Global average surface temperatures estimated

FIGURE 23.8 Trends in natural and human influences relevant to Earth s climate during the past four centuries (Lean and Rind 1996). Compared are annual averages of (a) estimates of the solar total radiation, from Figure 23.7c (b) variations in the amount of volcanic aerosols derived from an index (global dust veil index) of known eruptions and (c) the concentration of C02 in the atmosphere. The decade-averaged estimate of the Earth s surface temperature, shown in (d), combines continuous instrumental records from the most recent 150 years with a less certain reconstruction based on various climatic indicators. 

Figure 2.2 shows the average worldwide surface temperature difference of land and sea as compared to the average 20th cenmry temperature of 13.9°C (Global Analysis 2013). The temperature data on the graph were estimated from the information provided by the NOAA (Global Analysis 2013). 

The mean emitted power of the Earth-atmosphere system, 240 W corresponds to a blackbody temperature of 255 K. The surface emission, 390 W m, corresponds to a blackbody temperature of 288 K. The 33 K difference between the blackbody temperatures of the Earth s surface and the Earth-atmosphere system is the so-called greenhouse effect. Increases in concentrations of CO2 and other GHGs since the Industrial Revolution are estimated to have contributed about +2.5 W m to the global and annual average radiation balance (IPCC, 1995). 

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