Readers of Ben Sandilands’ yesterday may be confused by the suggestion that a climate change “debate” is taking place based on cyclic variations in solar radiation. But this ignores the fact that solar variations are one order of magnitute lower than the effects of rising greenhouse gas levels, in terms of temperature effects on the Earth. So whereas the 11 (+/-1 to 2) years-long sun spot cycle results in temperature variations of +/-0.1 to 0.2 degrees C, the greenhouse gas levels have affected a rise of +0.7 degrees C since mid-20th century.

For those of you who may be uncertain about the role of the sun in global warming, allow me to explain.

In the face of overwhelming evidence of severe climate disruption by the world’s leading research organisation (NASA, Hadley-Met, CSIRO, Potsdam, numerous universities), a denial syndrome continues to resort to long-discarded arguments, including variations in solar insolation.

However, according to Sami Solanki, an international authority in solar science, “solar variability is unlikely to have been the dominant cause of the strong warming during the past three decades”.

The luminescence effect of solar magnetic storms (sun spots) on the Earth surface is an order of magnitude less than the effects of rising CO2 gases since the midth 20th century. Sun spot variations account for changes of less than +/-0.4 Watt/m2 (+/-0.1 to 0.3 degrees C). For example, the change from near-zero sun spots during 1650 — 1700AD (“Maunder Minimum) to near-150 sun spots at 1800AD correlates with temperature rise of +0.3 degrees C. The change from about 70 sun spots at 1900AD to near-180 sun spots at 1950AD correlates with +0.25 C.

According to the IPCC AR4 Report (Fig. TS5) the solar factor accounts for 0.06 – 0.30 Watt/m2 (less than 0.2C) rise since 1750AD. NASA’s Goddard Institute of Space Science indicates total solar irradiance variations of +/-0.3 Watt/m2 (~0.2C) since 1980. Solar vriations can not account for the sharp temperature rise since 1960, a period during which sun spot activity oscillated (correlated with +/-0.1 degrees C), hardly consistent with the +0.7 degrees C rise induced by CO2 rise from 315 to 387 ppm.

Another parameter of global warming is the intensification in the frequency and intensity of the ENSO cycle (El-Nino Southern Oscillation) (Power and Smith, Geophys. Res. Lett., 2007), expressed by cyclic surface warming up to 2 degrees C in the central Pacific, with a peak in 1998, affecting droughts in the southern continents.

But climate “skeptics” can expect some “good news”. Should further melt of Greenland ice and slow down of the Gulf Stream take place, resulting in freezing temperatures in Europe and northeast USA, no doubt the “skeptics” will resume their claims of “global cooling”.

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Peter Fray
Peter Fray
Editor-in-chief of Crikey
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