This chapter, "Detection and Attribution of Climate Change: from Global to Regional," is part of the IPCC's Fifth Assessment Report on Climate Change. It assesses the causes of observed changes in climate, using physical understanding, climate models, and statistical approaches. The chapter highlights that more than half of the observed increase in global mean surface temperature (GMST) from 1951 to 2010 is likely due to anthropogenic greenhouse gas (GHG) concentrations. The consistent changes across the climate system, including warming of the atmosphere and ocean, sea level rise, ocean acidification, changes in the water cycle, the cryosphere, and climate extremes, point to a large-scale warming primarily driven by GHG increases. Solar forcing is the only known natural forcing contributing to warming but has increased much less than GHG forcing. The chapter also discusses the detection and attribution of anthropogenic influence on temperature changes in different regions, ocean temperatures, sea level rise, ocean acidification, oxygen changes, the water cycle, the cryosphere, and climate extremes. It emphasizes the robust evidence from multiple studies using different methods and the improved understanding of observational uncertainties and model simulations. The chapter concludes that human influence has been detected in major components of the climate system, and the combined evidence increases the confidence in the attribution of observed climate change.This chapter, "Detection and Attribution of Climate Change: from Global to Regional," is part of the IPCC's Fifth Assessment Report on Climate Change. It assesses the causes of observed changes in climate, using physical understanding, climate models, and statistical approaches. The chapter highlights that more than half of the observed increase in global mean surface temperature (GMST) from 1951 to 2010 is likely due to anthropogenic greenhouse gas (GHG) concentrations. The consistent changes across the climate system, including warming of the atmosphere and ocean, sea level rise, ocean acidification, changes in the water cycle, the cryosphere, and climate extremes, point to a large-scale warming primarily driven by GHG increases. Solar forcing is the only known natural forcing contributing to warming but has increased much less than GHG forcing. The chapter also discusses the detection and attribution of anthropogenic influence on temperature changes in different regions, ocean temperatures, sea level rise, ocean acidification, oxygen changes, the water cycle, the cryosphere, and climate extremes. It emphasizes the robust evidence from multiple studies using different methods and the improved understanding of observational uncertainties and model simulations. The chapter concludes that human influence has been detected in major components of the climate system, and the combined evidence increases the confidence in the attribution of observed climate change.