Int. J. Environ. Res. Public Health 2011, 8 998 the climate sensitivity factor (CSF) for the effect of doubling CO2 on global temperatures alone is widely believed to be small (as discussed below and in Section 2.3.1.4). More than 90 percent of the greenhouse effect is due to water vapor and is significantly affected by the extent of cloud cover; CO2 from fossil fuel burning does increase the atmospheric CO2 level slightly, but represents less than 0.1 percent of the greenhouse effect (as illustrated in Figure 3) according in Segalstad [8]. Figure 3. Major role of water vapor and very minor role of CO2 in the greenhouse effect. Source: [8], Slide 18. Archibald [20] points out that ―the effect of carbon dioxide on temperature is logarithmic and thus climate sensitivity decreases with increasing concentration,‖ so that further increases in atmospheric CO2 would have very little effect on global temperatures. Further, he finds that: ―The first 20 ppm of carbon dioxide has a greater temperature effect than the next 400 ppm. The rate of annual increase in atmospheric carbon dioxide over the last 30 years has averaged 1.7 ppm. From the current level of 380 ppm, it is projected to rise to 420 ppm by 2030. ―The projected 40 ppm increase reduces emission from the stratosphere to space…This… equates to an increase in atmospheric temperature of 0.04 °C. ―Increasing the carbon dioxide content by a further 200 ppm to 620 ppm, projected by 2150, results in a further 0.16 °C increase in atmospheric temperature. ―Since the beginning of the Industrial Revolution, increased atmospheric carbon dioxide has increased the temperature of the atmosphere by 0.1 °C.‖