|first-order climate forcing|
A forcing that affects the global mean temperature. As opposed to forcings that might be important locally but don't have much impact on overall global warming.
1. For more information, click here to read Gavin Schmidt's more detailed explanation.
2. Usage example: "To my mind, the ‘first-order' forcings would be the ones without which you can't really do without in assessing global climate change. I would therefore argue that for the global mean the well-mixed GHGs and the counterbalancing reflecitve aerosol effects are ‘first-order' – without GHGs there is no appreciable warming signal, and without the aerosols, the warming from GHGs is excessive and important changes in the diurnal cycle and cloudiness are not captured." (Real Climate)