Uncertainties in Global Climate Change Estimates

by Elizabeth Paté-Cornell

Climatic Change
Volume 33, Number 2, 145-149, DOI: 10.1007/BF00140245

Full text (PDF format) available.


“The models used in the assessment of the effects of global climate change are based on limited knowledge of the fundamental phenomena, for instance, the role of the clouds and of the oceans (IPCC, 1996). Although a general consensus seems to exist among the scientists involved, the very existence of this consensus does not
constitute proof that it represents nature’s reality. Uncertainties remain and many of the generally accepted assumptions need to be revisited. The effects of some of these uncertainties are represented in the results, but often under the form of confidence intervals. Yet, all parts of these intervals do not have the same probability, and many points outside of these intervals do not have a zero probability. Much work needs to be done to improve the information used for public policy in response to a threat of global climate change. Some of it is fundamental research, some of it is better representation of the information that already exists.

When science can progress quietly, independently from the pressures of public policy making, the scientific community has ample time to fight its internal battles and to prove or disprove each element of the problem. There is no need to synthesize the state of knowledge until the problem is considered resolved by most. In that context, errors may not matter much. The speed of light, for example, was measured over many years with different levels of accuracy (Henrion and Fischhoff, 1986) until available instruments and methods allowed general confidence in the results.

When decisions need to be made along the way, based on partial and incomplete information for private purposes or public sector regulations, one does not have the luxury of taking the time to reach a complete, unquestioned consensus. In that case, the available information, imperfect as it is, must be synthesized at a particular stage to represent as closely as possible the state of knowledge at that time.”

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