SUB-NEPTUNES

Despite receiving just 30% of the Earth's present-day insolation, Mars had water lakes early in the planet's history, due to an unknown warming mechanism. A possible explanation for the >10 2 yr-long lake-forming climates (Haberle et al. 2017, Kite 2019) is warming by water ice clouds (Segura et al. 2008, Urata & Toon 2013). However, this cloud greenhouse has proved difficult to replicate, and has been argued to require unrealistically high-altitude optically thick clouds (Wordsworth 2016, Ramirez & Kasting 2017). Here, we use a global climate model (GCM) to show that a cloud greenhouse can warm a Mars-like planet to global average annual-mean temperature (T) 265 K, which is warm enough for low-latitude lakes, and stay warm for centuries or longer, but only if the planet has spatially patchy surface water sources. Warm, stable climates involve surface ice (and low clouds) only at locations much colder than the average surface temperature. At locations horizontally distant from these..

Primary location: Chicago United States