Global oil refineries emit a significant amount of CO2, contributing to climate change. A study analyzed data from over 1,000 refineries from 2000 to 2018 and found that they emitted 1.3 gigatonnes of CO2 in 2018. Without changes, they could emit 16.5 gigatonnes during 2020-2030. By improving efficiency and upgrading technologies, emissions could be reduced by 10% during that period.