If they expect the economy to fall apart due to climate change and other stressors, then it's a perfectly reasonable plan, I'd say.

(Hmmm... There's not emoticon for "I'm kidding, but it's not actually funny")

I think the first guy to do the intensity calculation made a valuable contribution.  He showed that some societies were able to prosper with a much lower energy footprint than others.

You can use intensity to argue that Americans could halve their energy use without pain (bringing themselves in-line with Japanese or European levels).

In fact, I've used intensity in arguing with the "we can't do anything about global warming because it would destroy the economy" types.

On the other hand, obviously, you can use that (valuable) number to divert the eye from the final goal.  That's the scam, not the number.

Dr. Dessler said it right - CO2 intensity per GDP has indeed been falling on its own without any dramatic intervention on our part. This is addressed in the work on the so-called Kaya Identity, which parses global CO2 emissions as (by definition) arising from:

(CO2 intensity per unit energy consumption) times
(energy intensity per unit GDP) times
(GDP per capita) times
population

We have to accept that population is just going to increase, and GDP per capita is most likely to keep growing quite a lot for quite a while. So the product of the first two terms, which APEC is naming as a single element of CO2 intensity of GDP, is what we have to manage. However, since the population and world GDP are set to keep growing, we can reduce the intensity somewhat without getting any absolute reduction in total CO2 output, and that's just not enough. The only way to cut CO2 is to cut the intensity term by a good bit more than the rate of growth of the economy.
Unfortunately with the uncertainties around forecasting future GDP, we risk having way higher CO2 emissions if we only commit ourselves to a fixed intensity target instead of a goal for CO2 emissions themselves.
We have fairly tight bounds on the expected world population growth for the coming century, barring severe catastrophe: somewhere between 9.5 and 10.5 billion population by 2100.
The value of (GDP per capita) is far more open-ended, with lots of room for either great increases or setbacks due to bad times, energy crises, wars, whatever. However, I'm seeing detailed estimations that foresee vast increases in world GDP per capita over the coming century.

The energy per unit of economic output is the one that is falling consistently on its own, as a function of technological improvement and rational choices to buy efficiency to limit energy spending  (limited by the low price of fossil fuels and the absence of any cost for emitting CO2).

CO2 per unit of energy consumption depends mostly on the mix of fuels and energy sources. This is the subject of most current policy interventions such as RPS for electricity, CAFE fleet fuel economy mandates, policies to boost renewables while discouraging coal, trying to develop CO2 sequestration, etc. I don't have any numbers at hand on this factor. The west has been shifting away from coal a bit, but China is going all out for coal-fired electricity, and we may see both tar sands and coal-to-liquids grow rapidly (at high CO2 intensity) to fill the gap as conventional oil supply becomes tight (even if it just hits a long plateau and fails to keep up with big GDP growth).

What if there were no hypothetical situations?