I think the single most important condition for the Gaia effect is not only liquid water. Water in dynamic contact with rock and atmosphere is the key imo. On Earth the control of global temperature to provide the best environment for much life is tightly linked to atmospheric carbon dioxide concentration. Geochemistry and hydrology conspire to add atmospheric carbon when things get cold, then fix that carbon when things get too hot. During the (sic!) Carboniferous, a period of high heat, humidity and oxygen content, much carbon was sequestered in what would become coal seams.
Later during the Triassic, another very hot era, much carbon was bound inorganically as limestone. The Gaia effect, at least as illustrated by biogenic global temperature regulation, is a very nice illustration of what chemists call negative cooperativity. It is not an unstable steady state, but one with strong stabilizing features.
... Some have theorized that, with pre-industrial carbon dioxide levels already quite low, and with the relentless increase in solar brightness that results from that star's continuing internal changes, the Earth will run out of "climate margin" in a few hundred million years, or even sooner. The pseudoequilibrium would give way to a runaway planetary greenhouse, boiling the oceans.
...Unless by then posthuman technical activities have shaded or moved the planet - or installed a solar thermostat.
cheers js |
