One of the main points of contention among scientists is what will happen to the planet as a result of global warming. Some believe that the earth will actually benefit if the climate continues to grow warmer. Others insist that the opposite is true, saying that if the planet continues to heat up, the effects will be catastrophic. NASA sums up these very different perspectives:
Many see [global warming] as a harbinger of what is to come. If we don't curb our greenhouse gas emissions, then low-lying nations could be awash in seawater, rain and drought patterns across the world could change, hurricanes could become more frequent. . . . On the other hand, there are those, some of whom are scientists, who believe that global warming will result in little more than warmer winters and increased plant growth. They point to the flaws in scientists' measurements, the complexity of the climate, and the uncertainty in the climate models used to predict climate change. They claim that attempting to lower greenhouse emissions may do more damage to the world economy and human society than any amount of global warming. In truth, the future probably fits somewhere between these two scenarios. 30
The climate models to which NASA refers are powerful computer programs used to simulate climate and predict future climate changes. Models can be used to simulate temperature changes that occur from both natural and anthropogenic causes. Scientists enter data on different conditions, such as atmospheric concentrations of greenhouse gases, ocean currents, cloud cover, energy from the sun, and ocean circulation, as well as others. Then, as they change and adjust the variables, they can simulate what might happen when actual climate conditions change. NASA compares climate models to the computer programs used by detectives to envision what
There are many different types of climate models. The simplest models can be run on personal computers, and are designed to focus on one particular time frame, or to investigate a specific phenomenon. The most sophisticated climate models are supercomputers known as general circulation models (GCMs). Climate models have evolved from the same sort of computer programs that are used to make weather forecasts. Richard C.J. Somerville says that just as people criticize meteorologists when weather predictions are wrong, some global warming skeptics denounce climate models as useless—and he insists that is not true. He also says that just as weather simulation programs have improved markedly over time, climate models are also being improved and perfected. He shares his perspective about their use for predicting a future climate: "The model in the end is a computer program. We can't take the atmosphere or the whole planet and put it in a test tube and do experiments on it. So instead, we simulate it in a computer. That's turned out to be the best way of incorporating all the various complexities." 31
Climate prediction is not an exact science, and no one who uses climate models will say that they are perfect. S. Fred Singer is highly skeptical about the ability of climate models to accurately predict future climates. He bases his belief on the fact that the predictions of models do not always agree with what is actually happening with the climate. He says, for instance, that current models show that the climate should be warming by one degree Fahrenheit per decade, in the middle troposphere, but that is not what observations actually show. Singer explains his opinion about these models: "Until the observations and the models agree, or until one or the other is resolved, it's very difficult for people—and for myself, of course—to believe in the predictive power of the current models. Now, the models are getting better. And perhaps in ten years we will have models that can be trusted, that is, that agree with actual observations." 32
Richard S. Lindzen is another scientist who is skeptical about the effectiveness of climate models. He has often stated his belief that the models are merely experimental tools with questionable value. Lindzen feels that computer predictions should be viewed only as possibilities—not facts—yet he says this is not often the case and he shares his thoughts about why: "Unfortunately, there is a tendency to hold in awe anything that emerges from a sufficiently large computer. There is also a reluctance on the part of many modellers to admit to the experimental nature of their models lest public support for their efforts diminish." 33
Just as Singer, Lindzen, and some other scientists are skeptical about the effectiveness of computer models, they also doubt the scientists who believe that global warming will be harmful for the planet. They base their beliefs on the fact that there has never been a time in history when the earth did not experience widely fluctuating temperatures. Humans, animals, and plant life have always adapted to changing conditions, and these scientists believe this will continue to happen. Plus, because carbon dioxide is necessary for the survival of all living things, their perspective is that the more CO 2 there is in the atmosphere, the more the planet—and its inhabitants—will benefit.
Drs. Craig D. Idso and Keith E. Idso, from the Center for the Study of Carbon Dioxide and Global Change, say that excess carbon dioxide in the atmosphere will have nothing but positive results. They believe that the United States should not be criticized for the amount of CO 2 it is adding to the atmosphere, as they explain:
The United States should be applauded for its emissions of CO 2 ; for it is the ongoing rise in the air's CO 2 content that will ultimately prove the salvation of the planet. How do we know that? Because carbon dioxide is the very elixir of life; the primary raw material upon which nearly all plant life—and, hence, nearly all animal life (including man!)—depends for its existence. And the more CO 2 there is in the air, the better plants grow; and, consequently, the more food there is for human and animal consumption. 34
Dr. Thomas Gale Moore, an economist at Stanford University's Hoover Institution, agrees with this perspective. Moore says that virtually all plants will thrive in an environment where there is an abundance of carbon dioxide. He believes that global warming will bring shorter winters, which would mean longer growing seasons for crops. Also, winters would be warmer, so according to Moore, there would be more affordable heating bills, less ice and snow to hinder drivers, and fewer airline delays because of bad weather. He sums up his thoughts: "Pundits, politicians and the press have argued that global warming will bring disaster to the world, but there are good reasons to believe that, if it occurs, we will like it. Where do retirees go when they are free to move? Certainly not to Duluth [Minnesota]. People like warmth. When weather reporters on TV say, 'it will be a great day,' they usually mean that it will be warmer than normal." 35
Scientists do not dispute the fact that plant life thrives on carbon dioxide. What they disagree about is how much is too much. Many believe that the amount of CO 2 and other greenhouse gases that humans are adding to the atmosphere go far beyond what the planet can handle. This is the viewpoint of Dr. Tom Wigley, a climatologist and senior scientist with the National Center for Atmospheric Research. He acknowledges that not all global warming is harmful nor is an increase in CO 2 necessarily bad, because carbon dioxide accelerates plant growth. Wigley explains what does concern him: "What we're afraid of is that if the planet warms too much, we're going into unknown territory. We can't predict the climate well enough to know what to expect. So we certainly don't want to go too far down the road, down the pathway of global warming. We have time to think about what to do. But eventually, we have to do something dramatic." 36
Tom Crowley, a climate researcher in the oceanography department at Texas A&M, is another scientist who is concerned about the earth's future because so much is still unknown. There was a time when he was doubtful about the existence of global warming but that time has passed, as he explains: "To me the question of whether global warming is happening is receding as the central question. In my view, it's already here—and I didn't believe that two years ago. Now the question is: How will it affect us?" 37
Scientists who are the most alarmed about global warming predict that the earth is headed for catastrophe if the temperature keeps rising—which they are convinced it will continue to do. They know that greenhouse gases, such as carbon dioxide, have been building up for several hundred years. Once they are in the atmosphere, most of them remain there for a very long time, and billions of tons of these gases are still being emitted every year. Also, over the past fifty years the planet warmed more rapidly than at any other time in history. Many scientists are convinced that temperatures will continue to rise at the same rate—or perhaps even faster. Dr. Henry Jacoby of the Massachusetts Institute of Technology (MIT) says that even though scientists cannot be sure how serious global warming is, there are reasons to be concerned about the future and he explains why:
The potential is that it might be quite serious. That is, the change in climate, temperature, and rainfall . . . the potential for changes in storminess, extreme events like droughts and floods . . . the potential over the century is substantial. We don't know [for sure], but the potential is there. And since we're building up this stock ofgreenhouse gases in the atmosphere and they don't go away fast, it makes a big difference when you start to deal with it. 38
One group that has issued a strong warning is the Intergovernmental Panel
on Climate Change (IPCC), which is composed of scientists from all over
the world. Since 1988, the IPCC has studied the global climate including
why it changes, different factors that influence those changes, how a
warming climate will affect living things and the environment, and what
can be done to stop it. In March 2001, the IPCC concluded that most of the
warming during the past fifty years has been caused by human activities.
The group also projected that by the year 2100, the earth's average
surface temperature will have increased between
2.5 degrees and 10.4 degrees Fahrenheit from 1990 temperature readings.
Some occurrences such as warming ocean waters, disappearing sea ice, melting permafrost, and extreme weather are already happening—and as the climate continues to grow warmer, the IPCC warns that these phenomena will become much worse. For instance, the group projects that in the next hundred years more than 50 percent of the world's glaciers will disappear, and sea levels will rise between 3.5 to 34 inches. If that happens, the result will be erosion of coastlines, destruction of wetlands, and severe flooding. Because as much as 50 percent of the world's population lives in coastal communities, floods could force millions of people to abandon their homes.
NASA offers a more conservative prediction about ocean waters, saying that although sea levels are likely to rise, the results will be nothing like those dramatized in movies: "The Statue of Liberty won't be up to her neck in water, and we won't all be living on flotillas on an endless sea. . . . The rise will mainly be due to seawater expanding from the increased ocean temperatures and run-off from the melting of continental glaciers and a slight melting of the Greenland Ice Sheet." 39 NASA says that for the most part, ice sheets in Antarctica will probably stay in place, and may even grow because of increased precipitation over the next century. The agency adds, however, that if global warming caused unusually rapid melting of polar ice sheets, sea levels would rise dramatically.
Even though NASA scientists say that higher levels of carbon dioxide would benefit some plant life, they caution that most changes caused by increased CO 2 will likely be for the worst. If a steadily warming planet leads to the flooding of coastal wetlands, countless species of fish and birds would be driven out, and many types of wetland vegetation would
John Firor explains how continued global warming would affect the world's forests:
By studying the last ice age, we know that forests in the eastern U.S. migrated northward as the weather warmed. . . . Some who study the impacts of climate change note that these forests migrated at what seems like a rapid pace—but the climate changes we are now forcing on the Earth because of greenhouse gases are happening many times faster than the changes from the ice age. What that means is that forests will probably not be able to migrate fast enough to reproduce, so they will be lost. 40
Stephen H. Schneider shares Firor's views. He offers his thoughts about what a warming planet could mean:
How are the species of trees . . . and birds and so forth . . . going to migrate? In history, they just migrated. Now they have to cross factories, farms, freeways, and urban settlements. So if you have the combination of fragmented habitats with nature getting into smaller and smaller patches, now you change the climate ten times faster than the history for which they have experience, this seems to me an absolute prescription for an extinction crisis where we lose a large fraction of the species now on earth. 41
Just as plant and animal species may not be able to migrate fast enough to survive, those that live in the world's oceans and lakes may not be able to tolerate water that is warmer than normal. For instance, many fish species are highly sensitive to temperature changes; and when the changes are extreme, the fish can die. In addition, if the oceans continue to warm, the production of phytoplankton would be reduced—and that could have a devastating effect on the entire food chain. There have been major declines in populations of Alaskan salmon and other types of fish, as well as seabirds and marine mammals, and some scientists believe this is a direct result of the depleting supply of phytoplankton.
Wildlife and plants are not the only living things that could have a difficult time adapting if the average global climate became warmer. It could also cause severe problems for human beings. One possible result of a warmer global climate would be an increase in heat waves. This phenomenon could potentially affect every region of the world; but it would be especially devastating to people in Africa and Asia where average year-round temperatures are already extremely hot. Many countries such as Afghanistan, Ethiopia, and India have large populations. Because they also have high poverty rates, these people are particularly vulnerable to heat waves and droughts. According to the Union of Concerned Scientists, residents of these areas are already suffering as a result of rising temperatures. For example, extensive fires affected people along the west coast of South Africa during January 2000, and during 2001 Kenya suffered from the worst drought in sixty years. The group also cites a May 2002 heat wave in southern India that resulted in the highest one-week death toll ever recorded.
Higher temperatures can also subject human beings to increased outbreaks of deadly infectious diseases such as malaria, dengue fever, and encephalitis.
No matter where scientists stand on the global warming issue, they all have strong opinions about it. Some believe that more carbon dioxide and warmer temperatures will be good for the planet, while others believe that the future holds great harm. At this point, there is more guesswork involved than anything else—something even the most astute scientists do not deny. Schneider says that many people think of the study of global warming as a fuzzy, uncertain science, which, in many ways, it is. He believes, however, that even though there are still many doubts about global warming, the potential is serious enough that it warrants attention, as he explains: "The dilemma rests, metaphorically, in our need to gaze into a very dirty crystal ball; but the tough judgment to be made here is precisely how long we should clean the glass before acting on what we believe we see inside." 42