties, but generally support the international consensus embodied in the U.N.-sanctioned IPCC reports that the warming we humans cause will hurt some of us and help others, and that the hurt will probably outweigh the help. I believe that serious discussion is needed on human response to these changes, which may lead to human actions. This may require a slightly different view of the problem than used in traditional economic analyses, however. Discounting the Future Traditional economic analyses often suggest that we should do a little about global warming, but not a whole lot. This result comes from a peculiarity of the analyses, and from the slowness of projected changes. If I ask you to give me a pile of money, you will insist that I eventually give you back a bigger pile of money. The extra represents several things: uncertainty (maybe I’ll run away with your money); opportunity (your money would grow if you put it into a bank account or the stock market, so you expect your money to grow with me as well); and preference (you want the things you can buy with that money now, not far in the future). Because of these and other ideas (which, in some ways, are the same thing), an apple or a dollar is worth more to you today than it is in the future, and the further you look into the future, the less a dollar is worth to you. Economists call this idea discounting, and what discounting means to an economist is that we should deal with the uncertain future from climate change (and from all other causes) by building a big economy and then letting the economy handle whatever happens. With typical discount rates, things that happen more than a few decades in the future have little value, so one doesn’t worry about them too much. Hence, it may be useful to do a little about slowing human effects on climate, but we shouldn’t do a lot. True, there are “environmental” types (including some economists) who view things differently. Ethics figure into the discussion—the changes we cause will last for millennia, so do we have the right to subject future peoples to those changes? Nontraditional discount rates also show up in the discussion. Today, for example, many people have money in low-yielding bank deposits. After you subtract inflation and taxes, these people are losing money every year. Some economists would say that the people with low-yielding bank deposits are just stupid, ignorant, or lazy. But perhaps these people are living fairly well now, have lived through the Great Depression, and are really concerned that some day they could lose everything and wind up living in refrigerator cartons under freeway overpasses. An apple in the future may be worth more than an apple today to such people, because they have enough apples today and are willing to spend a little for security. Still, this is a minority view—most economists probably would argue that the slowness of climate change means that we should put most of our efforts into adaptation rather than prevention. Other reasons can be advanced for nontraditional discount rates. Some economists may be using rather optimistic projections of how much the whole world’s economy can grow in the future, and that may lead them to worry too little about future problems. Economics traditionally assumes that there is always a substitute—if something becomes scarce and expensive, someone will figure out a replacement for not too much more money. But Earth is finite, and the jump to space flight may be wildly expensive, so perhaps we should not assume that the economy can grow forever. Issues of fairness also come into play—climate change may hurt most people on Earth, but the fossil-fuel burning that contributes to climate change now is benefiting some people (those in the developed world who do most of the burning) more than others (those in the developing world). These are important questions and deserve careful scrutiny. The paleoclimatic record has added an additional critical issue to the economic debate on global warming. Our ice-core records show that huge shifts have happened in the climate—not over centuries or even decades, but over years. Over just a few years, discounting does not affect the value of things very much. If we knew that a large climate change was coming, that the change would cost our economy a lot, and that altering human behavior could prevent the cl ... Purchase answer to see full attachment