Think of climate change like a car driving off a cliff. The car is “safely” on solid ground until it isn’t. The problem is that at some point to avoid the emergency you need to hit the brakes or turn, and this particular car might not be able to turn or brake very hard without catastrophic effects on the occupants. Moving away from this metaphor, there is a possibility we cross a tipping point in the climate system (and may already have done so) that can be “reversed” through emergency geoengineering: but it’s not clear that the necessary level of intervention would be compatible with global agriculture and civilization.