You're playing a silly game by trying to make me state there is some "ideal" way the world "should" work, since everyone here knows the world isn't designed for anything. I can just as well demand you tell me what the ideal rate of change in temperature is. Note that you can't dodge that with "whatever the rate of temperature change would be if we enacted no policies", because there's no particular reason to think that whatever that exact amount is isn't too high (or too low!).

The point is that current levels of climate emissions are much costlier and deadlier than a world where (good) policies have been enacted to decrease the flow of carbon into the atmosphere.

Just to throw it out there, though, I'd suggest a guaranteed change of 2F/century would be greeted with an instant acceptance and sigh of relief by everyone.

The change from the last ice age to the current climate took thousands of years. It was still fast enough to eradicate a good chunk of ecosphere. The change we're causing will happen at least ten times faster.

That depends on what you would deem acceptable "impact" to our existing ecosystems.

> What’s the ideal rate then at what temperatures should change?

Ideal for what goal?

many times slower than it is now. The answer is of little relevancy because every single plan we have for reducing this rate either doesn't reduce it enough or only barely does so.