More from David Ridenour at COP-12 in Nairobi:

Sir Nicholas Stern, author of the much-publicized “Stern Review on the Economics of Climate Change,” conceded that uncertainties remain on both the science and economics of climate change in an afternoon presentation here at the U.N. Global warming conference.Stern began his presentation by acknowledging that global action to curb greenhouse gas emissions has been delayed due to the long-term nature of the problem and the ongoing scientific and economic uncertainties of climate change.

Referring to climate change as an externality, Stern said the real question is “what could be the costs of these externalities? This is a matter of the economics of risk.”

Wednesday, Secretary General Kofi Annan lashed out at what he called “a few die hard skeptics… Trying to sow doubt.” He said these skeptics “should be seen for what they are: out of step, out of arguments, and out of time.”

One assumes he wasn’t referring to Stern, but one wonders. The key difference between Stern and the so-called “skeptics” is not that they disagree on the existence of uncertainty. Both acknowledge there is some. The key difference is that Stern believes in applying the precautionary principle — regulating emissions “in case” it is needed to avert global catastrophe.

Stern argues that the risk probability is significant enough to warrant drastic action. Reasonable people can disagree.

His prescription? Stern calls for stabilizing anthropogenic emissions at 550 parts per million (it’s currently 430 ppm). This, he argues, is what is needed to limit the increase in global temperature to 2-3 degrees Celsius.

This can be achieved, he claims, at a cost of just 1 percent of world GDP.

But given the current technology, this figure seems highly dubious without major technological advances. Demand for energy continues to rise and no economically and politically acceptable substitute currently exists.

I told Stern that I believed his figure of 1 percent of GDP was unrealistic and asked him about his technological assumptions and if nuclear energy was built into them.

The first part of his answer qualifies as the “Duck of the Day.”

“I don’t think it’s unrealistic… It draws on a very broad range of literature… A lot depends on investment, flexibility of structures, and good policy,” Stern responded. “There’s considerable uncertainty… But our [findings] are consistent with figures elsewhere.”

And the underlying technological assumptions would be?

Stern finally did acknowledge, however, that stabilizing emissions would require, “the whole range… Wind, solar, nuclear have to play a part.”

The Stern Review briefing also included a presentation by Vicky Pope of the Hadley Centre, upon which the Stern Review depended for the scientific part of its report.

Like Stern, Pope began her presentation pointing out the uncertainties of emissions, “science in models,” and natural variability — apparently to add an air of respectability the Hadley Centre’s research.

But she assured all in attendance that the group’s projections of significant, possibly catastrophic warming were based on “plausible science.”

That’s similar to the phase used by Kofi Annan yesterday.

Again, we’re being asked to take immediate, possibly economically devastating greenhouse gas reductions based on plausible science?

In case anyone actually listened to and took note of her statement that the science is uncertain, Pope threw this in: “[An increase of] 5 degrees Celsius… [Which would result] from business as usual… is the difference between now and the last Ice Age.”

Talk about contradictory messages.

And now the jaw-dropper of the day…

The Stern panel also included a presentation by an environmental specialist from the Peoples Republic of China by the name of Pan Jiahua who made one comment that drew gasps from the audience.

Mr. Jiahua asserted that reducing greenhouse gas emissions requires more than technological advancements. It requires, he said, reducing demand, which can be achieved, in part, by limiting population growth. He went on to say that China’s one-child policy has reduced energy demand by 300 million people.

The comment drew gasps from some in the audience. Under China’s one-child policy, millions of baby girls have been put to death by parents seeking male offspring.

At the conclusion of the panel, I gave Sir Nicholas Stern one of our “Kyoto Protocol Survival Kits.” He graciously accepted.