# What is the albedo of a habitable planet?

What is the albedo range for an Earth-like planet? I need to know because it's important for determining the inner and outer edges of the habitable zone. I'm thinking in terms of cloud/water-ratio (I'm assuming that water has a low average albedo of 0.10 and clouds have a high average albedo of 0.70, correct me if these estimates are way off).

• check out Enceladus, Saturn's moon suspected to contain the building blocks for life but it is also one of the highest bond albedo of 0.81 or 81% of all sunlight are reflected back into space for comparison Earth is 0.29 ðŸª© Commented Jan 11 at 4:34

Simple answer: Somewhere around 0.3 is good.

Longer answer: It really depends on greenhouse effect.

The following is an equation for surface temperature from https://web.archive.org/web/20210605120431/https://scied.ucar.edu/earth-system/planetary-energy-balance-temperature-calculate

Working out the equation with earth's values, we get a global temp of -19 Celsius. This is obviously not earth's temperature, and the equation is wrong because it doesn't account for greenhouse effect at all. Plugging the equation into a graphing software like Desmos, it can be seen that even at 0 albedo, the temp is only 5 degrees (although at ~99% albedo it reaches -200 degrees.) As such, with enough fidgeting with greenhouse gas levels, you can basically make the albedo anything you like, and I doubt any combination of water and cloud/ice would produce an albedo extreme enough that it couldn't be accounted for.

To cool the planet (for albedos <0.3), you could replace some of the ~80% nitrogen (a greenhouse gas) in the atmosphere with something like argon, which allows humans to breathe in the same way nitrogen does (although some nitrogen is necessary for DNA to form), and to warm the planet (for albedos >0.3), you could either increase carbon dioxide or water vapour (water vapour being a potent greenhouse gas).