Climate change resulting from emissions of CO2 and other greenhouse gases (GHGs) is widely regarded to be the greatest environmental challenge facing the world today. It also represents one of the greatest social and economic threats facing the planet and the welfare of humankind. The focus of climate change mitigation policy to date has been on "preventing dangerous anthropogenic interference with Earth's climate system". There is no global agreement or scientific consensus for delineating ‘dangerous’ from ‘acceptable’ climate change but limiting global average temperature rise to 2 °C above pre-industrial levels has emerged as a focus for international and national policymakers. The origin and selection of this 2 °C policy threshold is not entirely clear but its determination has been largely informed by assessments of impacts at different levels of temperature increase such as those of the UNFCCC Assessment Report 4 (AR4). With few exceptions, such assessments tend to present a gradual and smooth increase in scale and severity of impacts with increasing temperature. The reality, however, is that climate change is unlikely to be a smooth transition into the future and that there are a number of thresholds along the way that are likely to result in significant step changes in the level of impacts once triggered. The existence of such thresholds or ‘tipping points’ is currently not well reflected in mitigation or adaptation policy and this oversight has profound implications for people and the environment. The phrase ‘tipping point’ captures the intuitive notion that “a small change can make a big difference” for some systems (1). In addition, the term ‘tipping element’ has been introduced to describe those large-scale components of the Earth system that could be forced past a ‘tipping point’ and would then undergo a transition to a quite different state. In its general form, the definition of tipping points may be applied to any time in Earth history (or future) and might apply to a number of candidate tipping elements. However, from the perspective of climate policy and this report we are most concerned with ‘policy-relevant’ tipping elements which might be triggered by human activities in the near future and would lead to significant societal impacts within this century. Considering both the conditions for and likelihood of tipping a number of different elements, the report focuses on the following subset of phenomena and regions where passing tipping points might be expected to cause significant impacts within the first half of this century. Impacts have been explored and assessed in as much detail as possible within such a short study paying particular attention to economic costs and implications for the insurance sector (further information is contained in the main text of the report).