"However, complete melting of Thwaites Glacier, which would increase global sea levels by 65 cm or 2 feet, is unlikely to occur for many centuries."
How much hotter overall on the planet would the temperature have to rise for that polar Glacier to become totally melted? I found these temperature averages for Antartica:
"At the South Pole, 2,800 meters (9,200 feet) above sea level, the average annual temperature is -49 °C (-56 °F), ranging from about -28 °C (-18 °F) in January to about -59.5 °C (-74.5 °F) in July. The lowest recorded temperature is -83 °C (-117 °F), while the highest is -12 °C (10 °F)." [2]
So, basically, we'd have to get an average temperature increase on the planet of (ballpark figure) 40 °F for the Glacier to start melting overall. I say this, because I am assuming that the current area of the glacier that melts is where it meets the ocean.
1. https://en.wikipedia.org/wiki/Thwaites_Ice_Shelf 2. https://www.climatestotravel.com/climate/antarctica