Environment (ENV) ratings are based primarily on climate, but also reflect the extremes possible at TAQ 9. Sea levels in meters above/below baseline Earth.
ENV Environment Sea Lvl Hydro Era
0 Freezing -200 62% Snowball Earth
1 Freezing -150 64% Snowball Earth
2 Cold -125 65% Icehouse Earth-Glacial
3 Cold -100 66% Icehouse Earth-Glacial
4 Cold -75 67% Icehouse Earth-Glacial
5 Cold -50 68% Icehouse Earth-Glacial
6 Normal -25 69% Icehouse Earth-Interglacial
7 Normal +/-0 70% Icehouse Earth-Interglacial
8 Normal +20 71% Icehouse Earth-Interglacial
9 Normal +40 72% Icehouse Earth-Interglacial
A Warm +60 73% Greenhouse Earth
B Warm +100 75% Greenhouse Earth
C Warm +160 78% Greenhouse Earth
D Warm +200 80% Greenhouse Earth
E Hot +300 85% Greenhouse Earth
F Hot +400 88% Greenhouse Earth
G Reducing -- -- Rockball (pre-biotic)
H Reducing -- -- Iceball
J Reducing -- -- Exotic biology
K Corrosive -- -- Runaway Greenhouse
TAQ 3 worlds (and Earth) are all ENV 7. Sea levels are in meters from baseline. Hydrographic (Hydro) is the portion of the world’s surface covered by ocean. Era describes the prevalent geoclimatic type for comparison to baseline paleoclimate models. Reducing environments have no free oxygen to breathe. Corrosive environments require special protective measures.
I have a method for generating environment scores based on TAQ that produces satisfactory statistics, but it’s a bit of a mess and I need to refine it more before it’s ready to share.
I’m not sure what you mean by “greenhouse.” I’m used to its being used for Venus-style world; that’s how GURPS Space defines it. If it means simply that there’s a greenhouse effect, well, our Earth has a nontrivial greenhouse effect.
And I’m not sure what the units are for sea level, though I assume this is like the maps in H.G. Wells’s The Science of Life that show earth with lower and higher sea level, and that this is an effect of mean planetary temperature, not a cause.
“Greenhouse Earth” is a term of art in paleoclimate studies. It essentially covers the periods when there are no glaciers or ice caps anywhere on Earth, as opposed to “Icehouse Earth” where there are. Icehouse periods alternate between “glacial” and “interglacial” episodes, depending on how far the ice extends. Present-day Earth has been in an interglacial period since about 18kya (the Younger Dryas was a blip on the long term trend).
My challenge here, like with the hominins, is to project paleoclimate studies to the present day as a probability map, based on how far back the world diverged from baseline. Given the option, I’ve erred on the side of making things interesting and diverse. There are some specific things I have to factor out. Most prominent are Milankovitch cycles, which depend on changes in Earth’s orbital eccentricity and position over time. This would violate the “no change in position or gravitation” condition I’ve set on paratime transpositions.
As for sea level figures, I really did specify:
The underlying correlation between temperature and sea level also comes from paleoclimatology. There is a lot of room for error, which is why I use GURPS Space style qualitative temperature bands rather than specifying an actual degree C. The correlation between sea level and hydrographic percentage is based on present-day bathymetry, but I think that’s reasonable enough for my purposes.
Yes, sea level is mostly effect rather than cause (ice coverage is a more important driver), but Traveller focuses on hydrographic percentage and sea level is how you get to that figure. It’s also helpful to visualize the coastlines in an alternate Earth, even if the divergence point isn’t far enough back for major continental adjustments.
So you did. I missed that because I was expecting to see m or yd or something in the table itself, either in the column head or in the entries (like “%” in the next column). I don’t habitually look at the preceding or following text when I’m reading a table; I just completely failed to see it.