That is what I mean too, but "sudden" when speaking of climate change can be any thing between 50 and 1000 years and "runaway change" means a three sigma difference from common historical records of one sigma statistical variation. I am not predicting mankind's extinction by 2030 as Guy McPherson* is, but have said I think it possible that my grand child, nearly 17 years old, and starting to think about where he would like to go to college after one more year of high school MAY not ever be in my position, taking pleasure in the fact he has already been to Cornell, where his parents met and I started my undergraduate work some 30+ years earlier. I'll convert that to years for you: He is unlikely to have any child before 37 years old if he too goes to grad school. That child likewise will not have his grand child until 20+ 35= 55 years from now. That grand child, if very bright, might be starting to think about where to go to college when 15. So I saying that the serious shit could start to hit the fan in 70 years from now, and that is certainly "sudden" on human times scales and unfortunately very plausible as the increases of temperature and humidity are accelerating via more than a dozen major mutually amplifying GW interactions now. * Google: "Nature Bats Last" for many articles of his and link to his site where many agree and mainly discuss how we should spend our remaing 2.5 decades. I have 3 or so posts there as Billy T in which I basically tell that switching all cars to sugar cane alcohol in a decade is possible, and at least would delay the inevitable end they ALL expect. I point out that doing so is a good idea anyway as sugar cane alcohol is cheaper per mile driven than gasoline, without any subsidy, (No "depletions allowance," or other tax breaks that Big Oil gets) and gives slightly more power to your motor, is possibly the only economically feasible way to remove some carbon (in CO2) from the air and keep it safely in large storage tanks at filling stations and in at least 100 million car fuel tanks; cleaner burning so lower tune-up and repair bills plus the spark plugs last longer, etc. - I have no evidence I have made any converts there. - Big Oil has them steadfast fatalist and they don't even seem angry as I am about big oil is ripping us off financially and spreading lies that switching ALL cars to alcohol cannot be done and even if it could, that would kill all the rain forests etc.