Many so-called skeptics note that environmental activists and some climate scientists exaggerate the likely effects of anthropogenic warming, distorting scientific findings and overstating the extent to which contemporary events (hurricanes, etc.) may be linked to human activity to date. But the excesses of climate activists and bad behavior by politically active scientists (and the IPCC) do not, and should not, discredit the underlying science, or justify excoriating those who reach a different conclusion. Indeed, most skeptics within the scientific community readily accept the basic science. They contest the more extreme climate projections, but accept the basic scientific claims. Take, for example, Patrick Michaels of the Cato Institute. In one of his recent books, Climate of Extremes: The Global Warming Science They Don't Want You to Know (co-authored with Robert Balling, another prominent "skeptic"), Michaels readily acknowledges that there is a warming trend and that human activity shares some of the blame.
The position espoused by Michaels, Balling and most (but not all) skeptics is that anthropogenic global warming is occurring, but it is more of a nuisance than a catastrophe. Some even argue that the net effect of climate change on the world will be positive, due to increased growing seasons, less severe winters and the like. Were I a utilitarian, and if I placed substantial faith in such cost-benefit studies, I might find these arguments convincing, but I'm not and I don't. Even if these skeptics are correct that global warming will not be catastrophic and that the net effects in the near-to-medium term might be positive, there are still reasons to act.
Accepting, for the sake of argument, that the skeptics' assessment of the science is correct, global warming will produce effects that should be of concern. Among other things, even a modest increase in global temperature can be expected to produce some degree of sea-level rise, with consequent negative effects on low-lying regions. Michaels and Balling, for instance, have posited a "best guess" that sea levels will rise 5 to 11 inches over the next century. Such an increase in sea levels is likely manageable in wealthy, developed nations, such as the United States. Poorer nations in the developing world, however, will not be so able to adapt to such changes. This is of particular concern because these effects will be most severe in those nations that are both least able to adapt and least responsible for contributing to the concentration of greenhouse gases in the atmosphere.
It is a well established principle in the Anglo-American legal tradition that one does not have the right to use one's own property in a manner that causes harm to one's neighbor. There are common law cases gong back 400 years establishing this principle and international law has long embraced a similar norm. As I argued at length in this paper, if we accept this principle, even non-catastrophic warming should be a serious concern, as even non-catastrophic warming will produce the sorts of consequences that have long been recognized as property rights violations, such as the flooding of the land of others.