We not only need to reduce CO2 emissions, (Already an expensive problem) but somehow, (added to that) we have to get rid of a large amount already in the atmosphere.

Opinion | Saving the world with carbon dioxide removal

Peter Wadhams is professor of ocean physics in the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge, U.K. CAMBRIDGE - Limiting global warming to 2 degrees Celsius above preindustrial levels, as the countries of the world committed themselves to do under the Paris climate accord, is impossible without removing carbon dioxide from the atmosphere.

From article, (If we want to survive climate change, we must double down in research manpower and dollars to find and improve technology to remove carbon dioxide — or at least reduce its effects on the climate. We now emit 41 billion tons of carbon dioxide per year. The current level of carbon dioxide in the atmosphere is already high enough to bring about a warming of more than 2 degrees after it has worked its way through the climate system, so if we want to save the Paris accord, we must either reduce our emissions to zero, which is not yet possible, or combine a significant emissions reduction with the physical removal of about 20 billion tons of carbon dioxide from the atmosphere per year indefinitely.

Effective and impactful carbon dioxide removal operations will need to be in place by around 2020. To keep global temperature rise within acceptable limits, we’ll need to remove half the current human emissions, which means extracting about 20 billion tons of carbon dioxide each year, indefinitely. If we can manage this, we can save our society and our children’s futures. After all, if carbon dioxide is the chief cause of climate change, its removal would be our salvation.

Currently, the best way to save our future is to remove carbon dioxide through direct air capture, a process that involves pumping air through a system that removes carbon dioxide and either liquefies it and stores it or chemically turns it into a substance either inert or useful. Enterprising researchers have already developed systems that work by passing air through anion-exchange resins that contain hydroxide or carbonate groups that when dry, absorb carbon dioxide and release it when moist. The extracted carbon dioxide can then be compressed, stored in liquid form and deposited underground using carbon capture and storage technologies.

The challenge here is to bring the cost of this process to below $40 per ton of carbon removed, since this is the estimated cost to the planet of our emissions. At the moment, most methods cost more than $100 per ton, but there are dramatic developments which promise great improvement. Three companies have opened pilot plants — Global Thermostat (United States), Carbon Engineering (Canada) and Climeworks (Switzerland).)