J. R. R. Tolkien is the type specimen for good worldbuilding. He used his expertise in linguistics and medieval poetry to invent new languages, then built a world around those languages, then wrote stories in that world. I have always loved Tolkien and so he should have a place in my discussions of world building.

Unfortunately, Middle Earth does not fit the criteria I established in Part I. It does have an atmosphere, but it is not a sphere. The sun and moon are a fruit and a flower from the two trees that sail in ships across the sky. This is not a place where we would expect normal climate science to apply.

But the resulting climate ends up mostly making sense. If you understand enough about a few subjects, you often end up inadvertently learning some information about other subjects as well.

This is a multiple post series: I, II, III, IV, V.

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Prerequisites: Part I: A Sphere with an Atmosphere.

Originally Written: Spring 2022.

Confidence Level: The science is well established. The interpretations of the climates of Middle Earth are my own.

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The climates of many of the regions of Middle Earth are explicitly described in the text. Forests are shown on the map and feature prominently in the story. The Shire is a fertile land of fields and trees. Rohan is mostly grassland, the edge of a steppe that extends to the east between southern Mirkwood and Mordor. Harad, or at least the parts of Harad closest to Gondor, is a desert. We can use the climates described in the text to figure out what the larger scale climate patterns are.

When trying to understand a climate, some of the most useful things to figure out are the prevailing winds. In most places, the wind comes from one direction much more than from the other directions.

Consider a city on the coast, with the ocean to the west and mountains to the east. If the prevailing winds are from the west, the wind will usually bring moisture, and it will rain most of the time. If the prevailing winds are from the east, then the wind will usually be dry, coming down from the mountains. Seattle is an example of the first type of city, while Lima is an example of the second.

Based on the climate zones described by Tolkien and the locations of the oceans, we can figure out the directions of the prevailing winds of Middle Earth. Once we know these prevailing winds, we can use them to determine the climate of the regions not explicitly described by Tolkien.

In the northern parts of Middle Earth, the prevailing winds are from the west. The lands to the west of the Blue Mountains, Forlindon and Harlindon, would be temperate rain forests. The Blue Mountains are short and don’t have much of a rain shadow.^[1]I’ll describe what a rain shadow is below, in case you don’t already know. The lands to their east, including the Shire, have a climate similar to most of Europe or the eastern United States.^[2]In the Köppen classification, it would probably be humid continental or maritime, extending to humid subtropical in the South.

In the southern parts of Middle East, the prevailing winds are from the east. The winds in Harad come from inland, so most of this country is dry.

Gondor is in between, so it probably has a Mediterranean climate. It might have weak monsoons. There is even a little evidence for this in the test: the Lament for Boromir, intended to be remembered in Gondor, treats all four winds as equally common.^[3]The east wind is not part of the song, but the surrounding discussion makes it clear that it is present too.

There is one thing that I do not like about the climate zones of Middle Earth.

It is not Mordor. Mordor’s climate does not make much sense, but that is OK because of its role in the narrative. Sauron is a demi-god of geology who raised mountain ranges for walls around his kingdom and used a volcano as a forge. He clearly has the power to control nature on a large scale. If he wants to make Gorgoroth permanently shaded by volcanic ash and Nurn perfect for slave plantations, he can do that.

My complaint is Mirkwood.

The Misty Mountains are much taller than the Blue Mountains and they should have a significant rain shadow. Air has to go up to get over a mountain range. As it goes up, it cools. Cold air cannot hold as much moisture as warm air, so the humidity in the air condenses into clouds and rain or snow. The rain would fall on the western slopes of the Misty Mountains. The lands to the east of the Misty Mountains should only get a little rain.

Forests require a lot of water. Having very little rain is going to be a problem. Where does Mirkwood get its water from?

Lothlórien gets its water from snow melting at the tops of the Misty Mountains. Fangorn also gets water from snowmelt, and it can get some rain through the Gap of Rohan. But the water from Lothlórien and Fangorn flows south into the Great River and does not reach Mirkwood. I don’t think that Mirkwood gets its water from the Grey Mountains in the north either. There is no reason why these mountains would be particularly wet, and there is an uninhabited gap between the mountains and the forest.

And so we have a tall, dense forest, the largest in Middle Earth, with no significant water source. If I were retelling a story from Middle Earth, in film or another medium, I would turn Mirkwood into a desert forest.

The ground is thick with tangled and thorny shrubs, but the taller plants are too sparse to provide real shade. The few streams you find are strange colors due to unknown minerals or maybe magic. What a place for giant spiders !