Yes, 98-2012 period was unexpected - for some unknown reason atmospheric heating got uncoupled from the ocean heating. So Antarctic melting intensified and Arctic ice loss skyrocketed while the general air temperature growth slowed (it has NOT stopped). The last couple of years the coupling has returned with a vengeance and we'll all be seeing its results soonish.
So yes, if you want to nitpick IPCC then you should provide context and full information. Not just convenient sound bites.
The bigger nitpick should obviously be that getting one thing wrong is in absolutely no way evidence for the GP's boldly false claim that nobody has gotten ANYTHING right.
A more important point is that temperature is just a proxy measure of the actual greenhouse effect of increasing energy within the climate. Temperature, as the 'hiatus' demonstrates, is also very dependent on the oceans and how much energy they are absorbing or releasing in a particular time frame. The IPCC notes in this section that:
Satellite records of top of the atmosphere radiation fluxes have been substantially extended since AR4, and it is unlikely that significant trends exist in global and tropical radiation budgets since 2000.
Meaning that we've been taking in more energy than we are dumping out at an unchanged rate since 2000, so the overall greenhouse effect never slowed even though temperatures did. You've already mentioned some of the speculated reasons for this, but the general simplistic consensus is that if the energy wasn't heating the air the oceans obviously stored the energy somehow. Ocean heat measurements have generally confirmed this, with some investigation still on margins of error.
That's a pretty long winded and well documented way of stating I agree with your points. I still hold to my context being just fine though in observing that climate models systematically overestimated temperatures since 1998. I still stand that it very much IS a relevant and important observation and criticism. Here's why with some more references to the IPCC's assessment of models linked earlier. As mentioned before, the heart of the warming problem is the global energy balance, and how much extra energy CO2 and other processes are helping to add to our planet each year. It's generally referenced as the Top Of Atmosphere energy balance(TOA), and in the long term, it's virtually the only variable that really truly matters to what is happening to our planet. Ultimately more energy in in the long run will raise temperatures, similarly more energy out will lower them. How that energy gets distributed between air and oceans and globally is a secondary consideration. I state all this because when the climate models are being prepared, one of the last steps is 'tuning' parameters in them so that they are accurate. Here's a quote from the IPCC on that:
Model tuning aims to match observed climate system behaviour and so is connected to judgements as to what constitutes a skilful representation of the Earth’s climate. For instance, maintaining the global mean top of the atmosphere (TOA) energy balance in a simulation of pre-industrial climate is essential to prevent the climate system from drifting to an unrealistic state. The models used in this report almost universally contain adjustments to parameters in their treatment of clouds to fulfil this important constraint of the climate system (Watanabe et al., 2010; Donner et al., 2011; Gent et al., 2011; Golaz et al., 2011; Martin et al., 2011; Hazeleger et al., 2012; Mauritsen et al., 2012; Hourdin et al., 2013).
So, this leads me to one accusation, that hindcasting skill within the models is biased on the most important element(TOA Energy balance), by design. That's not declaring the models bad science, instead it is just observing that the climate models are merely hindcasting with the benefit of having the energy balance corrected by hand. Modelling the distribution of that energy between geography and air/ocean boundaries is still all good science and being done. The thing is, energy balance going forward matters a lot as we should expect to make predictions of increasing CO2 driving the energy balance up and predicting that is much more important while regrettably our hindcasting fails to test this.
The IPCC also further notes:
Model tuning directly influences the evaluation of climate models, as the quantities that are tuned cannot be used in model evaluation. Quantities closely related to those tuned will provide only weak tests of model performance.
Notably, clouds being a near universally tuned parameter in order to maintain reasonable TOA balance sets us up with models with built in limitations. Cloud behaviour can't really be tested because it is used to tune the energy balance. Energy balance can't really be tested because we hand tune it to would we 'know' it should be. The observed record tells us that energy imbalance since 2000 has no trend, it's been a steady increase neither gaining or losing rate(per IPCC). The observed record tells us that CO2 since 1900 has been rising very noticeably. With rising CO2 we should expect the energy imbalance to grow as well, but it isn't. That's about the time where I want to see climate models that can test if clouds are part of the equation mitigating the energy imbalance the CO2 should be causing. Regrettably as noted, clouds and TOA energy imbalance are two things that the climate models are tuned for or with...
If you don't get the drift, I lack confidence in the computer models overall veracity given the important role of clouds and the TOA energy balance. Something like the models systematically missing a trend like that since 1998 kind of confirms that. I'm a comp sci guy by trade, so computer models are something I get and understand. Modelling complex systems requires compromises and estimates, but I really have serious troubles swallowing the value in tuning for TOA when that is driving force for the entire system. Getting the macro long term temperature trends in the right ballpark over a few centuries is kind of a gimme if you don't have to predict the TOA changes accurately and can just tune it till your right.