The idea in the book was this was a new event that never occurred previously that finally did and was able to demonstrate that climate change is doing some new and not survivable.
In the book, people galvanized around it kind of like 9/11 as it was clearly climate change, as opposed to other things that already existed and may or may not be due to climate change (more hurricanes, etc).
Be careful what you wish for. 9/11 galvanized Americans to start two disastrous wars. The effect of a mass fatality event like in MFTF could easily be a bunch of pointless, ineffective wars. There's precedent for that, but not for anything like a Ministry for the Future
In the book, people galvanized around it kind of like 9/11 as it was clearly climate change, as opposed to other things that already existed and may or may not be due to climate change (more hurricanes, etc).