Solar luminosity change

The Earth s climatic system can be thought of as a well-adjusted thermostat. It is quite clear that it will not be insensitive to changes in the luminosity of our star. Solar luminosity is expected to rise linearly by about 10% over the next billion years, whilst the surface temperature will increase by 1 %. Naturally, supernova specialists would be quite unmoved by such a variation. In their field, luminosities rocket to quite unheard-of values in the merest fraction of a second. But to climate specialists back within the confines of the Earth s atmosphere, an increase of 10% in the Sun s brightness is an alarming prospect. 

If the solar luminosity increases by 2%, the climate model produced by the Goddard Institute for Space Studies indicates a corresponding temperature increase of 4 °C. Climatologists do not usually make predictions over billions of years so this model has not been pursued. However, we may consider that a 10% increase in solar luminosity would lead to a temperature rise of around 12 °C. The result would certainly be catastrophic. Sea level would rise by some 40 cm as the ice caps melted. With a temperature increase of 21 °C, the ice caps would vanish completely and the climate would be changed forever. 

Figure 11 Comparison between the fluctuations in the fraction of red-coated lithic grains (dashed curve) with that of cosmogenic nuclide production (smooth curve) in the Earth s atmosphere. This correspondence provides powerful evidence that the Holocene s small cyclic temperature changes were paced by changes in solar luminosity (source...

Fig. 1. Global average surface temperatures and atmospheric CO2 levels predicted by models in which CO2 is the only greenhouse gas and the temperature dependence of subaerial silicate weathering is the only effective buffer against changing solar luminosity. One PAL indicates one present atmospheric level of 300 ppm. Curves are labelled by the weathering parameter p (equation (8)). These models are inspired by Walker et al. (1981). Constant CO2 is shown for comparison. Unless silicate weathering is nearly independent of pCQ>2 (P < 0-2), ancient climates are cool.

Ringwood, a. E. 1961. Changes in solar luminosity and some possible terrestrial consequences. Geo-chimica et Cosmochimica Acta, 21, 295-296. 

Mariner 9 images showed equatorial sinuous channels on Mars. Sagan, Toon and Gierasch, 1973 [288] mentioned two possible stable climates one that resembles the present day climate on Mars, the other which has atmospheric pressure of about 1 bar. The triggers for a transition from one state to another are changes in the obliquity, solar luminosity and albedo variations of the polar caps. 

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