We infer the year-to-year variability of net global air-sea CO₂ fluxes from observed interannual changes in wind speed and estimated differences in CO₂ partial pressure between surface seawater (pCO_2SW) and the overlying atmosphere. Changes in pCO_2SW are estimated from changes in sea surface temperature via seasonal algorithms that relate pCO_2SW to sea surface temperature. Our diagnostic model yields an interannual variability of ±0.18 petagrams (1σ, Pg = 10¹⁵ grams) of carbon per year for the period 1982–2001. El Niño Southern Oscillation–induced changes in the equatorial efflux contribute approximately 70% of the diagnostic modeled global variability. Regional flux anomalies for areas outside the equatorial Pacific are found to neither systematically reinforce nor counteract each other during times of transition from El Niño years to normal years. The interannual variability of ±0.18 Pg C yr⁻¹ obtained in the present work is at the low end of previous estimates that falls in the range of ±0.2 to ±0.5 Pg C yr⁻¹. Of the previous estimates, lower values are generally estimated from global ocean circulation–biogeochemical models, while higher values are derived from atmospheric inversion models constrained by atmospheric CO₂ observations. Comparisons of our modeled results with two time series data sets and equatorial Pacific data suggest that our diagnostic model is not able to capture the full range of pCO_2SW variations; this is probably due to the inability of the empirical model to fully account for changes in surface pCO_2SW related to ocean biological and physical processes. The small interannual variability in our modeled fluxes suggests that observed year-to-year variations in the rate of atmospheric CO₂ increase are primarily caused by changes in the rate of CO₂ uptake by the land biosphere.