Indeed, in terms of sudden impact and method of impact, no they are very different, and climate change probably won't go so far as to make the human race extinct, at least not for a very long time. However, whether or not it will be catastrophic for the human race within the next 100-200 years no-one can accurately predict, given we do not know how much we'll do to stop it before it's too late (bare in mind that some scientists already believe the tipping point beyond which we can no longer stop it is well upon us).

As mentioned, the collapse of farming may well undermine any efforts to stop climate change given the big knock on negative impact on the world economy. Though that could also save us as there'd be a sudden massive drop in fossil fuel use and carbon emissions in such a scenario. There's a lot of variables, but a catastrophic collapse is definitely a possibility. I think the human race is capable of saving itself from this, but capitalism and the corporate economy I fear stand in its way.