I agree it seems a silly target, people doing the right thing, but I think their point was we cannot continue business as usual and just hope for the best.
https://www.nme.com/news/music/plan-ongoing-escalation-insid...
If a demonstration is actively blocking people from commuting then it's just harming innocent civilians and only hurting the cause. There are better ways to create change then causing chaos in the lives of people who can't do anything about it.
The thing about this day and age, is that it is generally different than it was yesterday.
The Extinction Rebellion protests have so far been some of the most successful in recent memory, they had politicians scrambling to be the first to declare a 'climate emergency'. Whether the talk converts to any action is another thing, but they have been very successful in raising the political visibility of the issue.
If I see a fire in the house I am in, it might be in the grate, or it might be on the sofa. If I declare some sort of 'fire emergency', it can help to point out to other humans which of the two situations I think I am encountering and how they might therefore choose to react.
I hope this helps.
For example, Trump declared immigration a national emergency in an attempt to use funds to build the wall that he would not have otherwise been able to do so. See the second paragraph of https://en.m.wikipedia.org/wiki/National_Emergency_Concernin...
Now, while there is no protest without any use of force (whether force of gravity by peacefully taking over an area, requiring force to be removed, or "force of language"), we generally categorise protest as peaceful if force is only used in defiance (you have to use the force to remove me).
Peaceful protest does not equate to inconvenient to everybody (actually, they are usually designed to be inconvenient to get their message across). Civilians are not "innocent" in the sense that they have elected the government a protest is aimed at. How much sympathy protesters will get is a topic of discussion for themselves, and I am sure they carefully weigh that before staging a protest.
If you can't distance your inconvenience from whether the protest has merits, you probably don't intrinsically trust the democratic process ("I know better what they need").
Seems like "raising awareness" is a convenient blanket excuse for people to do whatever the fuck they want, and blame everyone else if the actions breed resentment that's counterproductive to the original goal.
I've also already mentioned it should be a calculated risk on protesters' side: aim to win more people than you lose those who can't empathise with protesters.
I am not saying that all protests succeed, or that I agree with all of their goals, but I stand by their right to inconvenience me in order to get heard (and yes, there were cases were my personal circumstances would have made me furious at that moment, but that would not affect my general opinion of the approach).
Regarding what it actually accomplishes, here[1] is an older rundown (from April) of their main requests and the results so far.
[0]: https://www.youtube.com/watch?v=y6xT62MZrRM
[1]: https://www.theguardian.com/environment/2019/apr/25/extincti...
Not to mention, people only agree when they're not the ones in the commute.
Here's an article on it: https://www.salon.com/2015/07/10/this_is_what_its_going_to_l...
Some predictions are even more extreme: https://phys.org/news/2015-09-fossil-fuel-meter-sea.html
It's probably not the most likely outcome, but it's also definitely not "fear mongering bs", it's part of what science is discussing as possibilities.
I.e. about the "extra 20ft of risen sea"
The recent studies I've explored predict around 50-130cm by 2100. However, I have seen discussions of ~20ft by 2200 and 26ft by 2300 (https://www.theatlantic.com/science/archive/2019/01/sea-leve...), alongside more alarming figures (https://www.annualreviews.org/doi/10.1146/annurev-environ-10...).
You might be interested to read The Myth of the 1970s Global Cooling Scientific Consensus: http://nora.nerc.ac.uk/id/eprint/11584/1/2008bams2370%252E1....
Excerpt: "There was no scientific consensus in the 1970s that the Earth was headed into an imminent ice age. Indeed, the possibility of anthropogenic warming dominated the peer-reviewed literature even then."