Chapter 2: The big bad sun and its solar winds
The earth receives the right amount of solar radiation to heat it to temperatures that allow for life to exist. The levels and intensity of this radiation fluctuate over an eleven-year cycle as well as simultaneously changing over centenniel and longer cycles (Lean, Beer and Bradley, 1995). Fig. 1 shows the eleven-year cycle of solar activity. This is a popular hypothesis for why the earth’s climate fluctuates. Another factor influencing climate change is the concentration of greenhouse gases in the atmosphere.
The radiation emitted from the sun varies in a cyclical pattern that takes place over a period of eleven years. During this cycle the sun gradually warms and then cools and then warms again (Foukal et al. 2004). The temperature on earth correlates to the solar radiation cycle directly. When the there is an increase in solar radiation the temperature on earth increases and when the cycle brings about less solar radiation, the temperature on earth decreases. This has been shown to be evident through global air temperature readings gathered between 1880 and 2001 (Lean, Beer and Bradley, 1995).
Solar forcing is a term used to describe the sun’s effect on climate changes on earth. Other examples of forcing include volcanic and oceanic forcing. As Lean, Beer and Bradley (1995) report in their Reconstruction of Solar Irradiance since 1610 it is likely that solar forcing is responsible for half the observed 0.55 °C increase in temperature over 120 years and at least a third since 1970 (1995).
In a more recent study conducted in 2009, Lee et al reveal that solar forcing is responsible for significant changes in the climate including increases in humidity as well as enhancing the ascending branch of the Hadley cell around the equator. It also found a correlation between increased solar activity and the northward movement of the intertropical convergience zone (ITCZ). This correlation shows that solar cyclic activity impacts on our climate systems. The evidence for links between climate change and the sun have been stifled in the past by poor proxy models. However, Versteegh (2005) argues that with the examination of new evidence along with historical information, there is a strong enough correlation between solar activity and the climate on earth to warrant further study. Rind et al. (2004) argue through the analysis of historical records and modern proxy models there is a direct correlation between solar activity and the climate of the planet.
Thus to conclude this chapter, one of the main reasons for global warming is the increase in solar activity from the sun. An increase in solar winds makes for an increase in earth's atmospheres and effectively makes the planet rise in temperature. Luckily for mankind, the earth is not build from a house of straws or wood but from a strong base; a protective atmosphere that helps to make the impact of the solar winds minimal, thus making the world not being able to get blown down immediately.
