The fear is that, with the Tonga eruption, this larger than normal hole might do extra damage to the vast store of ice on Antactica.
Why is this concerning?
Well, given the Antarctic and the Greenland icesheet has enough ice to raise sea levels by 65m worldwide. This means a 5% melt in Antarctica would raise sea levels by several meters (even without any melting of Greenland at all).
This quantity of sea level rise, would threaten cities such as Shanghai and London, to large parts of Florida and Bangladesh to total nations that would be wiped out, such as Maldives.
This means that while it may well take a century and increased carbon emissions for all of the ice at the poles to melt, it could threaten human populations long before this occurs.
Around 410 million people on earth live within just 2m of the height of the sea. This is roughly 5% of human population. Currently, there are issues with just 2% immigration into the UK. A sea level rise of 2m would likely trigger an order of magnitude more to move here, Western Europe, USA and other countries. We are all going to be hit hard, but some far harder than others.
