Fun with FaIR: How many years of temporarily reduced emissions (such as a pandemic!) does it take to make a dent in the 2100 temperature projection?

I played with FaIR $($Finite Amplitude Impulse Response simple climate model$)$ to look at the impact of the temporary reduction in emissions on global mean surface temperature change. The projected decrease in greenhouse gas emissions as a result of the pandemic vary a lot, but I just wanted to play with this model and have a sense of orders of magnitude.

The total temperature change from increased CO2 is a function of cumulative emissions so it is no surprise that a temporary reduction in emissions does not change the temperature at 2100 that much. But just how long does it take to make a dent?

I made a few simple assumptions to get an upper bound on temperature change: we follow RCP4.5 and years of “reduced” emissions actually have zero$($!$)$ emissions.

For 2 years of zero emissions, we barely get any change in temperature at 2100.

For 10 years of zero emissions, we get order 0.1 degrees less warming by 2100.

Finally, for 30 years of zero emissions, we get order 0.5 degrees less warming by 2100.

Check out the $($barely modified tutorial$)$ code here.