Humans have caused 1.5 °C of long-term global warming according to new estimates

That seems… very low?

Yes, seems that way, but the impact will be huge.

https://interactive.carbonbrief.org/impacts-climate-change-o...

See also:

https://www.un.org/en/climatechange/science/climate-issues/d...

It might sound low, but consider that this number is a distillation of many changes into one proxy which roughly covers a variety of different effects that aren’t strictly related to just temperature.

For example, consider ocean acidification.

Also consider the number of tipping points and positive feedback loops that exist. How close are we to those?

Depends on context. for example 1C for all water on earth is still on 1C+ but one would need a lot of energy for that.

from open ai: The power required to raise the temperature of all the Earth's water by 1°C in one second would be 5.57 × 10¹⁸ megawatts.

- 70 to 90% of coral reefs dying, devastation of maritime ecosystems

- potential collapse of maritime currents that lead to relatively mild climates in Britain

- triggering of multiple irreversible climate tipping points (arctic ice sheet)

- more common and much more devastating extreme weather events (warmer air can carry more water)

- the aforementioned weather results in infrastructure damage and lack of food within big parts of the world. Waves of migration

- median sea level rise of more than a meter means extremes will be much higher, a big part of the human population lives next to the sea

And much more — this was the absolute minimum and we surpassed it faster than expected.

1.5 degrees celsius is 10% of the global average temperature. That is, to put it mildly, a shit ton of a difference

If doesn't make sense to take the percentage of a quantity in units with an arbitrary reference point. In Kelvin it would be about 0.5%.

Celsius is not an absolute scale. You need to use Kelvin for that meaning that a 1.5C increase is close to a 0.5% increase in global average temperature.