It would only cost about as much as the futile wars in Iraq and Afghanistan to implement Be/CCS solutions at scale to reduce CO2 to pre-industrial levels (280 ppm). The key is sequestration because without that, like the recent virtue-signaling in Africa, growing a bunch of trees in poor soil is pointless: it doesn't stop desertification, increased risk of forest fires and dying/burning trees above ground doesn't capture any net carbon.