Greenhouse gas regulation is like groundwater management

Or I guess it should be the converse of groundwater management. With groundwater, you can withdraw a certain amount that corresponds to the annual influx, without lowering the water table. Or you can overdraft the groundwater by taking out more than comes in, without stressing the system too much, so long as your overdraft doesn't lower the water table below a level that interferes with your management goals. A typical goal would be to not lower the table any more than the depth of the shallowest well drawing from that table. A modern environmental goal would be to not dry up any critical springs or streams dependent on the water table.

Groundwater overdraft corresponds to the amount of anthropogenic emissions at any one time that exceeds the absorption capability of the environment. The groundwater buffer between a safe and unsafe overdraft corresponds to the increased ppm concentration of greenhouse gases that lies below a level that creates a "dangerous anthropogenic interference in climate," whatever that is.

Don't know if this is helpful for anyone else, but it helps me think about it. And we here in the American West have a history of bad groundwater management regimes, so I think I see some parallels.