Geologist Peter Ward fears too little CO2 in a future Earth. Below 100 ppm photosynthesis ceases. Plants and animals all die. Only alternative energy organism survive.
Earth likely began with 50% CO2 (like Mars and Venus). By the time life emerged from thebsea is was only a couple percent; just 0.04% (400 ppm) now. During ice age advances its been as low as 180 ppm.
As the Earth cools off, there will be less plate tectonics and volconism to replenish CO2. Ward predicts a half billion years or less for the CO2 apocalypse. If there still is sentient life then, there is an easy remedy. 98% of near surface carbon is in limestone. Just burn enough limestone (as we currently do for cement manufacture).
An apocalypse half a billion years away? In what context does the word "fears" make sense on that kind of scale?
If we're still around then, and still dependent on this planet, and haven't transformed it into an entirely different ecosystem (all these ifs seem incredibly unlikely), then as you say there are easy fixes that even we at our current technological level could pull off.
Earth likely began with 50% CO2 (like Mars and Venus). By the time life emerged from thebsea is was only a couple percent; just 0.04% (400 ppm) now. During ice age advances its been as low as 180 ppm.
As the Earth cools off, there will be less plate tectonics and volconism to replenish CO2. Ward predicts a half billion years or less for the CO2 apocalypse. If there still is sentient life then, there is an easy remedy. 98% of near surface carbon is in limestone. Just burn enough limestone (as we currently do for cement manufacture).