Signal Radiative forcing at +3.10 W/m2, three times the boundary

Summary

Total human-caused radiative forcing at the top of the atmosphere reaches +3.10 W/m2 in the 2026 assessment, more than three times the +1 W/m2 boundary and above the +2.91 W/m2 of the 2023 assessment. The indicator sums every human influence on Earth's energy balance, including carbon dioxide, methane, nitrous oxide, aerosols and land-use change, to express the overall strength of human-driven climate change. Forcing was fairly stable during the pre-industrial Holocene, and marked positive forcing began with the Industrial Revolution as fossil fuel use and land conversion grew. The +1 W/m2 boundary rests on climate sensitivity, the response of polar ice sheets to warming and evidence of instability above +1.5 W/m2, which serves as the high-risk line. Satellites can measure top-of-atmosphere fluxes, but estimating the human share depends on climate models. The report sees the current value as exerting a persistent warming push on the Earth system.