This study clarifies the need for comprehensive CO2 and non-CO2 mitigation approaches to address both near-term and long-term warming. Non-CO2 greenhouse gases (GHGs) are responsible for nearly half of all climate forcing from GHG. However, the importance of non-CO2 pollutants, in particular short-lived climate pollutants, in climate mitigation has been underrepresented. When historical emissions are partitioned into fossil fuel (FF)- and non-FF-related sources, we find that nearly half of the positive forcing from FF and land-use change sources of CO2 emissions has been masked by coemission of cooling aerosols. Pairing decarbonization with mitigation measures targeting non-CO2 pollutants is essential for limiting not only the near-term (next 25 y) warming but also the 2100 warming below 2 °C.