I think you missed my meaning. Blow up means runaway warming or cooling. Neither has happened in the Earth's 4.5 billion year history. One must therefore conclude that the Earth's climate is not dominated by positive feedback.
Your comment about positive feedback loops makes sense in the absolute but I think it's a bit more complicated. With climate you have lots of different cycles all operating on different time scales. While a positive feedback loop (like loss of snow albedo leading to more warming) may dominate for a while, it may eventually be overturned by another cycle, such as long term changes in the orbit of the earth around the sun (Milankovich cycles) which would eventually act to cool the earth back down.
But we need to be concerned with the short term effects, and most science suggests that these are going to hammer us in the near term (the next decades and possibly centuries).