Increasing worldwide demand for beef products promotes international beef trade. Cattle raising and beef products as significant sources of methane (CH 4 ) emissions have received widespread concerns. However, the factors driving CH 4 emissions embodied in the global beef trade have not been quantified. Here, we evaluate international beef trade-induced CH 4 emissions and assess the contribution of the five driving factors to changes in CH 4 emissions embodied in the beef trade from 2000 to 2018. We show that driven by increasing population and meat demands, the global beef trade-induced CH 4 emissions increased continuously in the past two decades, with total emissions of 9337.3 Gg in 2018. The drivers that could potentially reduce trade-related emissions are emission intensities in beef exporting countries and beef importing countries' selections of their beef suppliers. Together, these two driving factors reduced CH 4 emissions by 923.5 Gg from 2012 to 2018. Results suggest that efforts should be made to reduce the emission intensity via improving cattle feed and feeding practices in beef exporting countries. Beef importing countries could also contribute to CH 4 emission reduction by selecting those beef exporting countries with low emission intensities.

No abstract

Radiative forcing (RF) quantifies how human activities and natural factors perturb the energy balance and flow of the climate system (Andrews & Forster, 2020;Ramanathan, 1975). It is often used to characterize the degree of contribution of greenhouse gases, aerosols, clouds, and land cover change to climate (Bellouin et al., 2019;. A primary effect of RF on climate change is through temperature feedback, with positive forcing leading to warming and negative forcing leading to cooling (Sherwood et al., 2015). Of those significant climate forcers contributing to RF, land-use/land-cover change (LULCC) has been a global concern due to its significant influence on the carbon balance between terrestrial ecosystems and the atmosphere and carbon emission (

No abstract

Abstract. Associations between tropospheric ozone (O3) and climate variations have been extensively investigated worldwide. However, given the lack of historical O3 monitoring data, the knowledge gaps regarding the influences of climate variations on long-term O3 trends in China remain. The present study used a unique tropospheric O3 dataset from the summer of 1999 to 2017 simulated by an atmospheric chemistry model to explore the linkage between summer O3 and a dominant atmospheric circulation system – the Western Pacific Subtropical High Pressure (WPSH) on an interannual basis in China. During this period, both WPSH strength and O3 concentrations in eastern and central China illustrated a growing trend. An EOF analysis was conducted to examine significant summer O3 characteristics and patterns and their potential connections with the WPSH. We show that the WPSH determines interannual fluctuations of summer O3, whereas O3 precursor emissions contribute primarily to the O3 long-term trend. Special efforts were made to discern the associations of O3 variations in major urban agglomerations of China and the WPSH. The results reveal that the WPSH plays a more vital role in O3 perturbation in the eastern seaboard regions and inland China, but leads to lower O3 levels in the Pearl River Delta (PRD) region. Precursor emissions made more significant contributions up to 60 % to increasing O3 trends in the inland urban agglomerations than coastal regions in eastern and southern China. The strongest contribution of meteorological conditions associated with the WPSH to summer ozone concentration occurred in the Yangtze River Delta (YRD), accounting for over 9 % to ozone perturbations from 1999 to 2017. Overall, we find that the effect of the WPSH on regional O3 depends on the spatial proximity to the WPSH. We attributed the effects of the WPSH on O3 interannual variations to the changes in air temperature, precipitation, and winds associated with the WPSH’s intensity and positions.