Quantifying greenhouse gas (GHG) emissions is a critical task for climate monitoring and mitigation actions.  Under the Paris Agreement, for example, accounting and reporting of GHG emissions are mandatory for Parties.  Reported emissions are often calculated using activity data approaches.  The robustness of the activity data collection is a key for obtaining accurate emission estimates; however, in a period of open conflict or war, the systems for data collection can be desperately damaged and destroyed and thus the ability of achieving robust GHG estimates and transparent reporting can be significantly hampered.  Also, military emissions, which are thought to be often poorly quantified, should increase significantly than peace times. 

We attempted to quantify GHG emissions during the first 18 months of the 2022/2023 full-scale war in Ukraine.  We first identified major, war-related, emission drivers and processes from the territory of Ukraine.  We analyzed publicly available data and used expert judgment to estimate emissions from (1) the use of bombs, missiles, barrel artillery, and mines; (2) the consumption of oil products for military operations; (3) fires at petroleum storage depots and refineries; (4) fires in buildings and infrastructure facilities; (5) fires on forest and agricultural lands; and (6) the decomposition of war-related garbage/waste.  Those sources are often not covered by current GHG inventory guidelines, and thus are not likely to be included in national inventory reports. 

Our estimate of the war-related emissions of carbon dioxide (CO2), methane, (CH4) and nitrous oxide (N2O) for the first 18 months of the war in Ukraine is 77 MtCO2-eq. with a relative uncertainty of ±22 % (95 % confidence interval).  It is important to note that these emissions are considered to be emissions from Ukraine in reporting because the emissions occurred within the territory of Ukraine.  The current emission accounting system (e.g. UNFCCC) is not designed to account war/conflict time emissions adequately.  The uncertainties due to the unaccounted emissions are also aliasing to our global and regional carbon budget calculations.