Negative CO2 emissions
If GHG emissions can’t be curbed fast enough, technologies to mitigate past GHG emissions are being developed.
Technologies for removing carbon dioxide from the atmosphere have received funding. They can use the same technology to remove CO2 from Navy submarines’ air. They can absorb CO2 from the atmosphere with reforestation of deserts with limited watering. They can grow plants, burn them to produce enough energy for capturing CO2 before injecting it in the ground.
Agriculture technologies can be included in this category, as space and energy for food will be part of the equation, especially to feed over 9 billion people by 2100. New approaches are being developed. They range from vertical agriculture to GMOs.
As a last resort, geoengineering could shield the earth from solar energy in order to cool it, with sulfur dioxide clouds, with gigantic mirrors in the stratosphere, with artificial vapor cloud creation. These technologies are untested and may backfire with unexpected consequences. As temperatures keep climbing, some bet that geoengineering tech will be required one day.