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Climate forcings by individual greenhouse gases: (A) CO2, (B) CH4 and N2O, (C) CFC-11 and CFC-12, based on trace gas data available from the National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory (K. Masarie, personal communication). For 1958–1985, when annual CH4 data are not available, we used a constant 15 ppb annual change estimated from ice core and other data (23).
