1 foot ocean rise per century.
Threat?
Unimitigated, the forecasts are around 3-7 feet sea level rise this century.
Both of these massively increase the probability of non linear disasters including the release of methane from permafrost and ocean floors, or the disruption of the Gulf stream which would disrupt global agriculture even worse than a 5 degree temperature rise.
Among the many problems, you can expect heat to be so hot that 1 billion people will be living in a place where it's not physically possible to live (humidity doesn't allow the body to cool down): https://eu.usatoday.com/story/news/world/2020/05/04/world-he.... It won't exactly be all roses to the other billions too
It's absolutely a bigger threat than the terrorism that everybody was so eager to throw away their freedom for 19 years ago.
Got better, actually.
As you said, autocracies are efficient for hard problems, and we're going to face the hardest very soon