Human-induced climate change is already happening. People - particularly poor people - struggle with its impacts every day. Whilst world leaders argue over how to tackle this immense issue, one thing must be agreed on now: the level of change the world needs to avoid. For millions, 'safe' levels of change have already been exceeded and international efforts must be
ramped up to support the affected communities. But above 2Ã‚Â°C the impacts will become progressively less manageable, perhaps uncontrollable. This paper explains why global average temperature rise must be kept as far below 2Ã‚Â°C as possible (from pre-industrial levels), based on a review of evidence of the impacts at different temperature ranges. It explains how impacts on water resources, food production and ecosystems become catastrophic above that threshold, and how dangerous feedback mechanisms are much more likely to kick in, resulting in even faster warming.