The faint young sun‐climate paradox: Continental influences

We examine the various mechanisms which have been proposed to compensate for the climatic effects of a 30% increase in the solar luminosity over the past 4½ billion years. Although atmospheric greenhouse effects have received most attention, other mechanisms may have played a role of comparable importance. In particular, we note that the development of continents during the past 2½ billion years could have had a significant secular effect on the atmosphere‐ocean heat transport system. As a result, past climates may have been less susceptible to complete freeze‐over. A simple energy balance model is used to demonstrate the magnitude of this effect. Because the CO 2 greenhouse effect is not the only means of compensating for solar evolution, the faint‐young‐sun problem should not be used to infer past levels of atmospheric CO 2 .