Don S Im pretty sure the idea of runaway positive feedback in the global warming context goes back to Hansen in the s and the beginning of the whole movement after the previous new ice age movement of course His specialty was Venus and its unique atmospheric dynamics Somehow he became convinced that the same would happen to Earth even though the necessary vulcanism proximity to the sun lack of a biosphere and water cycle and atmospheric composition are all totally nonEarth like But he is convinced well turn Earth into a new Venus even though we cant and the fact that his projections are failing badly means that his acolytes and people not even aware of where this crap came from are now inventing nonphysical tipping points at unknown times in the near future to justify continuing panic The fact that Hansen engineered a hot unairconditioned room back in his original testimony to your politicians is a testament to the fact he is not really much of a scientistnnOf course in engineering and real systems positive feedback is ultimately limited by saturation somewhere in the system but they dont seem to identify what will saturate first in the climate system