Thinking about what a non license pinball theme along the line of "Global Warming" would look like with features, and how the theme could be made a great, or at least a decent pinball machine. What could this theme incorporate?
A couple of features the game play could incorporate would be that you could choose the time of the Earth's existence and experience the gameplay based on the global conditions in the years, or era you select. What could be a new and unique "cool/hot feature" would be to heat/cool the metal flipper button guards depending if you were in a cold or hot Earthly condition and timeframe. Think of how the coolly cups can be heated and cooled in todays fancy nancy cars. Apply that to pinball here.
For the gameplay on a Global Warming Pinball Machine, maybe you start at the beginning of time and progress until the end of time with global fires or global freezing, or Val Hala, depending how you perform. The contrasting Winter Conditions and Summer Conditions of weather visuals could be accomplished as they did at the Olympics where the Chinese projected the images of boxes moving up and down on the stadium playfield, I believe, but it was spectacular imaging that could likely be done to change the Winter and Hot Summer seasons from a visual sense over the playfield. GOT does an okay job with Winter is Coming, but that could likely be made "top shelf" with more concentrated effort and projectors.
Maunder Minimum Multiball could be obtained in Year 1645 through 1715 and the Mini-Ice Age Mode will begin. Destroying Sun Spots with a manmade contraption designed by Rube Goldberg could be incorporated into the DMD video game. I could also see a spinning Sun (think WCS soccer ball) in the PF, and it could be internally LED lit to glow red or blue depending on where you are in the gameplay and what the Earths temperature is at that time.... Sun spots could be as red and orange flashers from inside the Sun playfield toy.
You could work in the Suns Temperature and the Earths Temperature in side by side displays on the backbox or PF. The displays could use these temps to control gameplay, strategies and goals.
The Industrial age could cast a visual smog over the PF as factories and societies across the World enter into the next phase of life on Earth. The 1960's and 70's could bring in the EPA and Clean Water and Air Acts, etc and the smog would be reduced significantly.
Wizard Opens up to the Garden of Eden, 20 Virgins, PHOF,or whatever you pre select as your desired ultimate goal and wish. This is what happens when you retire....LOL.