We using a combination of continuous 60-year meteorological and 6-year tower-based carbon dioxide (CO₂) flux measurements constructed a clear picture of a HWs effect.

HWs, as an extreme weather event, have increased during last two decades in the Songnen meadow steppe.

HWs will reduce the carbon flux of the steppe and will cause a sustained impact.

Drought may be the main reason why HWs decrease carbon flux.