Do you ever give ice ages a thought?
Given a loose definition that ice ages are when the glaciers are advancing, rather than retreating, planets with close-to-earth climates will spend about half of their time in an ice age. Of course, I could be off with this, but it does have a certain binary logic to it.
The only other option that I can think of is that the global ice is always in stasis, rather than the dynamic environment of our world. This could be possible if the world is too warm for water to ever freeze, too cold for ice to ever melt, or if the glaciers somehow never move either way (by magic, precision environmental systems, or GM/designer laziness).
Ice ages need not be the viewed as massive sheets of ice covering the globe. For example, the "mini ice age" of the 1700’s saw an overall drop in temperature. Valleys can be gorged out, rivers and mountains created or destroyed, topsoil stripped from one area and enriched in another, and floods from melting ice can cause climactic and geographic changes of their own.
Climate changes from ice ages, even mini ones, cause changes in society as well. People being indoors more spreads disease from the close quarters. Invasions and other wars are less frequent and don’t last as long as they do in warmer times; the exception to this is when foodstocks run short in one area. Architecture changes too, such as more sharply angled roofs, fewer—and smaller—windows, large central fireplaces/warmers—or numerous smaller ones, and buildings tend to become more compact and boxier. Folk travel less when the weather is against them. This reduces tourism to almost nil, and slows the exchange of ideas, as well as goods. With lessened exposure to people in distant lands, languages become more locally distinct.
If interplanetary travel if possible, people have the option to travel off-world, or at least the potential exists. This can vastly alter a long timeline, as worlds come and go in power with their shifting environments.
I tend to think of ice ages only because they impact the maps I make. Taking them into consideration, only as the source of creating nifty geographic features.
What do you think?
Additional Ideas (2)
A place where everything is made of ice.
There are no trees. There are no rocks. There is only ice.
Imagine a place unchanged since the end of the Great Ice Age -
over 20,000 years ago.
A place where the mighty Woolly Mammoth might still roam!
Imagine a place where the sun shines every hour of every day -
for almost half of the year! Then - darkness for the rest of the year.
This is the home of the Throps - rulers of the long summer day.
This is the home of the Squallhoots - rulers of the long winter night.
This is Athropolis
Have you ever wanted to run a game in a world of perpetual winter? In a world of Ice and Snow? Did you tinker with it, then stop because you didn't know much about this kind of environment... and the setting didn't seem to have verisimiltude? Well here is the information you need.
The information could be used for a simple travel story arc as well.
Here is the information in easy to digest bits. Sure most of these sites are geared for kids. But you can breeze through the site's information and still get the important pieces you need to know to set up such an environment.
Web Site of the Throps and the Squallhoots ( and all things COLD, ICY and ARCTIC )
Image intense, but good for inspiration....
and of course
This is another good site for information about biomes and ecology in general
More Planetological information