This is one of two technical background papers prepared as a basis for discussion at the WHO Health and Climate Conference. It provides a brief summary of the available evidence on the health impacts of climate change, and an outline of the necessary response to protect health from these evolving risks. Specifically, it considers the need for overall strengthening of the health system, specific functions both within and outside the health sector that require strengthening and modification to address climate risks, and introduces some of the main areas and opportunities for future progress.