I think the far bigger problem will be that it won't really be that bad for the next 50 years, leading to complacency, and we will hit the point of no return before we really feel much impact in the richer western countries.
The 18 month stat is a mashup of two totally different deadlines. First, that we need strong emissions commitments by 2020, which is not a meteorological deadline but a political one: UN meeting schedules and the Paris Agreement call for strengthened emissions plans by 2020, so failing to act by then implies an overall lack of political will. Second, the IPCC report that CO2 emissions need to peak by 2020 to keep warming below 1.5 C by 2100. That's important and hard to reach, but "peak" is not "become net negative" and >1.5C is not "doomed".
The 12 year stat is basically backwards - confusing an emissions deadline with a temperature peak. The IPCC finding is that we'll reach 1.5 C of total post-1975 warming between 2030 and 2050, and that major emissions cuts by 2030 (and net-zero by 2050) could limit warming to 1.5C. The worst case described was 3C by 2100, not 2030, and harms arriving some time after their "locked in" warming thresholds.
None of that means it's not a serious problem, or that rapid action isn't needed, but I'm really disturbed to see people predicting death and doom for what are actually emissions deadlines. It seems like an attempt to trick people into acting fast, but action that fast isn't actually possible. I think that instead we're going to get to the 2020s and be hearing "you said the world would end but things are still basically ok, you're full of shit, clearly we don't need to keep taking action".
This isn't necessarily validated by hard scientific evidence, but I have a suspicion that climate change is exacerbating conflict in the middle east. For one, heat is a known catalyst for violence. But also, as desertification takes effect, resources become constrained, creating conflict.
The US has a refugee crisis stemming directly from the loss of arable land in Central America, and Europe is suffering from one as a result of the a massive drought and the Arab Spring hitting Syria.
Effects of emissions take about 20-30 years to be seen, so today’s emissions are already locked in to be felt mid-century. That should help put the 1 degree C rise you mentioned in proper context.
So, yes, things are that gloomy. We need immediate, global efforts in a war-like sense to change our entire energy sector if we are to avert the worst of it, and of course we’re only headed faster and more headstrong in the opposite direction. It’s not incorrect to say that we’re most likely completely fucked, and that Gen Z will be the last generation to experience a peaceful planet.
We have hit the point of no return. The only options available to us right now are how to minimize the inevitable effects.