From Nature

After our fossil fuel blow-out, how long will the CO₂ hangover last? And what about the global fever that comes along with it?

“Because of this long CO₂ lifetime, we cannot solve the climate problem by slowing down emissions by 20% or 50% or even 80%. It does not matter much whether the CO₂ is emitted this year, next year, or several years from now [….] Instead … we must identify a portion of the fossil fuels that will be left in the ground, or captured upon emission and put back into the ground.”

“It is a little bit scary, if you think about all the concerns we have about radioactive wastes produced by nuclear power. The potential impacts from emitting CO₂ to the atmosphere are even longer than that.” But there’s still hope for avoiding these long-term effects if technologies that are now on the drawing board can be scaled up affordably. “If civilization was able to develop ways of scrubbing CO₂ out of the atmosphere, […]it’s possible you could reverse this CO₂ hangover.”

From Azimuth, where you will find lots of other graphs, numbers, and commentary, e.g.

But anyway: if we keep up “business as usual”, it’s easy to imagine us doubling the carbon dioxide sometime this century, so we need to ask: what would a world 3 °C warmer be like?
….
You can get some idea from the National Research Council report. … I think it’s important to read these [conclusions], to see that bad things will happen, but the world will not end. Psychologically, it’s easy to avoid taking action if you think there’s no problem — but it’s also easy if you think you’re doomed and there’s no point.

Which is followed a discussion of current trends toward those conclusions.