FOUR/4 Albedo

STEP ONE: Generate the basic albedo factor of the world by consulting 4.4.1.

Table 4.4.1 Albedo Factor

1d10    Inner Zone    Outer Zone
≤1    (1d10 x 0.01) + 0.75    (1d10 x 0.01) + 0.75
2-3    (1d10 x 0.01) + 0.85    (1d10 x 0.01) + 0.75
4-5    (1d10 x 0.01) + 0.95    (1d10 x 0.01) + 0.85
6    (1d10 x 0.01) + 0.95    (1d10 x 0.01) + 0.95
7    (1d10 x 0.01) + 1.05    (1d10 x 0.01) + 0.95
8-9    (1d10 x 0.01) + 1.05    (1d10 x 0.01) + 1.05
≥10    (1d10 x 0.01) + 1.15    (1d10 x 0.01) + 1.15

Modifications to Inner Zone initial roll
+2 if no atmosphere
+2 if trace atmosphere
-2 if heavy atmosphere (5-49 atms)
-4 if extremely heavy atmosphere (50+ atm)
-2 if ice sheet world (50%-89% of world surface is ice sheet)
-4 if frozen over world (90%+ of world surface is ice sheet)

Modifications to Outer Zone initial roll
+1 if dense atmosphere (1+ atm)
If density separated moon roll on inner zone column


There are several different ways to measure a planet's albedo or reflectivity, and the albedo factor used here is purely a rough estimate to generate surface temperatures. Here, an albedo factor of 1 is Earth-like. A lower albedo factor actually represents a higher albedo, as it will in FOUR/5 generate a lower temperature. In effect, more of the solar infall is reflected. A high albedo factor represents a lower albedo, or a more effective energy absorption.


Albedo factors can provide additional information about a world. Take a world very similar to Earth, but with a higher albedo factor. This world could have much more plant life, more rocky surfaces or perhaps much less clouds. A lower albedo factor could indicate large polar ice caps or much clouds, or perhaps large deserts of sand.

Low Albedo Factors: Common for worlds that either are covered in ice (very common in the outer system) or have an extensive cloud cover. Sand may also explain such albedo.

Moderately Low Albedo Factors: This could be a world with a fairly extensive cloud cover, large ice caps, large deserts or a dirty ice satellite.

Moderate Albedo Factors: These worlds may have varied surfaces, including clouds, oceans or fairly reflective rocks.

Moderately High Albedo Factors: These worlds could be cloudless worlds, all-ocean or jungle worlds but more commonly rocky worlds with some clouds or volcanic rocky worlds.

High Albedo Factors: This may be an atmosphere rich in photochemical compounds (typical in outer system worlds), a world with a dark organic-compound surface (C-class asteroid relatives - these would have very high albedo factors), or a typical rocky world (common on in inner system airless worlds).


Albedo factors can change. Over a year, perhaps, on a world with temporary cloud or ice cover. Over long time if a world freezes over by expanding ice or loses atmosphere. Impacts could trigger cloud covers which could trigger ice ages.


Worlds with little greenhouse effect, and varying albedo factors on the surface, can thus vary in temperature significantly depending on the albedo at a particular spot. This can generate weather effects and is more discussed in Part II.