evidence: Once we surpass 2°C (which is internationally considered the "danger limit" beyond which we should not pass), the impacts listed above are exacerbated, and some new impacts will occur. Coastal flooding will impact millions of people. Coral bleaching will be widespread (exacerbated by ocean acidification), most coral reefs may not survive (Frieler et al. 2012, Kiessling et al. 2012), global food crop production will decline, and sea levels will rise by close to 1 meter by 2100. Up to 30% of global species will be at risk for extinction. [...] For further details, see our post here and the Point of No Return report (pages 23–25) by Ecofys and Greenpeace. To summarize, we do not want to exceed 2°C warming above pre-industrial levels (even that amount of warming is very risky), and 3–4°C or more puts us at serious risk of catastrophic climate change. Now let's examine when we can expect to reach these temperatures in various climate sensitivity and greenhouse gas emissions scenarios.