It seems to me that respected climate scientists are split into two camps. Am I wrong?
I think of them as Old School and New School.
The Old School says that because CO₂ (Carbon Dioxide) does not react in our atmosphere with any other gases, all the CO₂ added by burning fossil fuels stays up there nearly forever. This means that there is a fixed budget of how much CO₂ can be produced before the blanket of CO₂ gets thick enough to raise temperature above the Paris Agreement limits. The speed at which CO₂ is added doesn’t matter, only the total added. Hence the fixed Carbon Budget.
The New School says that if that was the end of the story a fixed budget would be true, but there is Natural Sequestration that needs to be added, or rather subtracted, from the equation.
To use the well-worn bathtub analogy. The Old School says that there is only a fixed amount of CO₂ that can be added before the bathtub overflows. While the New School says that the bathtub has a drain, and the bath plug isn’t blocking it. The drain is only removing half the amount of CO₂ being added by the taps, but this has a dramatic effect on how quickly the bathtub fills. It also means that if the CO₂ taps are turned off then the bathtub will start emptying and drop to the old level.
This is a simplification since the drain doesn’t quite work like that and will not work as efficiently in future. The Natural Sequestration drain is roughly half CO₂ removal being by ocean absorption, the other half by plants. Both of these mechanisms will probably become less efficient, but not stop completely.
This split has resulted in both versions being included in the IPCC Assessment Reports. It also seems to have resulted in Climate Change models some of which include Natural Sequestration, but some don’t. Since Natural Sequestration amounts to an amount just over half of annual CO₂ emissions, this is a major omission.
