Direct Measurements of Surface Forcing of Carbon Dioxide from 2000 to 2010

Earth's background atmospheric CO2 concentration has recently passed 400 ppmv, and its increase by 125 ppmv since 1750 has implications for the radiative balance of the Earth's atmosphere. The physics governing how atmospheric CO2 concentrations influence atmospheric infrared energy balance, and thus climate, are well established, but the impact of recent atmospheric CO2 trends on the surface energy balance has not been experimentally confirmed in the field. Using infrared CO2 absorption bands and controlling for atmospheric temperature and water vapor, spectra from the DOE ARM Program's Atmospheric Emitted Radiance Interferometers (AERI) yield the first direct observational evidence of the time-series of CO2 surface radiative forcing directly attributable to the 23 ppmv atmospheric CO2 increase between 2000-2010. The time-series shows a secular trend of 0.2 W/m2/decade with seasonal and diurnal ranges of 0.5 W/m2. This data record provides the first comprehensive observational evidence of surface radiative forcing by CO2, confirming theoretical predictions of the atmospheric greenhouse effect.