So the question whether man - made warming will be catastrophic depends on the assumption of strong net positive feedbacks in the climate system. (climate-skeptic.com)
We don't deny warming or greenhouse gas theory, we deny the catastrophe, which we face only if the assumption of the climate being dominated by strong net positive feedback is correct. (fakegate.org)
This second theory of strongly net positive feedback in climate is poorly proven, and in fact evidence exists the sign may not even be positive. (climate-skeptic.com)