Hermann Held

TL;DR: Work in different scientific fields is now suggesting the existence of generic early-warning signals that may indicate for a wide class of systems if a critical threshold is approaching.

TL;DR: It is explained how, in principle, early warning systems could be established to detect the proximity of some tipping points, and critically evaluate potential policy-relevant tipping elements in the climate system under anthropogenic forcing.

TL;DR: This work analyzes eight ancient abrupt climate shifts and shows that they were all preceded by a characteristic slowing down of the fluctuations starting well before the actual shift, implying independent empirical evidence for the idea that past abrupt shifts were associated with the passing of critical thresholds.

TL;DR: These guidance notes are intended to assist the Lead Authors of the Fifth Assessment Report (AR5) in the consistent treatment of uncertainties across all three Working Groups as discussed by the authors, which can be used broadly for developing expert judgments and for evaluating and communicating the degree of certainty in findings of the assessment process.

TL;DR: It is deduced conservative lower bounds for the probability of triggering at least 1 of those events of 0.16 for medium (2–4 °C), and 0.56 for high global mean temperature change (above 4 °C) relative to year 2000 levels.