3D modelling of the early martian climate under a denser CO2 atmosphere: Temperatures and CO2 ice clouds

The warming effect of CO2 clouds on early Mars is likely to have been small in reality.

“Hence the warming effect of CO 2 clouds is likely to have been small in reality.”

Recent three-dimensional global climate modeling has shown that cloud coverage close to 100% is never reached in practice.

“Recent threedimensional global climate modeling (Forget et al. 2013; Wordsworth et al. 2013) has shown that this level is never reached in practice.”

The conclusion that a clear-sky CO2-H2O atmosphere alone could not have warmed early Mars has recently been confirmed by three-dimensional climate models that include cloud effects.

“This conclusion, which was reached by Kasting using a one-dimensional clear-sky radiativeconvective climate model, has recently been confirmed by three-dimensional climate models that include cloud effects (Forget et al. 2013; Wordsworth et al. 2013).”

Forget et al. (2013) and Soto et al. (2015) found that collapse of CO2 atmospheres due to surface condensation was extremely significant at low obliquities (below 20°) and at pressures above 3 bar.

“They found that the process was extremely significant at low obliquities (below 20 ◦ ) and at pressures above 3 bar.”

The predictions of Forget et al. (2013) and Soto et al. (2015) differed in detail, partly because Soto et al. (2015) neglected the effects of CO2 clouds and used the present-day solar luminosity.

“The predictions of Forget et al. (2013) and Soto et al. (2015) differed in detail, however, partly because Soto et al. (2015) neglected the effects of CO 2 clouds and used the present-day solar luminosity.”