The IPCC used to consider an increase of 3.5°C as a catastrophic change, but they have moved to goalpost to 2°C and targeted policy for 1.5°C. Keep in mind that is measured from pre-industrial times. The average temperature is already 1.1°C above pre-industrial levels.
So, we’re basing policy on trying to hold temperatures to a increase of 0.4°C between now and 2100, just over a third of the change over the last 100 years.
We can’t even measure average global temperature within 1°C