In the last decade, there has been no clear warming trend (as the UK Met Office and IPCC’s own figures demonstrate). In the last century, much of the warming occurred prior to 1940, when human emissions of CO2 were relatively small compared to today. During the post-war economic boom (when one would have expected the temperature to rise) the world cooled, from the 1940s till the mid-70s (again, this is evident from accepted data used by the IPCC).”
Frederick Seitz and Robert Jastrow. “Do people cause global warming? What the scientific evidence reveals”. Environment News. December 1, 2001 – “The first thing to note is that the 100 years of global warming occurred in two stages–a temperature rise of approximately a half-degree Fahrenheit early in the century from 1910 to 1940, and another half-degree temperature rise toward the end of the century in the 1980s and 1990s…Between these two periods of warming, from the 1940s to the 1970s, the Earth actually cooled somewhat. Greenhouse gases like carbon dioxide cannot cool the planet; they can only warm it. So we have to conclude that some other natural factors in climate change were at work in those middle decades of the century.
For example, we know the brightness of the sun changes now and then; if the sun’s brightness decreased, that would cause a global cooling.
It has been suggested that the cooling effect of aerosols is the explanation for the occurrence of the global cooling in the 1950s and 1960s, rather than the predicted global warming. Aerosols are small particles which partly screen the earth from incident sunlight and tend to cool the planet.”