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2 Science and policy.

Motivation for a treaty limiting greenhouse gas emissions stems from evidence that the global climate is warming and the strengthening inference that human activity is a significant contributing factor. In turn, the degree to which interventions are required depends firstly on an evaluation of both points, and secondly on an assessment of the damages caused by global warming and the costs and benefits of altering its mutable components.

The conceptual foundation for the contribution of human activity to global warming is not controversial in itself and relates to the greenhouse effect. Briefly, as the earth constantly receives energy from the sun and radiates energy back into space, water vapor, clouds and long-lived gases, including carbon dioxide, work to reduce the outflow of radiated light, creating an energy imbalance known as the greenhouse effect. In 1861, John Tyndall speculated that the accumulated release of carbon dioxide from combustible fossil fuels might increase the energy imbalance, resulting in a warming of the earth's surface. Later, the Swedish physicist, Svante Arrhenius (1896) provided a formal model of the phenomenon. Arrhenius predicted a gradual warming of the climate, but did not view the consequences as threatening. Later, as global consumption of fossil fuels increased and the earth's cooling and warming mechanisms became better understood, the subject was further revived.

In 1957, an important paper by Revelle and Suess (1957) suggested that the oceans' capacity to absorb carbon dioxide from the atmosphere was more limited than previously thought. The authors went on to stress the potential risks and uncertainties associated with a continuing buildup of greenhouse gases. In the ensuing years, measurements of atmospheric carbon dioxide taken at the Mauna Loa Observatory starting in 1958 revealed increasing concentration of carbon dioxide in the atmosphere. Later on, corroborating evidence from ice-core analysis suggested a trend of building accumulations going back to the Nineteenth Century (Siegenthaler and Oeschger 1987).

Nevertheless, predicting the consequences of increased concentrations of atmospheric carbon dioxide and induced global warming proved a difficult task. Hurdles included inexact historic climatic measures and an incomplete understanding of the complex natural relationships among the mechanisms that heat and cool the earth's oceans and atmosphere. (2) By the close of the 1970s, no consensus had emerged among scientists as to the effects increased concentrations of greenhouse gases might have on climate and no formal mechanism existed to reach one. By extension, economic analysis of the consequences of climate change lacked a common starting point. (3)

A series of conferences sponsored by the World Meteorological Organization (WMO), the United Nations Environment Program and the International Council for Science led to the establishment of an Advisory Group on Greenhouse Gases in 1985 and ultimately the establishment of the Intergovernmental Panel on Climate Change (IPCC) in 1988, which is the formal mechanism by which studies concerning human-induced climate change are reviewed by experts with the goal of providing an objective evaluation to policy makers. (4) The first panel report was submitted to the UN General Assembly in 1990 and was instrumental in the eventual negotiation of an international treaty, the United Nations Framework Convention on Climate Change (UNFCCC), intended to protect the global climate by limiting greenhouse gas emissions. (5) Significant additions to the treaty, known as the Kyoto Protocol, were negotiated in 1997 and entered into force in February 2005, following IPCC reports in 1995, 1997 and 2001. The most recent IPCC report was issued in 2007.

Of special interest for this paper is the structure of the IPCC and the topics it is designed to review, since much of the literature cited here directly addresses questions posed by the IPCC. As a practical matter, the work of the IPCC is carried out by separate groups of experts aligned around three general topics. The first working group is concerned primarily with evaluating the drivers of climate change and evaluating on-going evidence of global warming. Much of the evaluation of physical models of climate change takes place within this group. The remaining groups deal with predicted consequences. Working Group II assesses current knowledge about and predicted effects of climate change on nature and on human welfare, vulnerability and adaptability. Much of the economic analysis evaluated by this group concerns an accounting of economic gains and losses due to climate change. The third working group focuses on mitigation. Related economic studies reviewed by the group include both general equilibrium studies and sectoral studies of mitigation costs. The effects of market mechanisms are also reviewed by this group. Experts who draft and review initial reports are chosen by member governments and governments participate in the reviews of final drafts. As a general practice, draft summaries intended for policy makers are closely reviewed by national representatives external to the working groups and actively debated before their release. The panel is not the only group engaged in assessing the likely economic impact of climate change and other summary evaluations exist, most notably the Stern Review on the Economics of Climate Change issued by the British Government in November 2006.

Before proceeding to the next section, it is useful to draw some parallels between the physical and social sciences as they relate to climate change. In both instances, expected outcomes lie largely outside current experience. For this reason, numerical models of highly complex relationships--either climatic or economic are relied upon. While a discussion of climate models falls outside the scope of this paper, we return to modeling issues later in the paper.
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Title Annotation:Carbon Markets, Institutions, Policies, and Research
Publication:Carbon Markets, Institutions, Policies, and Research
Date:Oct 1, 2008
Previous Article:1 Introduction.
Next Article:3 Features of the climate change framework.

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