In his latest Newsweek column, Robert Samuelson says that global-warming deniers have little influence on the public debate, so it's silly to worry about them ("the alleged cabal's influence does not seem impressive"). But one of the more interesting revelations in Newsweek's cover story was the degree to which GOP policymakers have relied on and internalized the arguments of industry-funded deniers, according to a former Republican staffer. That's certainly a big deal. In any case, Samuelson raises some more pertinent questions here:

The global-warming debate's great un-mentionable is this: we lack the technology to get from here to there. Just because Arnold Schwarzenegger wants to cut emissions 80 percent below 1990 levels by 2050 doesn't mean it can happen. At best, we might curb emissions growth.

Consider a 2006 study from the International Energy Agency. With present policies, it projected that carbon-dioxide emissions (a main greenhouse gas) would more than double by 2050; developing countries would account for almost 70 percent of the increase. The IEA then simulated an aggressive, global program to cut emissions based on the best available technologies: more solar, wind and biomass; more-efficient cars, appliances and buildings; more nuclear. Under this admitted fantasy, global emissions in 2050 would still slightly exceed 2003 levels.

That's a decent concern. But first, a quibble. The IEA report (summary here) actually laid out six scenarios, and under the most rosy-eyed--called the "TECH plus" scenario, which makes some optimistic assumptions about breakthroughs in renewable energy and the like--emissions would be 27 percent lower in 2050. This seems to be the "admitted fantasy" scenario, although even that doesn't appear terribly far-fetched. (Compared to other analyses, for instance, the IEA report is pessimistic about the gains that could come from advances in, say, efficiency and carbon capture.)

But even if Samuelson was right, and in the best possible world we could only hold emissions at 2003 levels in 2050, well, that would be worrisome--and probably mean that irreversible warming, some sea-level rises, and the like were on the way--but it would still be better than doing nothing or doing little (which Samuelson seems to prefer). This year's IPCC report was pretty clear about this: 3 additional degrees of warming, while bad, would still be preferable to, say, 4 degrees of warming or more.

--Bradford Plumer