English: This graph shows the growth in direct climate forcing (warming influence) from long-lived and well-mixed greenhouse gases in earth's atmosphere during the industrial era. The forcing is represented as a normalized index, defined by the authors as the Annual Greenhouse Gas Index (AGGI), and is displayed as the red curve. For comparison, the graph also shows the growth in the measured atmospheric concentration of these gases. The total concentration of all gases included in the index is represented as an equivalent mixing ratio of CO2 and is displayed as the black curve.

The authors further clarify the graph as follows: "Changes in radiative forcing before 1978 are derived from atmospheric measurements of CO2, started by C.D. Keeling [Keeling et al., 1958], and from measurements of CO2 and other greenhouse gases in air trapped in snow and ice in Antarctica and Greenland [Etheridge et al., 1996; Butler et al,, 1999]. These results define atmospheric composition changes going back to 1750 and radiative forcing changes since pre-industrial times. This longer-term view shows how increases in greenhouse gas concentrations over the past ~70 years (since 1950) have accounted for three-fourths (72%) of the total increase in the AGGI over the past 260 years."

References:

• Butler, J.H. and S.A. Montzka (2013-08-01) THE NOAA ANNUAL GREENHOUSE GAS INDEX (AGGI) ^[1], NOAA/ESRL Global Monitoring Division

Keeling, C.D., (1958), The concentration and isotopic abundances of atmospheric carbon dioxide in rural areas, Geochimica et Cosmochimica Acta, 13, 322–334.

Etheridge, D.M., L.P. Steele, R.L. Langenfelds, and R.J. Francey, (1996), Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn, J. Geophys. Res. 101, 4115–4128.