Anthropogenic activities have substantially enhanced the loadings of reactive nitrogen (Nr) in the Earth system since pre-industrial times^1,2, contributing to widespread eutrophication and air pollution^3,4,5,6. Increased Nr can also influence global climate through a variety of effects on atmospheric and land processes but the cumulative net climate effect is yet to be unravelled. Here we show that anthropogenic Nr causes a net negative direct radiative forcing of −0.34 [−0.20, −0.50] W m⁻² in the year 2019 relative to the year 1850. This net cooling effect is the result of increased aerosol loading, reduced methane lifetime and increased terrestrial carbon sequestration associated with increases in anthropogenic Nr, which are not offset by the warming effects of enhanced atmospheric nitrous oxide and ozone. Future predictions using three representative scenarios show that this cooling effect may be weakened primarily as a result of reduced aerosol loading and increased lifetime of methane, whereas in particular N₂O-induced warming will probably continue to increase under all scenarios. Our results indicate that future reductions in anthropogenic Nr to achieve environmental protection goals need to be accompanied by enhanced efforts to reduce anthropogenic greenhouse gas emissions to achieve climate change mitigation in line with the Paris Agreement.

自工业化前时期以来，人类活动大大增加了地球系统中活性氮（Nr）的含量^1,2 ，导致广泛的富营养化和空气污染^3,4,5,6 。 Nr 的增加还可以通过对大气和陆地过程的各种影响来影响全球气候，但累积的净气候影响尚未阐明。在这里，我们表明，相对于 1850 年，人为 Nr 在 2019 年造成净负直接辐射强迫为 −0.34 [−0.20, −0.50] W m ^−2。这种净冷却效应是气溶胶负荷增加、减少的结果。甲烷寿命和与人为 Nr 增加相关的陆地碳封存增加，但大气中一氧化二氮和臭氧增加的变暖效应并不能抵消这些影响。使用三种代表性情景的未来预测表明，这种冷却效应可能会减弱，主要是由于气溶胶负荷减少和甲烷寿命增加，而特别是 N ₂ O 引起的变暖在所有情景下可能会继续增加。我们的研究结果表明，未来为了实现环境保护目标而减少人为氮氧化物，需要同时加大力度减少人为温室气体排放，以根据《巴黎协定》减缓气候变化。