This paper looks at the potential impacts of climate change on migration and forced displacement, and the implications for humanitarian responses. It notes how diverse patterns of mobility, migration and displacement are the norm in most countries affected by chronic or recurrent humanitarian crises. The most negative human impacts of climate change are likely to result in episodes of sudden and large-scale forced migration. Many fragile states already fail to provide adequate social protection to poor and vulnerable populations, so any climate-related deterioration in human welfare has the potential to generate humanitarian needs that are far beyond the capacities or willingness of these states to address. It is in these contexts that international humanitarian responses are likely to prove most critical. Here, superficial climate change adaptation and disaster risk reduction efforts may do little to address the root causes of vulnerability. Greater priority needs to be given to ensuring flexible humanitarian funding and programming in countries where the effects of climate change are likely to be felt most directly, and where these are likely to be exacerbated by population growth, economic stagnation, conflict, urbanization or environmental stress.