From "Irreversible Does Not Mean Unavoidable," by H. Damon Matthews
and Susan Solomon, _Science_ 26 April 2013, p. 438:
"The notion that there will be additional future warming
or "warming in the pipeline" if the atmospheric concentrations of carbon
dioxide were to remain fixed at current levels has been misinterpreted
to mean that the rate of increase in Earth's global temperature is
inevitable, regardless of how much or how quickly emissions decrease.
Further misunderstanding may stem from recent studies showing that the
warming that has already occurred as a result of past anthropogenic
carbon dioxide increases is irreversible on a time scale of at least
1000 years. But irreversibility of past changes does not mean that
further warming is unavoidable. . . .
"If emissions were to cease abruptly, global average
temperatures would remain roughly constant for many centuries, but they
would not increase very much, if at all. . . . any further increase in
CO2-induced warming is entirely the result of current CO2 emissions. . .
"Societal inertia, rather than the inertia of the climate
system, is thus the critical challenge if we wish to begin to decrease
the rate of CO2-induced global warming in the near future. . . .
"Climate warming tomorrow, this year, this decade, or this
century is not predetermined by past CO2 emissions; it is yet to be
determined by future emissions. The climate benefits of emissions
reductions would thus occur on the same time scale as the political
decisions that lead to the reductions."
The key phrase in the above is SOCIETAL INERTIA. Really dropping CO2 emissions--making them "cease abruptly"--is not going to be accomplished with a few more regulations here and there, as will be the only likely outcome of Obama's speech. The whole huge, bloated scale of the global economy needs to be dramatically reduced, and for that to happen the patterns of human social organization will have to change. Speaking of "a combination of aggressive mitigation combined with massive spending" on ways to "adapt" is basically a way of acquiescing to a continuation of business as usual, and to vainly hope that Miami, or other low-lying cities around the world, can survive the century "intact" displays a woeful inability to envision the finitude of a planet already inhabited by more than 7 billion people, most of them living in shockingly unsustainable ways. Most people would probably agree, confronted with the basics of our human situation and thinking "rationally," that a deep change in our social reality would be "good for us" (turning off the burner that's frying the planet is just one reason why), but the inertia in the old system, the vast net of expectations we all carry around in our heads that has such a hold on us, is difficult to overcome. Starting to talk about the problem at this level is at least a first step toward bringing it about, in my opinion.