Greenhouse gas analysis at global scale using the CAMS EGG4 product

• Chengdu led global CO 2 emissions followed by Luoyang, Chongqing, and Los Angeles. • Katowice had highest CH 4 emissions, trailed by São Paulo, Lahore, and Delhi. • CO 2 levels rose from 394.470–394.477 ppm in 2003 to 394.501–394.510 ppm in 2020. • CH 4 levels increased from 1831.3–1833.3 ppb to 1832–1834.5 ppb over 17 years. • Minimum land surface air temperature rose by 2 °C, from −54.49 °C to −52.20 °C. This study examined global atmospheric variations in carbon dioxide (CO 2 ) and methane (CH 4 ), which are two major greenhouse gases (GHGs). The main objectives were as follows: (1) identify the top 50 cities with the highest CO 2 and CH 4 emissions, (2) analyze 17-year trends in emissions in cities worldwide, (3) conduct a spatiotemporal analysis of CO 2 and CH 4 emissions from 2003 to 2020, (4) quantify changes in GHG emissions during this period, and (5) assess the impact of GHG emissions on land surface air temperature (LSAT). These objectives were achieved using the global ERA5 reanalysis data from the Copernicus Climate Change Service. The findings indicated that Chengdu (China) had the highest cumulative CO 2 emissions between 2003 and 2020, followed by Luoyang (China), Chongqing (China), Myitkyina (Myanmar), Louangphrabang (Laos), Lampang (Thailand), Louang Namtha (Laos), Aizawl (India), Nola (Central African Republic), and Los Angeles (USA). Katowice (Poland) exhibited the highest CH 4 emissions, followed by São Paulo (Brazil), Lahore (Pakistan), Delhi (India), New Delhi (India), Moscow (Russia), Chengdu (China), Anshan (China), Andijan (Uzbekistan), and Fergana (Uzbekistan). Between 2003 and 2020, the mean annual atmospheric CO 2 concentration increased from 394.470–394.477 ppm to 394.501–394.510 ppm, whereas the CH 4 concentration increased from 1831.3–1833.3 ppb to 1832–1834.5 ppb. The analysis revealed significant increasing trends in CO 2 and CH 4 emissions globally, with certain cities exhibiting sharper increases. The LSAT also increased during the study period, with the minimum LSAT increasing by 2 °C (from − 54.49 °C to − 52.20 °C). This comprehensive analysis highlights the urgent need to address GHG emissions to mitigate their environmental and climatic effects.