[spencerchubb]

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

[mr_mitm]

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%.

[wtcactus]

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.