Climate change is now very much with us, and for the poorest of the poor the implications are particularly daunting. These often remote or marginalised communities are so burdened they will struggle to meet the coming challenges. Adaptation - learning to cope with rising temperature and other effects of climate change - is a difficult but essential task for these vulnerable millions. This briefing paper defines climate change adaptation and shows why it matters, who needs to adapt most, and what shape adaptation must take across a range of scales and sectors.