The Sun Controls the Earth's Climate

The source of more or less energy for the Earth is the Sun. The output of UV radiation is particularly variable for the Sun with variations of 0.5 to 0.8%. This UV radiation affects the ozone concentrations in the atmosphere, the energy deposited in the upper atmosphere, and the winds in the upper atmosphere. It affects the amount of sulfur moved from the oceans into the atmosphere, which then affects lower atmosphere cloud cover, which then reflects light back into space. Overall, the energy from the Sun measured by satellites since 1979 has varied by 0.22%. The high to the low energy output were separated by only 7 years. This difference causes a surface temperature difference of at least 0.45 degree C, according to Ian Plimer. He also says the urban warming effect was 0.1 degree C for a total warming of 0.55 degree C. This is about equal to the late 20th Century temperature increase. This was an irradiance variation of about 0.53 Watts/meter squared.

Since most of this period has been one of relatively high solar activity and output, there is reason to believe that longer term measurements will show much larger variations in solar output. If the Sun's irradiance were to be only about 1 to 1.5 Watts/meter squared less than now, we would experience conditions equivalent to the very cold Maunder Minimum of the Little Ice Age. The 23rd Sun cycle was very short, being 10.0 years long rather than the average of 11.1 years, and resulted in a large decrease in solar irradiance. The quiet sunspot Cycle 24 has started and by September 2008 there were 200 consecutive days without sunspots. The very cold Dalton Minimum of the early 1800s was the last time something like this happened. Some astronomers believe that temperatures will start falling due to solar inactivity between 2012 to 2015 and reach a minimum in solar energy in 2040. This will result in the Earth being very cold around the period of 2055 - 2060.

If the temperature of the Earth is primarily due to the Sun's activities, then the other planets should be similarly affected. They are. In 1998, the Hubble telescope discovered that Triton, the moon of Neptune, had warmed since 1989 when a space probe visited it. Measurements on Pluto showed its temperature to have risen 2 degrees C. The Hubble telescope also measured a 1 degree C increase in the temperature of Jupiter in 2006. Mars has been found to have had a temperature increase of 0.65 degrees C between the 1970s and the 1990s, which is very close the 0.7 degree C increase in temperature on Earth in the last century.

Ian Plimer makes a very good case that the Earth's temperature responds primarily to changes in the activity of our Sun. The IPCC computer models greatly underestimate the effects of the Sun and greatly overestimate the effects of CO2 concentrations in the atmosphere. I again strongly recommend Ian Plimer's book Heaven and Earth.