State of the Global Climate 2021

This report provides an update on the observed state of the global climate in 2021 and documents continuing trends in key climate indicators previously highlighted in major scientific assessments. It examines changes in atmospheric composition, including concentrations of greenhouse gases, as well as variations in global annual mean surface temperature, global mean sea level, ocean heat content and ocean acidification. The report also assesses cryospheric indicators such as sea-ice extent and changes in the mass of ice sheets and glaciers. Together, these indicators show that the climate system continues to undergo measurable and persistent change. In addition to physical climate observations, the report reviews the socioeconomic consequences of weather and climate extremes during the year. It highlights the growing vulnerability of populations to climate-related hazards, noting that high-impact events caused economic losses exceeding one hundred billion United States dollars and produced significant disruptions to food security and humanitarian conditions across multiple regions.