What Virtue In False Promises?

One of the things that strikes me repeatedly watching the global warming debate (especially in the lead-up to and in the wake of the Copenhagen conference) is the incredible amount of excitement people have about trying to get countries to make commitments in regards to CO2 emissions which they obviously are not going to keep.

For instance, in discussing their hopes for Copenhagen, a number of environmentalists expressed hope that there would not be another "do nothing" commitment such as the Kyoto Accord -- despite the fact that even those countries which did agree to Kyoto had not managed to keep those very modest commitments. The goals that environmentalists did very much want to see committed to (generally a 80-90% global drop in CO2 emissions within somewhere between 10 and 40 years) are far more aggressive, and thus far more unrealistic.

This struck me in particular when I stumbled across this advocacy piece, in which the author expresses hope that leaders of nations will commit to decreasing CO2 emissions by 80% in ten years (by 2020) and as a first step urges people to take the radical step of decreasing their "carbon footprints" by 25%. If committed environmentalists are only finding ways to decrease their household CO2 emissions by 25%, how in the world do they expect a whole country to drop its emissions by 80%?

Environmentalists have widely branded the Copenhagen summit as a failure because it didn't produce a firm commitment to massive CO2 emission reductions within a couple decades. Even beloved left-of-center leaders such as President Obama have been branded by their own base as "irresponsible" for not making strong commitments at Copenhagen. But if there simply does not seem to be a way to achieve such reductions, if even activists willing to significantly change their lifestyles in order to reduce their personal "carbon footprints" are not able to reliably achieve such drastic reductions in the short term, I fail to understand how it was "irresponsible" of Obama, Sarkozy, etc. to refuse to commit to doing something they frankly have no idea of how to do.

Wouldn't it be irresponsible to make a commitment you have no idea how to keep?