Agricultural greenhouse gas (GHG) emissions contribute approximately 12% to total global anthropogenic GHG emissions.  Cereals (rice, wheat and maize) are the largest source of human calories, and it is estimated that world cereal production must increase 1.3% annually to 2025 in order to meet growing demand. Sustainable intensification of cereal production systems requires maintaining high yields while reducing environmental costs. We conducted a meta-analysis (62 study sites and 328 observations) to test the hypothesis that the Global Warming Potential (GWP = CH₄+N₂O) of rice, wheat, and maize, when expressed per ton of grain (yield-scaled GWP), is similar, and that lowest values for each cereal is achieved at near optimal yields. Results show that the GWP of rice (3757 kg CO₂ eq ha^-1 season^-1) was higher than wheat (662 kg CO₂ eq ha^-1 season^-1) and maize (1399 kg CO₂ eq ha^-1 season^-1). The yield-scaled GWP of rice was about four times higher (657 kg CO₂ eq Mg^-1) than wheat (166 kg CO₂ eq Mg^-1) and maize (185 kg CO₂ eq Mg^-1). Across cereals, the lowest yield-scaled GWP values were achieved at 92% of maximal yield and was about twice as high for rice (279 kg CO₂ eq Mg^-1) than wheat (102 kg CO₂ eq Mg^-1) or maize (140 kg CO₂ eq Mg^-1), suggesting greater mitigation opportunities for rice systems. In rice, wheat and maize, 0.68%, 1.21% and 1.06% of N applied was emitted as N₂O, respectively. In rice systems, there was no correlation between CH₄ emissions and N rate. Finally, when evaluating issues related to food security and environmental sustainability other factors including cultural significance, the provisioning of ecosystem services, food security, and human health and well-being must also be considered.