Many emerging climate change risks are concentrated in urban areas. Urban areas hold more than half the world’s population and most of its built assets and economic activities. They also house a large proportion of the population and economic activities most at risk from climate change.Climate change impacts on cities are increasing. Key issues include rising temperatures, heat stress, water security and pollution, sea-level rise and storm surges, extreme weather events, heavy rainfall and strong winds, inland flooding, food security, and ocean acidification. By 2050, the global urban population is expected to have increased by 2.5–3 billion relative to 2009, corresponding to 64–69% of the world population. Urban areas are a key driver of greenhouse gas (GHG) emissions across multiple sectors and currently account for over 70% of global energy use.