Human activities have caused considerable perturbations of the nitrogen (N) cycle, leading to a ~20% increase in the concentration of atmospheric nitrous oxide (N₂O) since the preindustrial era. While substantial efforts have been made to quantify global and regional N₂O emissions from cropland, there is large uncertainty regarding how climate change and variability have altered net N₂O fluxes at annual and decadal time scales. Herein, we applied a process‐based dynamic land ecosystem model (DLEM) to estimate global N₂O emissions from cropland driven by synthetic N fertilizer application and multiple environmental factors (i.e., elevated CO₂, atmospheric N deposition, and climate change). We estimate that global cropland N₂O emissions increased by 180% (from 1.1 ± 0.2 to 3.3 ± 0.1 Tg N year⁻¹; mean ±1 standard deviation) during 1961–2014. Synthetic N fertilizer applications accounted for ~70% of total emissions during 2000–2014. At the regional scale, Europe and North America were two leading regions for N₂O emissions in the 1960s. However, East Asia became the largest emitter after the 1990s. Compared with estimates based on linear and nonlinear emission factors, our results were 150% and 186% larger, respectively, at the global scale during 2000–2014. Our higher estimates of N₂O emissions could be attributable to the legacy effect from previous N addition to cropland as well as the interactive effect of N addition and climate change. To reduce future cropland N₂O emissions, effective mitigation strategies should be implemented in regions that have received high levels of N fertilizer and regions that would be more vulnerable to future climate change.

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氮和环境因素驱动的全球农田N2O排放：比较和不确定性分析

自从工业化时代以来，人类的活动已经引起了氮（N）循环的极大扰动，导致大气中的一氧化二氮（N ₂ O）浓度增加了约20％。尽管已经做出了巨大的努力来量化农田的全球和区域N ₂ O排放量，但是在每年和十年的时间尺度上，气候变化和可变性如何改变了净N ₂ O通量仍存在很大的不确定性。本文中，我们应用了基于过程的动态土地生态系统模型（DLEM），以估算由合成氮肥施用和多种环境因素（例如，CO ₂升高）驱动的农田中的全球N ₂ O排放，大气氮沉降和气候变化）。我们估计，1961-2014年期间，全球农田N ₂ O排放增加了180％（从1.1±0.2到3.3±0.1 Tg N年^-1；平均±1标准偏差）。在2000-2014年期间，合成氮肥的使用量约占总排放量的70％。在区域范围内，欧洲和北美是1960年代N ₂ O排放的两个主要区域。但是，东亚成为1990年代后的最大排放国。与基于线性和非线性排放因子的估计相比，我们的结果在2000-2014年全球范围内分别增加了150％和186％。我们对N _2的更高估计O排放可能归因于先前氮素对农田的遗留效应以及氮素与气候变化的相互作用。为了减少未来农田的N ₂ O排放，应在氮肥水平较高的地区和更容易受到未来气候变化影响的地区实施有效的缓解策略。