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Bear with me, this is my first Meta Question.

When Building your fictional magical, alien, alternate fictional world, you have to figure out the Climate (unless you only interested in one region and then the rest can go fly a kite for all you care!). Unfortunately it's not as simple as create a map and then see what happens. If it were, we would have a much better understanding of our own climate.

You research, and then you research some more. You have taken hours and weeks, possibly months or even years, of time to research 'everything', and you have attempted to put it all together. You start building your story based on this map and understanding but then you suddenly think! "Wait, does the wind really blow like that?", "will there really be that freak weather storm?", "can I really have this next to that?". Doubts starts to creep in. And doubt breeds more doubt. You need a second opinion! You possibly even decided you needed a second opinion before you developed your story too far.

Unfortunately for you, all the scientists are too busy trying to understand our own world and don't have a lot of time to discuss fictional settings that won't result in papers being published. So you turn to the next best thing. The Internet. You find a forum of like-minded people who don't shun you for asking silly light-hearted questions like "How do you kill a Dragon Zombie?", they respond with more than "What on Earth are you talking about?" and you don't have to explain for the umpteenth time "This scenario is not on Earth! or our Earth!".

You know that climate is very complicated and if you ask everything at once, people either won't know what to answer or focus on the wrong things...there are just too many possible answers. But you have a whole world to question! Sensibly you separate your entire world of questions down to several 'specific' regions and features. This is not about asking what will happen if you raise a mountain etc. You have already done that research, you just need an assessment of your interpretation. Is it, or is it not plausible.

Besides, where would all the fun be if you could just straight out ask what happens if I have a huge hole in the Earth? The fun (sometimes painful fun) is in figuring it yourself. The most painful part seems to be asking for opinions on your assessments.

What is the minimum amount of world and climate related information that has to be provided to avoid a climate question being closed as too broad? What information would help narrow down the scope of the question? Limit the number of ambiguities?

I'm trying to compile a list of information that needs to be provided before a climate related world building assessment can be undertaken successfully. I am very much aware that the climate is intricate and complicated and and and and...

For example, I'm not looking for a detailed description of how the wind will flow down that wonky shaped valley, and cause a negative feedback loop on this or that feature and make the farmer two valleys across have a thunderstorm. I'm thinking of more broad and general continent scale assessments. High pressure should form there, low over there, wind will flow in that direction, oh mountain blocking that direction flow...got a cloud pile-up. rain and river flow back in that direction. general environment conclusion. Desert highly unlikely, savannah plausible but more likely to be a temperate rainforest.

  • ... should all the separate regional questions be asked at once or wait for one region to be judged plausible/implausible before moving onto another?
  • ... should all the separate questions be hyperlinked, so readers can scan neighbouring regions?

You are providing the scenario to the reader, you are wanting an assessment of the accuracy/plausibility of your scenario from the reader.

  • I assume you will have to provide a map of the region in question or at least a fairly descriptive description.
  • I personally would need a more general map of a larger area, if not the world, to see the inter-relatedness.
  • where any prevailing winds are coming from
  • where any water is coming from, especially if not reliant on atmospheric moisture
  • If based on an alternate Earth, what are the differences locally AND regionally
  • If based on a new world, are there any similarities with Earth to help the reader understand the environment
  • ...
  • ...
  • a summary of what you think will happen
  • a summary of what you really really need/want/can't bear without to happen
  • ...
  • ...
  • a willingness to accept criticism
  • an openness to accept solutions

Am I forgetting anything? What else is needed? or are we just on our own when it comes to anything climate related?

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  • $\begingroup$ Thanks for moving it! Also I realized I sounded very formal/cold with my comment on your other posting. If I came across this way I didn't mean to. I'm not qualified to answer this question, but I hope you get the attention you're seeking! $\endgroup$ – Ranger Aug 24 '16 at 22:32
  • $\begingroup$ no worries, I had thought it might be a meta question but was a bit daunted at asking a 'protocol' question! see second opinions help! :) $\endgroup$ – EveryBitHelps Aug 24 '16 at 22:34
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    $\begingroup$ To be honest, I believe that some people vote to close climate questions because they are not knowledge enough and think it's not answerable. $\endgroup$ – Vincent Aug 24 '16 at 22:49
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    $\begingroup$ Also, the climate questions that do get closed tend to have other flaws. $\endgroup$ – Vincent Aug 24 '16 at 22:52
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    $\begingroup$ Welcome to meta, and thank you for asking this. Finding the right balance point -- enough to be answerable and not so much as to be overwhelming -- can be difficult. I hope our users who are more knowledgable about climate can offer some practical advice. $\endgroup$ – Monica Cellio Aug 25 '16 at 0:42
  • $\begingroup$ I may point you to the Creating a Realistic World Series, and in particular to the part about climate as they may help you get started on the process. $\endgroup$ – clem steredenn Aug 25 '16 at 12:36
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    $\begingroup$ Definitely a good question, but I think this article on the blog may be relevant here. $\endgroup$ – Frostfyre Aug 25 '16 at 14:02
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    $\begingroup$ Oh, I have no problem getting started. I have a masters on oceanography. What I am wanting is a defined list of what people should add in their question so that their question isn't put on hold as too broad a few hours later. $\endgroup$ – EveryBitHelps Aug 25 '16 at 17:18
  • $\begingroup$ But I have found all the step by step guides and posts helpful in keeping track of everything, and creating a sensible order to the worldbuilding process $\endgroup$ – EveryBitHelps Aug 25 '16 at 17:26
  • $\begingroup$ @frostfyre, did you really buy a custom made table for your drainage basin? 😂 $\endgroup$ – EveryBitHelps Aug 27 '16 at 8:59
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    $\begingroup$ I didn't. That would be too far, after all. $\endgroup$ – Frostfyre Aug 27 '16 at 13:29
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Climate is a difficult point to answer, precisely because it's very broad in nature. But climates in various regions are also interconnected; it's obvious (hopefully) that you won't have jungles anywhere near ice caps.

As for the minimum necessary information, that depends to some degree on the scope of the question. "Climate of this fictional planet" is broad, but might actually be easier to answer than "climate of this particular region of this fictional planet". I know that probably sounds nuts, but the former would presumably come with a world map; people asking the latter tend to provide only a regional map, where an accurate picture of climate requires more than that.

For any climate question, some assumptions have to be made. If you go too far from Earth-like (an atmosphere with 80% oxygen and 20% sulfur, 3G or 0.5G gravity, 300-hour day or 4000-day year, binary star system, etc.), that's probably not going to be answerable with the knowledge base at hand. So, assuming a planet at least somewhat Earth-like, the minimum is:

  • A map of the entire planet, one that shows at least basic divisions in altitudes (deep sea/sea/land/plateau/mountains would be a minimum: marking 1000m divisions would be ideal). If only a regional map is available, marking latitude lines correctly is absolutely vital for accuracy: climates near the equator will produce massive differences compared to climates at 50N.
    • I recommend not using a Mercator projection for the map, due to its inability to show the poles. Equirectangular would be best, due to its simplicity and ease of conversion to other projections, but something like a Hammer equal-area projection would also be usable.
  • If the planet is not "Earth with different geography", some astronomical details will become critical to judge temperature accurately:
    • Stellar luminosity and orbital distance between the planet and its star. For a near-circular orbit, the solar constant (for Earth, this is about 1367 W/km2) will suffice.
      • For a non-trivially eccentric orbit, the solar constant will not be constant over the course of the year; it is effectively an average of incoming solar radiation, a ratio of luminosity versus distance, but an eccentric orbit will produce sufficient variation over the course of the planet's year that an average will not properly reflect planetary conditions.
    • Axial tilt is critical, as this is what determines the seasons. A planet with no tilt has no seasons, while a steep tilt produces wildly differing seasons. Earth's tilt is about 23 degrees; more than 45 degrees or so, and you're probably not going to get rational results when trying to determine its climate (no Uranus-style tilts, please).
      • For a non-trivially eccentric orbit, you will also need to know the times of perihelion and aphelion (when the planet is closest to/farthest from the star) in relation to the seasons; if perihelion is near the height of the northern summer, for instance, then the northern hemisphere will have noticeably greater seasonal variations than the south. Due to axial precession, that relation will not remain constant over geological scales; Earth, for example, goes through a complete precession cycle over about 25,000 years. Applied to a fictional planet, that means that perihelion would be during the southern summer (instead of the northern) about ten or fifteen thousand years from whenever "now" is, which is something to keep in mind.
    • Bond albedo (not geometric albedo, that's something different) and emissivity of the planet. The former is basically the average reflectivity of the surface, whereas emissivity here is referring to the planet's emission of thermal energy; the greenhouse gas effect works due to energy being reflected back to the surface when emitted, which would lower emissivity. Both are 0-1 ranges (higher values indicate more energy loss, which here means a cooler planet). For Earth, these are about 0.3 and 0.612, respectively.
      • This is rather advanced stuff; unless explicitly noted, this is probably Earth-like.

To use those parameters, here's a Wikipedia page with the necessary formula. I've posted that formula below, where (Sc) is the solar constant and (a) is bond albedo. $\frac{A_{abs}}{A_{rad}}$ is a ratio connected to the planet's rotation; for anything near an Earth-length day, this is assumed to be $\frac{1}{4}$ (a very slow rotator or a tidally locked planet will be closer to $\frac{1}{2}$, but at that point it's probably straying too far from Earth-like for an accurate prediction of climate). $\sigma$ is the Stefan-Boltzmann constant ($5.670373 \times 10^-8$), and $\epsilon$ is emissivity: $$ T = (\frac{A_{abs}}{A_{rad}} \times \frac{Sc(1 - a)}{\sigma\epsilon})^\frac{1}{4} $$ And here, I give the equation for the solar constant. L is luminosity of the star, while D is the orbital distance between planet and star. Despite the name, this is only truly constant in a circular orbit; in an eccentric orbit, this figure will vary over the course of a year. $$ Sc = \frac{L}{4\pi D^2} $$ You should get a result of about 288K (15C) when plugging in Earth's figures: this is basically an average taken over the planet's surface. If the fictional planet's characteristics result in a different surface temperature, that's going to have an impact on climates. If the orbit is non-trivially eccentric, you'll have to run through the formula twice (perihelion and aphelion).

That's only the minimum information. This next list is stuff that should be provided by the person asking the question if practical (although they're probably asking the question because they don't know how to figure out all these steps), but which is possible (if likely time-consuming) to calculate on one's own as part of an answer:

  • A map of the ocean currents.
  • Summer/winter maps of wind patterns and high/low pressure zones.
  • Summer/winter maps of precipitation.
  • Summer/winter maps of temperature.

I've posted guides to climates before in answers. This answer in particular has me describing in detail how to calculate everything in the second list and make a climate map from the results, given a good elevation map; as posted, it's limited to "Earth with different geography", but someone willing to modify the temperature guides can make it work even with different astronomical parameters. From there, it's not hard to make the step to biomes if desired. I also tear apart a user's map here, outlining some problems with their climates; it's basically an example of what not to do in a climate question (incomplete map, no latitude lines, not even a defined map projection in use), because the lack of information meant I had to rely on guesswork for a lot of that answer.

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I'm not sure I qualify as knowledgeable, but I would not like to leave that question unanswered.

So, you mentioned it a few times, but I don't think it ca be said too much. Climate is a very complex thing.

A world is usually way too large, so asking how is the climate of my world will probably be closed as too broad. So you should limit yourself to a region. A continent has many different climates, so that would still be too large. But a given region might become answerable.

As for technical requirements, I think that on a rough scale, the climate of a given region will depend on

  • Intensity of light from the star(s). This could be inferred from the size/activity of the star, distance to the planet, and inclination of said planet.
  • Map, water bodies, size, mountains ranges, etc.
  • Global currents, that might be due to ignorance, but if we can see the effects the currents like the Gulf Stream have on the climate, I haven't seen any explanation as to why those currents were as they were.

For me, with those information, people might start to get a rough idea of how the climate in a given region might be. Note that the map and global currents should also include larger regions. Europe has relatively mild winters due to the Gulf Stream bringing heat from the Carribbean and mountains blocking the worst of the the Siberian winds.

Now it comes down to the level of precision you want to have.

If you want to have a measure of the area of a circle to a thousands decimal precision, you need to make sure that both your radius and pi are taken with the same precision or above.

Similarly, you'd need to consider the composition of the atmosphere, the type of rock/grounds, the Human activity, etc. to get a more specific answer.


Conclusion, if you want an answer like:

  • Yeah it's mostly warm, but with some rains, little details are required.
  • The western part will have an oceanic climate, while the rest will get a humid jungle you probably have to make sure that the 3 points I mentioned above are covered.
  • In that area, you'll have winters with temperature varying from 5-15°C, and summers from 20-35°C, with regular rains throughout. A few storms in Winter, and the vegetation is likely to be composed of that tree and that other tree. Do make sure you added the extra details.
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