Global temperatures appear to be being negatively impacted by the buildup of so-called "greenhouse gases" in the atmosphere, with carbon dioxide being the most prominent of them. Current assumptions about physical and biological consequences, potential societal costs, and estimated abatement costs are summarised in this paper. For a "worst case" scenario to be economically viable, it would be impossible to assess every conceivable non-linear synergistic impact. It seems probable that the consequences are within the "affordable" range, at least in the industrialised nations of the world, under the "most favourable" (but not necessarily "likely") scenario of slow-paced climate change. Even if there is some doubt about the certainty of something happening, this remains true. In the "third world," where the idea of cost is dubious at best, quantitative evaluation presents a formidable obstacle.

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Keywords: Greenhouse, Gases, Atmosphere, Environment.