  Coupled models of mantle thermal evolution, volcanism, outgassing,
weathering, and climate evolution for Earth-like (in terms of size and
composition) stagnant lid planets are used to assess their prospects for
habitability. The results indicate that planetary CO$_2$ budgets ranging from
$\approx 3$ orders of magnitude lower than Earth's to $\approx 1$ order of
magnitude larger, and radiogenic heating budgets as large or larger than
Earth's, allow for habitable climates lasting 1-5 Gyrs. The ability of stagnant
lid planets to recover from potential snowball states is also explored;
recovery is found to depend on whether atmosphere-ocean chemical exchange is
possible. For a "hard" snowball with no exchange, recovery is unlikely, as most
CO$_2$ outgassing takes place via metamorphic decarbonation of the crust, which
occurs below the ice layer. However, for a "soft" snowball where there is
exchange between atmosphere and ocean, planets can readily recover. For both
hard and soft snowball states, there is a minimum CO$_2$ budget needed for
recovery; below this limit any snowball state would be permanent. Thus there is
the possibility for hysteresis in stagnant lid planet climate evolution, where
planets with low CO$_2$ budgets that start off in a snowball climate will be
permanently stuck in this state, while otherwise identical planets that start
with a temperate climate will be capable of maintaining this climate for 1 Gyrs
or more. Finally, the model results have important implications for future
exoplanet missions, as they can guide observations to planets most likely to
possess habitable climates.
