A representative CO_(2) emissions pathway for China toward carbon neutrality under the Paris Agreement's 2℃target

In 2021,China updated its nationally determined contributions(NDCs)under the Paris Agreement,which prompts a more accurate mea-surement of its emissions inventory and a reasonable pathway toward carbon neutrality by 2060.This study reviews the estimates using the bottom-up emissions factor method or the top-down atmospheric CO_(2) concentration inversion method to derive China's CO_(2) emissions inventory and finds that CO_(2) emissions from energy combustion and industrial processes in Chinese mainland range from 11.3-12.0 GtCO_(2) in 2021.Based on a comprehensive review of pathways proposed by domestic and international studies and an analysis of the origins of their differences,we proposed the Tsinghua-CMA pathway that coordinates the 2℃global temperature rise control target with China's current CO_(2) emissions status and mitigation policies.The pathway requires China's CO_(2) emissions to peak around 2028-2029 at about 12.8 GtCO_(2),then decline steadily to about 11.2 GtCO_(2) in 2035,3.6 GtCO_(2) in 2050,and 0.9 GtCO_(2) in 2060.Compared to a reference scenario without updated NDCs,this pathway would result in an economic cost of about 0.9%cumulative GDP between 2020 and 2060,only 1/4-1/3 of the cost associated with pathways that align with the 1.5℃target.We recommended that China improves emissions accounting by cross-validating bottom-up and top-down approaches and regularly updating the pathway toward carbon neutrality while maintaining consistency with its evolving CO_(2) emissions inventory,policy trends,and global CO_(2) emission budget updates.

Adding the impacts of biological crusts on sand and dust storm emission in Asia

Although biological crusts(biocrusts)grant stability to dust source areas by inhibiting dust emission,only a few models have explicitly considered their inhibitory effect.In this study,we used the China Meteorological Administration Unified Atmospheric Chemistry Environment/Dust model and combined retrieved biocrust information with two biocrust inhibition schemes(roughness length and biocrust strength schemes)to study numerically the inhibitory effect of biocrusts on a strong dust storm that occurred in Central and East Asia on 25−30 Mar.2018.The inhibitory effect of biocrusts on dust emission increased with biocrust coverage.The total dust emission forecasted by the roughness length and biocrust strength schemes was reduced by approximately 56.7%and 47.9%on average,respectively.In downstream sites in China,the surface mass concentrations of PM10 forecasted by the roughness length and biocrust strength schemes decreased by 36%–57%and 24%–41%,respectively.When biocrusts were considered,the forecast for stations near the dust source area considerably improved and that for stations distant from the source area became more reasonable but with larger bias under the combined effects of emission,transport and deposition.

An inversion model based on GEOS-Chem for estimating global and China's terrestrial carbon fluxes in 2019

The 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories added the method of assimilating atmospheric CO_(2) concentrations to invert carbon sources and sinks;however,many global carbon inversion models are not publicly available.In addition,our regional assimilation inversion system,CCMVS-R(China Carbon Monitoring,Verification and Supporting for Regional),needs a global carbon inversion model with higher assimilation efficiency to provide boundary conditions.Here,an inversion model based on the global atmospheric chemistry model GEOS-Chem and a more accurate and easier-to-implement ensemble square root Kalman filter(EnSRF)algorithm is constructed and used to infer global and China's carbon fluxes in 2019.Atmospheric CO_(2) concentrations from ObsPack sites and five additional CO_(2) observational sites from China's Greenhouse Gas Observation Network(CGHGNET)were used for data assimilation to improve the estimate.The inverted annual global terrestrial and oceanic carbon uptake is 2.12 and 2.53 Pg C per year,respectively,accounting for 21.1%and 25.1%of global fossil fuel CO_(2) emissions.The remaining 5.41 Pg C per year in the atmosphere is consistent with the global atmospheric CO_(2) growth rates of 5.44 Pg C per year reported by the National Oceanic and Atmospheric Administration(NOAA),showing that the inversion model can provide a reasonable estimate of global-scale natural carbon sinks.The inverted terrestrial carbon sink of China is 0.37 Pg C per year,accounting for approximately 13%of China's fossil CO_(2) emissions.

Differences in East Asian summer monsoon responses to Asian aerosol forcing under different emission inventories

Opposite anthropogenic aerosol emission trends in Asia can lead to different responses of the climate.Here,we examined the responses of the East Asian summer monsoon(EASM)to changes in Asian anthropogenic aerosol emissions during 2006-2014 using a global aerosol/atmospheric chemistry-climate coupled model(BCC_AGCM2.0_CUACE/Aero)with two sets of emission inventories:the Community Emissions Data System(CEDS)inventory adopted by the Coupled Model Intercomparison Project Phase 6(CMIP6)and the inventory developed at Peking University(PKU).The changes in Asian anthropogenic aerosol emissions during 2006-2014 between the two inventories were remarkably different,particularly in eastern China where completely opposite trends were observed(i.e.,increase in the CEDS inventory,but significant reduction in the PKU inventory).The perturbation simulations with the Asian anthropogenic aerosol forcing from the two inventories showed opposite changes in aerosol optical depth,aerosol effective radiative forcing,cloud liquid water path,and total cloud cover in eastern China.The simulated‘dipole-type’changes(i.e.,increase in India but decrease in China)in Asian aerosols and the resulting changes in local radiation budget under the PKU inventory were consistent with the corresponding observations.The summer surface temperatures over eastern China decreased by 0-0.4 K because of the Asian anthropogenic aerosol forcing under the CEDS inventory,while they increased by 0.1-0.8 K under the PKU inventory.The weakening of the EASM index caused by the Asian aerosol forcing under the PKU inventory was twofold greater than that under the CEDS inventory(−0.4 vs.−0.2).The Asian‘dipole-type’aerosol forcing contributed to the observed summer‘southern drought and northern flood’phenomenon in eastern China during 2006-2014.The slow ocean-mediated response to the regional‘dipole-type’aerosol forcing dominated the weakening of the EASM circulation and the precipitation changes in eastern China in the total response.This study further confirms that the biases in anthropogenic aerosol emissions over Asia can affect the CMIP6-based regional climate attribution.