India and China are two similar developing countries with huge populations, rapid economic growth and limited natural resources, therefore facing the massive pressure of ensuring food security. In this paper, we will discuss the food security situations in these two countries by studying the historical changes of food supply-demand balance with the concept of agricultural land requirements for food (LRF) from 1963–2009. LRF of a country is a function of population, per capita consumption/diet, cropping yield and cropping intensity. We have attempted to discuss and compare our results in a framework which links consumption of different groups of food items to diet patterns; then, to the total land requirement for food in a scenario when population is growing rapidly and diet diversification and urbanization due to economic reform impose excessive pressure on food security of both countries. We also elaborate on the role of technology dissemination and critically analyze the achievements and drawbacks of government policies to ensure food self-sufficiency and food security of nations. Our results show that the total LRF increases approximately by 42% and 40%, whereas per capita LRF decreases significantly by about 48% and 30% from 1963–2009, for India and China, respectively. Furthermore, our studies reveal that population growth dominates most of the increase in total LRF for India; whereas diet pattern change induced by income growth drives the major increase in LRF for China. Therefore, sustainable management of agricultural land resource is an urgent need both for India and China as there will be demand for more food to meet the diet requirement for the entire population. We also demonstrate the role of India and China in future global food security programs and the challenges to implement the new land reform policies domestically.

Satellite observations show that carbon monoxide (CO) concentration centers exist in the tropopause region of the Tibetan Plateau, while their sources and formation mechanism still remain uncertain. In this paper, the 3-D chemical transport model GEOS-Chem is used to conduct sensitivity analysis in 2016. Combined with the analysis data and satellite data, the contribution of three important emission sources (South Asia, East Asia and Southeast Asia) and two important chemical reaction species (CH₄ and nonmethane volatile organic compounds (NMVOCs)) to CO in the upper troposphere and lower stratosphere (UTLS) are studied. The results show that in the Asian monsoon region CO emissions originating from the surface are transported to the upper troposphere via a deep convection process and then enter the Asian Summer Monsoon (ASM) anticyclone. The strong ASM anticyclone isolates the mixing process of air inside and outside the anticyclone, upon entry of carbon monoxide-rich air. In the lower stratosphere, the intensity of the ASM anticyclone declines and the air within the anticyclone flows southwestward with monsoon circulation. We found that in the summer Asian monsoon region, South Asia exhibited the highest carbon monoxide concentration transported to the UTLS. CH₄ imposed the greatest influence on the CO concentration in the UTLS region. According to the model simulation results, the CO concentrations in the Asian monsoon region at 100 hPa altitudes were higher than those in other regions at the same latitudes. Regarding effects, 43.18% originated from CH₄ chemical reactions, 20.81% originated from NMVOC chemical reactions, and 63.33% originated from surface CO emissions, while sinks yielded a negative contribution of −27.32%. Regarding surface CO emissions, East Asia contributed 13.56%, South Asia contributed 39.27%, and Southeast Asia contributed 7.15%.