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The US dairy industry has made substantial gains in reducing the greenhouse gas emission intensity of a gallon of milk. At the same time, consumer and investor interest for improved environmental benefits or reduced environmental impact of food production continues to grow. Following a trend of increasing greenhouse gas emission commitments for businesses across sectors of the economy, the US dairy industry has committed to a goal of net zero greenhouse gas emissions by 2050. The Paris Climate Accord's goal is to reduce warming of the atmosphere to less than 1.5 to 2°C based on preindustrial levels, which is different from emission goals of historic climate agreements that focus on emission reduction targets. Most of the emissions that account for the greenhouse gas footprint of a gallon of milk are from the short-lived climate pollutant CH 4 , which has a half-life of approximately 10 yr. The relatively new accounting system Global Warming Potential Star and the unit CO 2 warming equivalents gives the industry the appropriate metrics to quantify their current and projected warming impact on future emissions. Incorporating this metric into potential future emissions pathways can allow the industry to understand the magnitude of emissions reductions needed to no longer contribute additional warming. Deterministic modeling was performed across the dairy industry's emission areas of enteric fermentation, manure management, feed production, and other upstream emissions necessary for dairy production. By reducing farm-level absolute emissions by 23% based on current levels, there is the opportunity for the US dairy industry to realize climate neutrality within the next few decades., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Environmental concerns involving the dairy industry are shifting from an exclusive focus on water quality to encompass climate change and air quality issues. The dairy industry's climate change air emissions of concern are the greenhouse gases methane and nitrous oxide. With regard to air quality, the dairy industry's major emission contributions are particulate matter, volatile organic compounds, and ammonia. The emissions of these compounds from dairies can be variable because of a number of factors including weather conditions, animal type, management, and nutrition. To evaluate and compare emissions across the diverse operations that comprise the US dairy industry, emissions should be reported per unit of output (e.g., per kg of 3.5% fat-corrected milk). Accurately modeling emissions with models that can predict the complex bio-geochemical processes responsible for emissions is critical to assess current emissions inventories and develop mitigation strategies. Improving the dairy industry's production efficiency (e.g., improvements in management, nutrition, reproduction, and cow comfort) is an effective way to reduce emissions per unit of milk. With accurate process-based models, emissions reductions due to improved production efficiency could be reported per unit of milk and predicted on a farm-to-farm basis., (Copyright (c) 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)