Human interference with the climate system is rapidly taking us into uncharted territory, with the potential for severe and irreversible impacts and making it harder to achieve the Sustainable Development Goals (SDGs). The Paris Agreement aims to limit average global warming to well below 2°C, a political judgement based on scientific evidence. The stringency of this mitigation goal means that countries need to strengthen mitigation action without delay. After setting out the case for urgent action and the carbon budget consistent with the goal of well below 2°C, this chapter examines the characteristics of low-emission pathways and how country diversity may impact the scale, phasing and priorities for mitigation action across countries. It then summarises projected impacts, emphasising the need for flexible, forward-looking approaches to decision-making that reflect the diversity of climate vulnerabilities and confidence levels about local and regional change. Finally, the chapter looks at how countries can get to where they need to be, supported by the mechanisms of the Paris Agreement.