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Abstract Many agricultural regions in China are likely to become appreciably wetter or drier as the global climate warming increases. However, the impact of these climate change patterns on the intensity of soil greenhouse gas (GHG) emissions (GHGI, GHG emissions per unit of crop yield) has not yet been rigorously assessed. By integrating an improved agricultural ecosystem model and a meta‐analysis of multiple field studies, we found that climate change is expected to cause a 20.0% crop yield loss, while stimulating soil GHG emissions by 12.2% between 2061 and 2090 in China's agricultural regions. A wetter‐warmer (WW) climate would adversely impact crop yield on an equal basis and lead to a 1.8‐fold‐ increase in GHG emissions relative to those in a drier‐warmer (DW) climate. Without water limitation/excess, extreme heat (an increase of more than 1.5°C in average temperature) during the growing season would amplify 15.7% more yield while simultaneously elevating GHG emissions by 42.5% compared to an increase of below 1.5°C. However, when coupled with extreme drought, it would aggravate crop yield loss by 61.8% without reducing the corresponding GHG emissions. Furthermore, the emission intensity in an extreme WW climate would increase by 22.6% compared to an extreme DW climate. Under this intense WW climate, the use of nitrogen fertilizer would lead to a 37.9% increase in soil GHG emissions without necessarily gaining a corresponding yield advantage compared to a DW climate. These findings suggest that the threat of a wetter‐warmer world to efforts to reduce GHG emissions intensity may be as great as or even greater than that of a drier‐warmer world. 

Abstract. Excessive anthropogenic nitrogen (N) inputs to the biosphere have disruptedthe global nitrogen cycle. To better quantify the spatial and temporalpatterns of anthropogenic N inputs, assess their impacts on thebiogeochemical cycles of the planet and the living organisms, and improvenitrogen use efficiency (NUE) for sustainable development, we have developeda comprehensive and synthetic dataset for reconstructing the History ofanthropogenic Nitrogen inputs (HaNi) to the terrestrial biosphere. The HaNi datasettakes advantage of different data sources in a spatiotemporally consistentway to generate a set of high-resolution gridded N input products from thepreindustrial period to the present (1860–2019). The HaNi dataset includes annual ratesof synthetic N fertilizer, manure application/deposition, and atmospheric Ndeposition on cropland, pasture, and rangeland at a spatial resolution of5 arcmin × 5 arcmin. Specifically, the N inputs are categorized, according to the Nforms and land uses, into 10 types: (1) NH4+-N fertilizer applied to cropland,(2) NO3--N fertilizer applied to cropland, (3) NH4+-N fertilizer applied to pasture,(4) NO3--N fertilizer applied to pasture, (5) manure N application oncropland, (6) manure N application on pasture, (7) manure N deposition onpasture, (8) manure N deposition on rangeland, (9) NHx-N deposition, and(10) NOy-N deposition. The total anthropogenic N (TN) inputs to globalterrestrial ecosystems increased from 29.05 Tg N yr−1 in the 1860s to267.23 Tg N yr−1 in the 2010s, with the dominant N source changing fromatmospheric N deposition (before the 1900s) to manure N (in the 1910s–2000s)and then to synthetic fertilizer in the 2010s. The proportion of syntheticNH4+-N in fertilizer input increased from 64 %in the 1960s to 90 % in the 2010s, while synthetic NO3--N fertilizerdecreased from 36 % in the 1960s to 10 % in the 2010s. Hotspots of TNinputs shifted from Europe and North America to East and South Asia duringthe 1960s–2010s. Such spatial and temporal dynamics captured by the HaNidataset are expected to facilitate a comprehensive assessment of the coupledhuman–Earth system and address a variety of social welfare issues, such as theclimate–biosphere feedback, air pollution, water quality, and biodiversity. Thedata are available at https://doi.org/10.1594/PANGAEA.942069(Tian et al., 2022). 

Abstract. Nitrous oxide (N2O) is a long-lived potent greenhouse gas and stratospheric ozone-depleting substance that has been accumulating in the atmosphere since the preindustrial period. The mole fraction of atmospheric N2O has increased by nearly 25 % from 270 ppb (parts per billion) in 1750 to 336 ppb in 2022, with the fastest annual growth rate since 1980 of more than 1.3 ppb yr−1 in both 2020 and 2021. According to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR6), the relative contribution of N2O to the total enhanced effective radiative forcing of greenhouse gases was 6.4 % for 1750–2022. As a core component of our global greenhouse gas assessments coordinated by the Global Carbon Project (GCP), our global N2O budget incorporates both natural and anthropogenic sources and sinks and accounts for the interactions between nitrogen additions and the biogeochemical processes that control N2O emissions. We use bottom-up (BU: inventory, statistical extrapolation of flux measurements, and process-based land and ocean modeling) and top-down (TD: atmospheric measurement-based inversion) approaches. We provide a comprehensive quantification of global N2O sources and sinks in 21 natural and anthropogenic categories in 18 regions between 1980 and 2020. We estimate that total annual anthropogenic N2O emissions have increased 40 % (or 1.9 Tg N yr−1) in the past 4 decades (1980–2020). Direct agricultural emissions in 2020 (3.9 Tg N yr−1, best estimate) represent the large majority of anthropogenic emissions, followed by other direct anthropogenic sources, including fossil fuel and industry, waste and wastewater, and biomass burning (2.1 Tg N yr−1), and indirect anthropogenic sources (1.3 Tg N yr−1) . For the year 2020, our best estimate of total BU emissions for natural and anthropogenic sources was 18.5 (lower–upper bounds: 10.6–27.0) Tg N yr−1, close to our TD estimate of 17.0 (16.6–17.4) Tg N yr−1. For the 2010–2019 period, the annual BU decadal-average emissions for both natural and anthropogenic sources were 18.2 (10.6–25.9) Tg N yr−1 and TD emissions were 17.4 (15.8–19.20) Tg N yr−1. The once top emitter Europe has reduced its emissions by 31 % since the 1980s, while those of emerging economies have grown, making China the top emitter since the 2010s. The observed atmospheric N2O concentrations in recent years have exceeded projected levels under all scenarios in the Coupled Model Intercomparison Project Phase 6 (CMIP6), underscoring the importance of reducing anthropogenic N2O emissions. To evaluate mitigation efforts and contribute to the Global Stocktake of the United Nations Framework Convention on Climate Change, we propose the establishment of a global network for monitoring and modeling N2O from the surface through to the stratosphere. The data presented in this work can be downloaded from https://doi.org/10.18160/RQ8P-2Z4R (Tian et al., 2023).