To clarify, the method is not sufficient to detect a temperature variation within 100 years - current methods aren’t that specific with dates.

One could read your comment as “we haven’t detected temperature variation in past data that’s similar to the recent rise”, but what you are trying to say (and what the link says) is that we’ve seen the variation before, we just can’t tell exactly how quickly it happened.

No, our methods simply can't detect narrow spikes in past data:

"no temperature variability is preserved in our reconstruction at cycles shorter than 300 years"

This means if there was temperature variation in past data current methods couldn't detect it, so the absence of spikes in the data is not proof of absence. In other words, if global warming was reversed and 200 years from now temperatures went back to pre-industrial levels it would be undetectable 10000 years into the future with our current methods.

Yes, but atmospheric co2 sticks around for 300-1000 years and the resulting temperature spike should therefore definitely be detecteable. They might not be able to pin point the exact period of 100 years we started to industrialise but it will definitely be able to see the change and determine that this took place over a timeline 100-1000 times shorter than previous similar changes.

Furthermore, there will be massive cooroborating evidence in the form of fossile records showing a mass extinction event and ice core samples (assuming we will still have icesheets) showing the accompanying rise in co2 levels as ice layers are deposited on a yearly basis.

Well that certainly gives a different spin to the various competing claims regarding global warming…