A Greenhouse Gas Budget for Mexico During 2000–2019.

Application of the best available science to improve quantification of greenhouse gas (GHG) emissions at regional and national scales is key to climate action. Here, we present a two‐decade (2000–2019) GHG (CO2, CH4, and N2O) budget for Mexico derived from multiple products. Data from the National GHG Inventory, global observations, and the scientific literature were compared to identify knowledge gaps on GHG flux dynamics and discrepancies among estimates. Total mean annual GHG emissions were estimated at 695–910 TgCO2‐eq year−1 over these two decades, with 70% of the emissions attributable to CO2, 23% to CH4, and 5% to N2O (2% to other gases). When divided by sectors, we found agreement across emission estimates from various sources for fossil fuels, cattle, agriculture, and waste for all GHGs. However, considerable discrepancies were identified in the fluxes from terrestrial ecosystems. The disagreement was particularly large for the land CO2 sink, where net biome production estimations from the national inventory were double those from any other observational product. Extensive knowledge gaps exist, mainly related to aquatic systems (e.g., outgassing in rivers) and the lateral fluxes (e.g., wood trade). In addition, limited information is available on CH4 emissions from wetlands and soil CH4 consumption. We expect these results to guide future research to reduce estimation uncertainties and fill the information gaps across Mexico. Plain Language Summary: Mexico represents the 13th global emitter of greenhouse gases (GHGs) and the second among Latin American countries, releasing roughly 485 million tons of CO2, six million tons of CH4 (equivalent to 160 million tons of CO2), and 0.1 million tons of N2O (equivalent to 35 million tons of CO2). However, large uncertainties prevail in the estimation of several components of each flux; thus, the application of the best available science to account for and improve these estimations is essential for sound mitigation policies. Here, we used multiple available products (national inventories, satellites, flux towers, dynamic global vegetation models, inversion models, and other data sources) to advance our understanding of the GHG budget of Mexico over the last 20 years. We found that fluxes from fossil fuel combustion (including energy production, transportation, industry, etc.), agriculture, livestock, and waste management agree remarkably well across products. In contrast, we documented large differences among products for land‐based fluxes (e.g., CO2 capture) and scant available information on aquatic ecosystems (e.g., CH4 emission from wetlands) and on lateral fluxes (e.g., emissions from trade). We expect these results to help in guiding future measuring efforts and policies to mitigate GHG emissions from Mexico. Key Points: A greenhouse gas (GHG) budget for Mexico was calculated based on multiple products. We estimated fluxes for CO2, CH4, and N2O over the 2000–2019 periodTotal GHG emissions were 695 TgCO2‐eq year−1 in the national inventory and as much as a mean 910 TgCO2‐eq year−1 across productsGHG fluxes agreed well across products for emissions, but large discrepancies exist for the land CO2 and CH4 sinks [ABSTRACT FROM AUTHOR]