Worldbuilding 1c: Climate

This post is part of a series on worldbuilding; links for the whole series can be found on this page.

Some readers have adroitly grasped that I've tried to slip the reader a fast one.  Yes, I'm saying your game world should be a sphere exactly the size of Earth.  I'll go one better and recommend that it has a yellow sun, that it's 93 million miles from it — and even that it should have a single large moon, and just one.  Why this inflexibility?  Why am I dead-set against the reader making a really imaginative, unique world instead of just another version of this tiresome old orb?

Because we have exactly one template on which to base a world.  We don't even know if life as we know it can exist on a planet without a yellow star; or without any of the other characteristics this world has.  We have no evidence that it can.  But more importantly, what difference would it make?  No one argues that some other bizarre unique differently sized, tilted world with green rainfall and so on won't have human beings living on it, which coincidentally are the same size we are, with the same biology, the same brains, the same motives and the same social characteristics.  So why should it matter how big the planet is?  The players won't care.  No player anywhere will learn that your globe happens to be 7,926 miles in diameter and shout, "WHAT!  Why, that's the same size as the Earth!  I'm quitting this run of the mill, uninventive campaign!  The very idea!  Shame, you DM you, shame!"

When I advise not to waste time caring about things that don't matter, THIS sort of thing is what I mean.  Create a smattering of continents and islands on the blank template of the earth's surface, be glad you have it as a template to work from, and move forward.  There's a lot to do.

Why does "climate" come next?  To begin with, we're not speaking of "weather."  People tend to treat them interchangably, getting them mixed up.  By "climate," I'm describing the system of physical air, or gas, that surrounds the globe to a sufficient depth to provide life and protect it from the central star's radiation.  None of this, of course, need ever be mentioned to the players; and none of it needs to be described and written down for your game world!  But we must have climate in your mind in order to lay out the coastlines and the topography, if the lands and the civilisations living on them are to make any sense.  Bear with me, and I'll explain why.

The game world — and most likely every solid body in the universe large enough to support life — has four liquid systems that flow with continuous, unrelenting motion.  Some of this motion is incomprehensibly slow, at a speed of less than an inch a year.  Some is terrifyingly fast, fast enough to blast mountains apart, or scour the land at speeds above 150 miles per hour.  Scientifically, these four systems are called the athenosphere (magma), the lithosphere (crust), the hydrosphere (water) and the atmosphere (air).  Of these, the one with the greatest volatility, the greatest constant presence, and the most immediate relationship with us, is the last — and thus, "climate."

Imagine that we could pour the air into a series of bowls on a table, each bowl of different size.  We'd have tiny little bowls an inch in diameter, and great big bowls that are a full two feet wide.  We fill them with air, then we move the bowls around until every space on the table is nearly full.

Now imagine that some bowls are taller than others, and that as the air of one bowl overflows its brim, it pours into an adjacent bowl.  The largest bowls are the lowest; the smallest bowls are the highest.  As we pour air into the smallest bowls, we watch it wind its way from bowl to bowl, drifting downwards just as though we were filling the bowls with water and watching it flow.  Remember, air is still just a liquid, though with much more kinetic energy than water.  Imaginatively, we can scoop air out of the biggest bowls and pour it into the others, forming different currents as the air flows around, until it reaches the bottom.

Suppose we take a hot plate and put it under the large bowls in the middle of the table.  Then we freeze the bowls at the top and the bottom of the table.  Now we can watch the air in the warmer bowls expand and flow upwards.  We can watch the air in the ice cold bowls contract and thicken.  We can freeze the smaller, highest bowls too, and watch the cooler air flowing down to it meets the hot air flowing up.  Got all this in your mind?  Jumping ahead because you see where I'm going?

Topographically, the largest "bowls" are oceans and seas; the smallest are glaciers and very deep lakes.  The warmest are also oceans and seas at the equator, while the coldest are ice-capped continents and frozen seas at the poles.  The "rims" of our bowls represent boundaries between vast plains, plateaus and valleys, or the coastlines between water and land.  The lines we draw that divides each part of the topography also creates a "bowl" of air, which interacts with other bowls around it in unique and interesting ways, as air from one part of our game world flows this way and that into other parts.

This is made more complex by the changing of day into night, and the changing of winter into summer.  As continents heat up during summer months, the pools of air above those continents becomes warmer than the air over the oceans and seas, reversing the dynamics of flow on a grand scale — with small scale reversals changing with night and day as the same continent cools at night and heats up during the day.  In the winter, those continents freeze, turning colder than the oceans, drawing air in and becoming less dynamic as energy (with the cold) drains from each molecule of air.

Okay.

So why care?

Am I asking you to systematically design a climatic scheme for your game world?  No.  No, I'm not.  I'm saying that, like I've said already, being aware of these things makes it possible for us to decide later on, ten or twenty years down the road, that if we want to add notes about climate or, gawd forbid, weather, we don't have to say then, "Oh jeez, why was I so stupid about the way I placed my continents, mountain ranges and deserts?"  Such as any person must be when faced with Greyhawk's ridiculous assemblage of irrational topography and vegetation.

Look.  Climate is important.  Climate dictates what we can grow and eat, what we wear, what shelters we live in, what people do for a living, the state of health, the presence of water and what bugs are in it — and therefore the practicality of possessing property, which fundamentally is defined by water use.  All that defines the bottom two levels of Maslow's hierarchy of needs right there.  And though we may not want to think of it after we make the world and place the continents and bodies of water, we should give it a two-second think before scratching out where the coastlines are and how high the mountains are.  That's all I'm saying.  Address the matter with some rhyme and reason, and then forget it as long as you want, knowing that when the day comes that you might actually care, the foundation is set in place logically.

The same can be argued about the hydrosphere.  Really big oceans get really warm at the equator ... which infuses the atmosphere with LOTS of energy, that has to go somewhere.  In the Indian Ocean, cyclones spawn in the Bay of Bengal and the Arabian Sea, pushed northwest by the southern trade winds, ramming into the northern trade winds and being deflected in all sorts of ways into India and Burma.  Here, I'll provide a map of winds produced by the world's coriolus effect:

In the Atlantic, hurricanes form on the equator between Africa and South America, drift north into the northern trades and then either smash into the Caribbean or the American East Coast, or spin round in the circle of the North Atlantic.  Pacific hurricanes form all along the equator from South America to the Philippines, drifting north into Central America or getting pushed west by the northern trades.

IF your game world is a sphere, and IF it has an atmosphere, and there are oceans enough to allow sufficient plant growth on the land, hurricanes WILL form in similar areas of your game world and move in the exact same patterns ... because the trades and westerlies occur because of the planet's spin.  They are physical manifestations occurring in a system driven by fluids and heat — both of which must exist in our game world, or else nothing lives in our game world.  We need heat also; we need to breathe; we eat plants that have adapted to this system of air movement and heat, which arises from the formation of the planet and the existence of a star to revolve around.  These things are not optional in your game world.

Your only two choices are to be ignorant of them, pretending they don't exist, and then what does that say about you as an intelligent being ... or to make good use of them, because they provide substance, depth, a familiar immersive experience for the player and a guideline for placing everything else that your game world includes.  Ignoring them sounds "easier" ... and it is.  It is easy to hammer two bits of wood together and call it a "gun" ... but it's not a gun.  It's harder to make a gun.  But a made gun actually functions as one.

I'm going to continue with this lecture; but as I don't want to write a book (you can read hundreds of them), what I'll say from here forward is deliberately simplified ... so please don't bother to quibble with me.  You'll only be telling me things I already know.

The map above helps give a sense of "macro-climates."  Take a moment and look at South America, with which likely the reader has only a passing understanding.  I'll expand the map, as some people can't find South America on a map.

We have three macroclimates in place.  At the top, the yellow northern trades come across the Atlantic Ocean and strike at the coast of Venezuela and the three states of "Guiana," as that coast was once called.  The brown southern trades flow into Brazil, on the right side, the east side, of the continent.  And the blue westerlies roll over Chile into Argentina at the bottom.

The Andes Mountains, not shown, run down the left side, the west side, of the continent, from top to bottom.  That blue arrow that's shown turning away from South America?  That's the westerly hitting the Andes and being diverted north.  The Andes are really, really high, and in some places wide and vast.  My goal here is to explain how the Andes interact with these three macroclimates.

The yellow trades hit Venezuela obliquely, at their southern edge.  Between the yellow and brown trades there's a region called the "doldrums," the Intertropical Convergence Zone.  Our game world has one.  It's an area of monotonous windless weather ... perfect for warm water to sit still under a hot sun and be turned into a hurricane.  The trades hitting Venezuela are just barely above this; when these same winds flow over the Netherlands Antilles, just north of Venezuela, they produce heavy strong winds that blow like crazy, especially in June, producing trees that look like this:

Which is why we don't want to go to Aruba or Curacao in the off season.  Just to the south, this same trade wind deflects along the coast, or up into the Orinoco valley (which has a microclimate, a much smaller "bowl"), until it skirts the continent or strikes the eastern slope of the Andes in Colombia ... where the water collected by the trades from the Atlantic is dumped, producing a humid subtropical climate.

The other side of Colombia sits in the doldrums, where the tropical heat on its coast produces convective rain that falls year round ... and during hurricane season, some higher elevations experience monsoons.  It's also a microclimate.

Look at the map again.  The brown southern trade winds roll over Brazil, bringing lots of warm wet rain that it pours all over the vast plain of the country, forming the immense Amazon rain forest.  The northern forest has some characteristics like western Colombia, as part of it also falls within the doldrums ... but the southern Amazon, where the continent is larger, just gets hot under the continuous, year round sun.  Remember what I said about land heating up and becoming warmer than the ocean?  The central Amazon creates its own humid climate, benefiting froma great deal of ground and surface water, a forest that stabilizes that water and the three trade winds that feed the steady high (warm, thickly piled, energetic air) that sits over the jungle.

However, the southern trades do get all the way across South America, again striking the Andes, dropping the very last of their humidity ... creating a desert coastal strip on the west side of South America that runs down Peru and into Chile.  The Atacama Desert in north Chile is one of the driest in the world, but it's very small.  There's very little land between the Andes and the Pacific Ocean, but it's very dry.  This is why the Incas lived in the mountains, and not on the coast.

Contrariwise, however, just to the south, the wet westerlies pour across the Pacific and meet the Andes in Chile.  That one divergent wind is deflected (so the Atacama gets none of these wet westerly winds), but the remainder dump huge amounts of cold, wet water onto Chile ... similar to how the westerlies in North America rain similarly on Oregon, Washington and British Columbia.

Therefore, on the east side of the Andes, in Argentina, the land is quite dry.  Not dry in the way of the Atacama Desert, which is further north and therefore gets more hot sun, but dry in the way of Alberta, Colorado and Texas.  It's perfect land for raising cattle, which the Spanish began to do enthusiastically in the 16th century ... thus creating traditions of the Pampas and the Gaucho.

From this patient description, the reader should get some idea of how the movement of different winds, at different latitudes, produce unique pools and parcels of air, that produce conditions of unique measure under which humans must endeavour to live.  Even the smallest amount of consideration granted to these characteristics of prevailing winds, topography and latitude — defining the amount of sun, or heat, which in turn defines the volatility of the "bowl" of atmosphere — gives us some basic understanding of how climate might according to a completely fictional continent, with shapes, topography and position different from the South American example.  Understanding, likewise, how these winds effect North America, Eurasia or Australia helps the worldbuilder design a characteristic, believable climate for his or her game world.

It goes one better.  It lets us decide where that mountain range on that fictional continent can be placed, to create the macro and micro climates that suit us.  Each mountain spur, each ridge, each massive lake dropped into the continent, creates unique characteristics that we can play off, while giving our game world both of continuity AND personality.