Well, the scary stuff is the evidence in polar ice cores that have shown that things like ocean currents can stop and reverse with temperature shifts, amplifying the effect, so there have been examples where ice ages can come on in just a matter of 6-7 years.
Climate change may be more insidious though -- kind of like the problems in Italian soccer. Corrosive, but they take a little time. First it starts out with the Netherlands and Venice under water. Within a few years, more hurricanes, drought, and famines. Then civil wars, riots, starving people, and more political unrest.
Before you know it, you look back 15 years and you realize it was once unthinkable to eat your neighbor as a food source.