Global Warming and Cooling After CO2 Shutoff at +1.5°C
I have done further analytical modeling of global warming, using the same general method described earlier.
The question addressed now is: what is the trend of temperature change after an abrupt shutoff of all CO2 emissions just as the net temperature rise (relative to year 1910) reaches +1.5°C, given the lifetime of CO2 in the atmosphere?
For this problem, it is assumed that when the temperature rise (relative to 1910) reaches ~+1.5°C, that:
– all greenhouse gas emissions cease;
– pollution grit (which scatters light) falls out of the atmosphere “instantly” (a few weeks);
– CO2 (greenhouse gas) concentration decays exponentially after emissions shutoff;
– for CO2 lifetimes [e^-1] in years: 20, 50, 100, 238.436, 500, 1,000, 10,000, 100,000;
– temperature sensitivities of cloud cover, ice cover and albedo are as in the previous model;
– all other fixed physical parameters are as in the previous model,
(https://manuelgarciajr.com/2020/06/13/living-with-global-warming/).
In general, for the 8 cases calculated, the temperature increases at a diminishing rate after the emissions shutoff, reaches a peak, then trends downward.
The longer the lifetime of carbon dioxide in the atmosphere, the later and higher is the temperature peak, and the longer it takes to cool back down to the baseline temperature of 1910, which is 1.5°C below the starting temperature for this problem.
The 4 figures below show the calculated results.
Figure 1: °C change vs. years after shutoff, for lifetimes: 20, 50, 100, 238.436 years.
Figure 2: °C change vs. years after shutoff, for lifetimes: 20, 50, 100, 238.436, 500, 1,000 years.
Figure 3: °C change vs. years after shutoff, for lifetimes: 238.436, 500, 1,000, 10,000 years.
Figure 4: °C change vs. years after shutoff, for lifetimes: 1,000, 10,000, 100,000 years.
It is evident from the figures that if the lifetime of carbon dioxide in the atmosphere is greater than 500 years, that a temperature overshoot above +2.0°C (relative to 1910) will occur before cooling begins.
…click on the above link to read the rest of the article…
