Abstract:The global surface temperature in 2021 was 1.11℃ (±0.13℃) higher than the pre-industrial level, being the seventh warmest year on record. Ocean heat content and global mean sea level have reached record highs, while the Antarctica and Arctic sea-ice extents were lower than normal. Many high-impact weather and climate events occurred across the world in 2021, including torrential rains and floods in Eurasia, severe droughts in North America and Asia, frequent tropical cyclones in the North Atlantic and North Indian Ocean, heatwaves and wildfires in Europe and North America, cold spells and snowstorms in Europe, America and Asia as well as severe convective weather events in many regions. Cause analyses suggest that in mid-July, central Europe was continuously controlled by the cut-off low pressure, and the water vapor from the Atlantic and Mediterranean was transported to central and western Europe, bringing extremely heavy precipitation and floods. In mid-February, the tropospheric polar vortex migrated southward from the Arctic to central North America, forming a stable low-pressure trough. Under the combined action of the low-pressure trough, favorable low-level water vapor transportation and the stratospheric sudden warming in the early stage, extreme low-temperatures and severe snowstorms attacked most regions of North America.