The planet I am currently creating has a set of rings composed of iron dense rock, and other materials scattered throughout. The objects in the ring average about 20mm to 10in. I am wondering, how would this affect the climate? For some extra info, the land is mostly desert with bits of rainforest areas next to the ocean. 2/3 of the surface is water (A bit less than earth) the rest being land. The planet is at a 26-degree tilt, the rings have the same tilt. The rings are low density so light can mostly pass through.
In reality, they would have very little effect
Rings are generally much less dense than you might think. We see lovely images of, for example, Saturn that looks like the rings are almost solid, but they're not. Images of shadows on Saturn itself look really dark — but remember just how far away from the planet the camera was.
Will there be shadows? Yes. But as Saturn's unusually broad rings demonstrate, the ring shadow will be quite narrow and in reality, much less "black" than one might suppose. Remember too, the more you tilt the planet to get a wider shadow, the more you're pushing the shadow toward a pole and, eventually, off the plane of the planet entirely.
Would the shadow nonetheless effect climate? Sure! Anything that shadows light will cause differences in temperature that will generate everything from winds to storms. How much of an effect this would actually have is incredibly complex as it can't simply be, well, simplified. Just a few of the major (much less minor) variables involved include the type of star, size of the planet, distance of said planet from the sun, axis angle, orbital obliqueness, speed of rotation, speed of the orbit, size of the rings, material the rings are made of ("rocks" is meaningless, what type of rocks? what minerals or chemicals? what min/avg/max size?), density of the rings, distance of the inner- and outer-rings from the planet, size and location of oceans, size and location of major mountain ranges, size and types of dirt on major land masses, constituency of the atmosphere... and that's just for starters... and you haven't provided almost none of that data to the detail required for a thorough answer.
We're here to help you create and consistently use the rules governing a fictional world of your own creation. It's often easier to ask how to rationalize the effect you want than to ask what effect would result from the cause you want. But in the end, it's much easier to design the rings you want and then arbitrarily decide what effect those rings will have on your climate — and move forward. It's breathtaking just how much work is involved to create what someone might call "realistic" weather.
If you want a more specific answer, look back on the list I provided and start giving details. Specific details, some of which will be maps.
Angles matter for seasons, mostly winter season
Difficult to predict, you would need more data - and a specialist - to calculate it!
The density of your rings is important, of course.. And the diameters of the planet and its rings.
The effect on the season can be explained: that will depend on the angles, and where you are on the planet.
Orbit inclination angle, planetary axis tilt angle
At certain angles (and certain seasons!), more of the sunlight would get blocked.
If angles are large, the affected part of the planet would be larger, but the effect would be less. Seen from atop, these rings are not so dense. And it would heavily depend on the seasons ! A certain band below, or above the equator would not get sunlight, or only part of the sunlight, during winter. In summertime, you'd "look over the rings" and see the sun. In winter time, you'd look through the rings.
If both angles are small, you won't have prominent seasons, but you'll end up with a region around your equator becoming quite dark (sunlight has to penetrate much more rock cloud !)
Axis angle and seasons
In summer season for the northern hemisphere, the axis angle is toward the sun, the rings would be visible on the horizon or not visible, with the sun above the rings band. In winter season on the northern hemisphere, the axis angle is pointing away from the sun, you'd get the rings to block sunlight, a colder winter.
Effects when looking up in the sky
The larger the angles, the more variation you'll see. The rings look like a band that extends over the horizon, the sun is above or below that thing. How dense and wide the band is, also depends on the diameters..
There's an hour of Youtube explaining how you could simulate this kind of stuff in games,
The only way I can imagine planetary rings influencing climate is by blocking light from the host star. Less sunlight means lower temperatures, which can have a whole bunch of complicated effects across the globe. The most efficient way to block light from the star would be to have the rings angled relative to the planet's orbit. The greater the angle, the more light is blocked:
Assuming the planet orbits around an axis approximately perpendicular to the ring's plane (e.g. the planet is not Uranis-like), this means the pole orientated away from the star would also be shaded by the rings.
The angle of the rings is not the only variable we have to play around with. If the rings had a small angle, but the rings were very dense (i.e. the proportion of the volume of a ring taken up by material is high), they would block light from reaching the equatorial region. I couldn't find an estimate on the maximum density of a planetary ring system, so I can't give you any hard numbers describing the situation.
However, there are a few pictures showing the rings of Saturn casting a very solid looking shadow on the planet. The accepted answer to this post uses these images as evidence almost no sunlight can get though the rings. I am skeptical of that claim because photos taken from several thousands kilometers away tend to have less precise details. It is completely possible that from the surface there is still a moderate amount of sunlight available even though out photos do show complete shadow. Still, there is no denying that the amount of available sunlight would be decreased.
There is one last factor to consider: the width of the rings. If the rings were in the same plane as the planet-star system, sunlight attempting to move though the rings would have to get though the entire wide of the rings. However, as the angle of the rings increase, the distance the light has to travel though the rings decreases.
Overall, we have 4 effects. I expect this is the order of how large an impact the effects will have on the climate, but honestly that is a complete guess on my part:
- As the angle of the rings increase, the shadow of the rings moves toward the poles.
- As the angle of the rings increase, the amount of surface area on the planet covered by the shadow increases.
- As the density of the rings increase, the probability of a ray of sunlight traveling though the rings will reach the planet decreases.
- As the angle of the rings increases, the probability of the of a ray of sunlight traveling though the rings will reach the planet decreases.