Quantifying the annual flux of CO₂ (carbon dioxide) and equivalent emissions to the atmosphere is critical for both policy decisions and modeling of future climate change. Given the importance of greenhouse gas emissions to climate change and a recognized mismatch between sources and sinks (e.g., Liu & Dreybrodt , 2015), it is important to quantify these parameters. A significant and previously unrecognized CO₂ contribution arises from groundwater depletion (net removal from storage). The average annual 1.7 MMT (million metric tons) CO₂ released in the United States from this source is greater than approximately one third of the 23 major sources reported by the US EPA (United States Environmental Protection Agency) to the IPCC (Intergovernmental Panel on Climate Change; US EPA, 2016 ).