One point is on the effects of warmer temperatures on the world's separated climates. If global warming is occurring, the colder parts of the world will get warmer, and the warm areas will get hotter. For example, the freezing temperatures of northern Canada will become more temperate, even as the warm temperatures of Florida will become harsh and desert-like. This will cause plants, animal, and humans, all of which are evolved to live in certain climates, to die out. However, assuming this shift is not extreme in a short period, the warming will also cause fewer cold-related deaths in cold environments; additionally, cold environments could become fertile farmland as temperature and rainfall increase.
Another point is that the ocean temperatures could rise. This could harm fragile ocean life, such as coral, while requires a specific average temperature; many rare species of coral could die out, causing the ecosystem that lives around coral reefs to move or become extinct.
Other important points include the effects of politics on science, the notion that rising temperatures could affect global climates, the possibility of extreme weather (unproven thus far), the potential for increased plant life in desert environments (which would add to overall CO2 locking), and the potential for transforming previously uninhabitable environments such as deserts.