Since I have a few free moments, I thought I would briefly highlight a paper by Jenkins et al. on [t]he Multi-Decadal Response to Net Zero CO2 Emissions and Implications for Emissions Policy. Recent IPCC reports have highlighted that limiting human-caused warming will require getting human emissions to (net) zero. What this paper suggests is that it might be better to aim for approximately net zero.
The analysis in the paper suggests that positive emissions of 2.2GtCO2/yr might be consistent with halting anthropgenic warming on multi-decadal timescales. The 95% range, though, is from -7.3GtCO2/yr to +6.2GtCO2/yr, so it could be higher, or it could require net-negative emissions. As far as I can see, this is broadly consistent with earlier work on the zero emission commitment, which suggested that the best estimate was that zero emissions would stabilise human-caused warming, but that it could also lead to some continued warming, or some cooling.
Personally, I quite like the suggestion of thinking in terms of approximate net zero. If we can reduce human emissions by ~90% (which is what would be required to get to ~2.2GtCO2/yr) then even if it doesn’t quite stabilise human-caused warming, it should significantly reduce the rate of warming. It woiuld give us some time to work out if emissions need to be reduced further, and if we would need to implement significant amounts of negative emissions.
Of course, it’s still not going to be easy to reduce emissions by ~90%, which is another reason why I quite like the idea of thinking in terms of approximate net zero; let’s try and get close before worrying about whether or not it has to be exactly zero, or negative.