A general circulation model study of the effects of faster rotation rate, enhanced CO₂ concentration, and reduced solar forcing: implications for the faint young Sun paradox

The control simulation of this study has a solar constant reduced by 10% the present amount, zero land fraction using a swamp ocean surface, CO₂ concentrations of 330 ppmv, present-day rotation rate, and is integrated under mean diurnal and seasonal solar forcing. Four sensitivity tests are performed under zero land fraction and reduced solar constant conditions: 1) increased rotation rate, 2) 8 times present CO₂, 3) a combination of 1 and 2, and 4) 3 with a 15% reduction in the solar constant. Results indicate the following changes in the global mean sea surface temperatures (SSTs) compared to the control simulation: 1) +6.6 K, 2) +12 K, 3) +18.5 K, and 4) +6.6 K relative to the control's global mean temperature of 264.7 K. Sea ice is confined to higher latitudes in each experiment compared to the control, with ice-free areas equatorward of the subtropics. The warm SSTs are associated with a 20% reduction in clouds for the rotation rate experiments and higher CO₂ concentrations in the other experiments. -from Author