Science

This is the removal of carbon dioxide from the atmosphere.

Now, to be sure, this is likely to be an extremely challenging enterprise, but it stands at the edge of feasibility - it's hardly likely but it is, to my mind, feasible.

It is often discussed in the literature in terms of "DAC" (Direct Air Capture) but I think there is a better approach, which is removal of carbon dioxide from seawater, since the concentration of carbon dioxide, bicarbonate, and carbonate is higher than in air volumetrically. Nevertheless the thermodynamic penalty is enormous, but perhaps can be addressed by process intensification using high temperature nuclear reactors. I drive this point frequently with my son who is in a Ph.D. nuclear engineering program.

This approach would address the entropy of mixing, which must be overcome to concentrate carbon dioxide, and involves the recovery of only some of the energy of putting the CO₂ there in the first place.

This leaves the problem of what to do with the carbon dioxide, which to my mind, must be reduced to carbon or carbon compounds, thus requiring reproducing all of the enthalpy of oxidation of the dangerous fossil fuels that put the CO₂ there in the first place.

In other words, future generations will be required to produce not only all of the energy they need for their lives, but all of the energy produced by previous generations, our generation included, the one history will not forgive.

This is only accessible with very high energy efficiency - exergy recovery at an unprecedented scale - and very matter with an enormous energy to mass ratio, only available in the form of the actinides thorium and uranium, and possibly, but certainly not certain, tritium and deuterium in fusion settings.

Public ignorance driven by advertising and wishful thinking resulting from that advertising makes this an enormous challenge, unprecedented in human history. I don't think we're even remotely close to facing these realities.

My opinion of all other "geoengineering" schemes is that they are all garbage and won't work and much like "solar and wind will save us" trash thinking will only serve to make things worse.

Thanks for asking.