Yes it is. Much much faster.

There are several reasons, among which (the list is not exhaustive):

• Many positive (and negative, but the overwhelming effect is definitely positive) feedback processes are known to exist, but cannot be quantified. If they cannot be quantified, they are not taken into account into the models, only as vague “climate tripwires” with no certainty of when the trigger will be pushed or in some cases if it has or hasn’t already. Some of those have the potential to rival human emissions in scale if we do trigger them.
• Many other similar feedback processes likely exist but we are not even aware of them.
• The source of governmental decisions is the IPCC; when an IPCC report is published, the research it uses is already years, sometime more than a decade, out of date (this makes sense but it does mean there is a lag between current reality and decision-making).
• The IPCC report itself, once actual scientists have finished writing it, is then provided to political actors (the US, the UAE, etc.) in order to reword or rewrite parts of it they deem incompatible with their strategic objectives. There was a leak of the politically-unedited IPCC report about two years back, and the wording was very different.
• Many scientists self censor, consciously or not, because they’ll usually end up being called “alarmists”. This, among other things, results in the models the IPCC designs and uses being highly optimistic.

As a sidenote, and only somewhat related to your initial question: for a few years now, all IPCC trajectories that do not end up in widespread societal collapse and potentially human extinction rely on imaginary technologies.