Gas Flaring Is Likely Underestimated by Satellites due to Undetected Small Flares

Global upstream oil and gas flaring was estimated at 148 billion m³ in 2023 based on satellite observations by the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument. Accurate monitoring is critical, as both lit and unlit flares release greenhouse gases and pose health risks. However, we show that VIIRS substantially underestimates flaring in Canada, with implications for other regions. Analyzing over 65,000 annualized industry flare reports (>5000 sites per year) in western Canada over more than a decade (2012-2023), we found that VIIRS consistently estimated lower flaring volumes than industry data. In 2023, for example, industry reported 2.2-times more flaring than VIIRS estimated, across more than 14-times as many sites. Most of this discrepancy (76%) was due to undetected small and/or intermittent flares with flow rates <360 m³/h (∼220 kg methane/h); the remainder (24%) was the result of enclosed combustor use, whose shielded flames are not readily detected. Comparison with global VIIRS data revealed similar declines in flare detection at low flow rates, suggesting that underestimation may occur in other regions where similar low to medium flare flow rates are common.