Global climate change a new type of environmental problem

Of all the environmental issues that have emerged in the past few decades, global climate change is the most serious, and the most difficult to manage. It is the most serious because of the severity of harms that it might bring. Many aspects of human society and well being - where we live, how we build, how we move around, how we earn our livings, and what we do for recreation - still depend on a relatively benign range of climatic conditions, even though this dependence has been reduced and obscured in modern industrial societies by their wealth and technology. We can see this dependence on climate in the economic harms and human suffering caused by the climate variations of the past century, such as the "El Nino" cycle and the multi-year droughts that occur in western North America every few decades. Climate changes projected for the twentyfirst century are much larger than these twentieth-century variations, and their human impacts are likely to be correspondingly greater.

Projections of twentyfirst-century climate change are uncertain, of course. We will have much to say about scientific uncertainty and its use in policy debates, but one central fact about uncertainty is that it cuts both ways. If projected twentyfirst-century climate change is uncertain, then the actual changes might turn out to be smaller than we now project, or larger. Uncertainty about how the climate will actually change consequently makes the issue more serious, not less. Present projections of twentyfirst-century climate change include, at the upper end of the range of uncertainty, sustained rapid changes that appear to have few precedents in the history of the Earth, and whose impacts on human well-being and society could be of catastrophic proportions.

Climate does not just affect people directly: it also affects all other environmental and ecological processes, including many that we might not recognize as related to climate. Consequently, large or rapid climate change will represent an added threat to other environmental issues such as air and water quality, endangered ecosystems and biodiversity, and threats to coastal zones, wetlands, and the stratospheric ozone layer.

In addition to being the most serious environmental problem we have yet faced, climate change will also be the most difficult to manage. Environmental issues often carry difficult tradeoffs and political conflicts, because solving them requires limiting some economically productive activity or technology that is causing unintended environmental harm. Such changes are costly and generate opposition. But for the issues we have faced previously, technological advances and intelligent policies have allowed great reductions in environmental harms at modest cost and disruption, so these tradeoffs and conflicts have turned out to be quite manageable. Controlling the sulfur emissions that contribute to acid rain in the United States of America provides a good example. When coal containing high levels of sulfur is burned, sulfur dioxide (SO2) in the smoke makes the rain that falls downwind of the smokestack acidic, harming lakes, soils, and forests. Over the past 20 years, a combination of advances in technologies to remove sulfur from smokestack gases, and well-designed policies that give incentives to adopt these technologies, burn lower-sulfur coal, or switch to other fuels, have brought large reductions in sulfur emissions at a relatively small cost and with no disruption to electrical supply.

Climate change will be harder to address because the activities causing it -mainly burning fossil fuels for energy - are a more essential foundation of world economies, and are less amenable to any simple technological corrective, than the causes of other environmental problems. Fossil fuels provide nearly 80 percent of world energy supply, and no technological alternatives are presently available that could replace this huge energy source quickly or cheaply. Consequently, climate change carries higher stakes than other environmental issues, both in the severity of potential harms if the changes go unchecked, and in the apparent cost and difficulty of reducing the changes. In this sense, climate change is the first of a new generation of harder environmental problems that human society will face over this century, as the increasing scale of our activities puts pressure on ever more basic planetary-scale processes.

When policy issues have high stakes, it is typical for policy debates to be contentious. Because the potential risks of climate change are so serious, and the fossil fuels that contribute to it are so important to the world economy, we would expect to hear strong opposing views over what to do about climate change -and we do. But even given the issue's high stakes, the number and intensity of contradictory claims advanced about climate change is extreme. The following published statements give a sense of the range of views about climate change.

From former US Vice-President Al Gore:

[T]he vast majority of the most respected environmental scientists from all over the world have sounded a clear and urgent alarm ... [T]hese scientists are telling the people of every nation that global warming caused by human activities is becoming a serious threat to our common future ... I don't think there is any longer a credible basis for doubting that the earth's atmosphere is heating up because of global warming ... So the evidence is overwhelming and undeniable. Global warming is real. It is happening already and the anticipated consequences are unacceptable.1

From former US Secretary of Defense and of Energy James Schlesinger:

What we know for sure is quite limited ... We know that the theory that increasing concentrations of greenhouse gases like carbon dioxide will lead to further warming is at least an oversimplification. It is inconsistent with the fact that satellite measurements over 24 years show no significant warming in the lower atmosphere, which is an essential part of the global-warming theory.2

From US Senator James Inhofe:

[A]nyone who pays even cursory attention to the issue understands that scientists vigorously disagree over whether human activities are responsible for global warming, or whether those activities will precipitate natural disasters ... So what have we learned from the scientists and economists I've talked about today?

1 The claim that global warming is caused by man-made emissions is simply untrue and not based on sound science.

2 CO2 does not cause catastrophic disasters - actually it would be beneficial to our environment and our economy ...

With all of the hysteria, all of the fear, all of the phony science, could it be that man-made global warming is the greatest hoax ever perpetrated on the American people? It sure sounds like it.3

From the Wall Street Journal:

... the science on which Kyoto is based has never been able to explain basic questions. Most glaring is why the Earth warmed so much in the

1 Global Warming and the Environment, speech by Al Gore, Beacon Hotel, New York City, Jan. 15, 2004.

2 Commentary: Cold facts on global warming, James Schlesinger, Los Angeles Times, Jan. 22,2004, p. B17.

3 The Science of Climate Change, floor statement by Senator James M. Inhofe, July 28, 2003.

early part of the 20th century, before the boom in carbon dioxide emissions. Another is why the near-earth atmosphere (measured by satellites) isn't warming as much as the Earth's surface. There's also the nagging problem that temperatures more than 1,000 years ago appear to have been as warm, if not warmer, than today's.4

From the National Post of Canada:

Global warming, as increasing numbers of actual scientists will tell you, is not happening.5

From the well-known scientific skeptic, S. Fred Singer:

[T]he Earth's climate has not warmed appreciably in the past two decades, and probably not since about 1940.6

That the climate is currently warming rests solely on surface thermometer data. It is contradicted by superior observations from weather satellites and independent radiosonde data from weather balloons. Proxy (non-thermometer) data from tree rings, ice cores, etc., all confirm that there is no current warming. That the 20th century was the warmest in the past 1,000 years derives entirely from misuse of such proxy data The claim that climate models ... accurately reproduce the temperature record of the past 100 years, is spurious.7

From Nobel laureate F. Sherwood Rowland, of the University of California at Irvine:

The earth's climate is changing, in large part because of the activities of humankind. The simplest measure of this change is the average temperature of the Earth's surface, which has risen approximately 0.7 degrees Celsius over the past century, with most of this increase occurring in the past two decades. In other words, the Earth is undergoing global warming ... The possibility exists for notable deterioration of the climate in the United States even on a decadal time scale ... [T]he climate change problem will be much more serious by the year 2050 and even more so by 2100.8

4 Global warming glasnost, editorial, Wall Street Journal, Dec. 4, 2003, p. A16.

5 The Conservatives must attack Kyoto, editorial, National Post of Canada, March 19, 2004.

6 S. Fred Singer, testimony before the US Senate Committee on Commerce, Science, and Transportation, July 18, 2000.

7 S. Fred Singer, Bad data make global warming a cold case, letter to the editor, Wall Street Journal, Nov. 10, 2003, p. A17.

8 F. Sherwood Rowland, Climate change and its consequences: issues for the new U.S. Administration, Environment 43(2), March 2001, pp. 29-34.

And from Jerry Mahlman, former director of the US Geophysical Fluid Dynamics Laboratory at Princeton:

... we know that the earth's climate has been heating up over the past century. This is happening in the atmosphere, ocean and on land ... [I]f the climate model projections on the level of warming are right, sea level will be rising for the next thousand years, the glaciers will be melting faster and dramatic increases in the intensity in rainfall rates and hurricanes are expected ... Unfortunately, these projections are based on strong science that refuses to go away. Oh sure, there are people insisting that warming is just a part of natural weather cycles, but their claims are not close to being scientifically credible ... These people remind me of the folks who kept trying to cast doubt on the science linking cancer to tobacco use. In both situations, the underlying scientific knowledge was quite well established, while the uncertainties were never enough to render the problem inconsequential. Yet, this offered misguided incentives to dismiss a danger ... Global warming is unpleasant news. The costs of doing something substantial to arrest it are daunting, but the consequences of not doing anything are staggering.9

One of the most striking aspects of this debate is the intensity of disagreements expressed over what we might expect to be simple matters ofscientific knowledge, such as whether the Earth is warming or not. Such heated public confrontation over the state of scientific knowledge and uncertainty - not just between political figures and policy commentators, but also between scientists - understandably leaves most concerned citizens confused. The state of public and political debate on the issue makes it hard for non-specialists to understand what the advocates are arguing about, or to judge the strength of competing arguments.

Our goal in this book is to clarify the climate-change debate. We seek to help the concerned, non-expert citizen to understand what is known about climate change, and how confidently it is known, in order to develop an informed opinion of what should be done about the issue. We will summarize the state of knowledge and uncertainty on key points of climate science, and examine how some of the prominent claims being advanced in the policy debate - including some in the quotes above - stand up in light of present knowledge. Can we confidently state that some of these claims are simply right and others simply wrong, or are these points of genuine uncertainty or legitimate differences of interpretation?

9 Claudia Dreifus, A Conversation with Jerry Mahlman: listening to climate models and trying to wake up the world, New York Times, Dec. 16, 2003, p. F2,

We will also summarize present understanding and debate over the likely impacts of climate change and the responses available to deal with the issue - matters that go beyond purely scientific questions, but which can be informed by scientific knowledge.

We will also examine how scientific argument and political controversy interact. This will help to illuminate why seemingly scientific arguments play such a conspicuous role in the climate-change policy debate, and in particular how such extreme disagreements can arise on points that would appear to be matters of scientific knowledge. What do policy advocates hope to achieve by arguing in public over scientific points, when most of them - like most citizens - lack the knowledge and training to evaluate these claims? Why do senior political figures appear to disagree on basic scientific questions when they have ready access to scientific experts and advisors to clarify these for them? And finally, what are the effects of such blended scientific and political arguments on the policy-making process?

While there is plenty of room for honest, well-informed disagreement over what should be done about global climate change, it is our view that the issue is made vastly more confused and contentious than it need be by misrepresentations of the state of scientific knowledge in policy debate - in particular, by exaggeration of the extent and significance of scientific uncertainty on key points about the global climate and how it might respond to further human influences.

Before we can engage these questions, the next two sections of this chapter provide some necessary background. Section 1.1 provides a brief background on the Earth's climate and the basic mechanisms that control it and can change it. Section 1.2 provides a brief history of existing policy and institutions concerned with global climate change, to provide the policy context for the present debate.

Continue reading here: Background on climate and climate change

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