Sounds like I need to revive an old thread. In response to questions about "what does global warming do?", and common misinformation about its effects, I would refer readers to the following thread:
http://forums.civfanatics.com/showthread.php?p=2014915#post2014915
To summarize:
1. Nothing can reduce global warming.
2. If you forest a tile, it will "absorb" global warming effects by giving the game one more forested tile to deforest--but it won't reduce the rate at which tiles become deforested.
3. Deforestation (e.g., Jungle and Forest reverting to base tile) and Grasslands-to-Plains are the only DEFAULT global warming effects currently functioning in the game. [Edit: added the word "DEFAULT" here for clarification. Other transformations also work (see the link above), but are not coded into the default .biq file.]
4. Although the default .biq file is coded for changing Plains-to-Desert and Marsh-to-Coast, these transformations are broken. They no longer work, due to one of the patches that was issued (not sure which one). Ask Firaxis about it, because I consider this to be a major loss for late-game effects.
Nice thermometer, Pounder. I like it.