A very significant challenge to meet this requirement in the overall attempt to rescue humanity, is that we do not currently have a process that can easily (or even with difficulty) scale up to the size needed to remove CO₂ from the atmosphere at a high rate of removal – something on the order of 40 Gt per year was the most recent rate at which CO₂ was added, so we might presume to take it back out at the same rate. There is currently no known mechanical technology available at this scale of removal of CO₂. There are several prototypes of scrubbers that bring air through large fans. The cost to produce CO₂ from the atmosphere, so that it can be sequestered, ranges from about $10 to $50/ton. This cost does not include the capital cost to build the facility. One Canadian company has an operational prototype that produces about 1 ton CO₂ per day and cost $9million to build. If this is scaled up to remove CO₂ sufficient bring the atmospheric concentration down to 280ppm, the annual operating cost for a 50-100 year project would be about $9 trillion per year, not counting the cost of construction. With a lifetime span of about 20 years, the plants would need to be replaced twice in the 50 year project. Amortising these costs would bring the annual total up to about $4.5 quadrillion per year.

Given that the total GDP for the planet is only about $120 trillion per year, this technology simply cannot do the job. To bring it into line with reality, the efficiency of production and construction needs to be multiplied by a factor of over 1,000 times to bring it into the range of $4.5trillions per year.

Is this possible? Given the scale of the problem, it is not likely to be smart to rely entirely on that technology being developed in time. While we develop Plan B, let’s assume the technological scrubbers can be brought to scale and efficiency in time as Plan A.

The other options for Plan B are almost all based on some form of geo-engineering. Spraying high altitude sulphur or other aerosols such as calcite crystals, putting space mirrors to reflect the sun away from the planet, adding chaff, or several other ideas would not change the atmospheric concentration of CO₂, but might bring the temperature down. These are very temporary and expensive alternatives.

Another option is to copy the natural relationship with dust in the ocean. As described earlier, blowing dust falls in the ocean. The dust contains minerals that limit the productivity of phytoplankton. More dust produces more phytoplankton productivity. To grow and reproduce, phytoplankton require carbon, which they take from the ocean water. As the carbon in the ocean declines and is sequestered in the phytoplankton, CO₂ from the atmosphere dissolves into the ocean. In addition, during growth phytoplankton produce dimethyl sulfide (DMS), the primary source of direct and cloud-related indirect cooling effects on climate (Grandley et, 2015). Experiments to test the effectiveness of removing carbon from the ocean to indirectly reduce atmospheric concentrations of CO₂ have not been of large enough scale to detect much change in atmospheric CO₂. However, if iron-rich dust from a potential range of sources were added to the normally relatively barren areas of the ocean, it is definitely possible to raise the productivity of phytoplankton. In one experiment (Wingenter, et al, 2007) ion rich dust was added to two patches of Southern Ocean about 100 square miles each. From this experiment the researchers concluded that fertilizing 2% of the Southern Ocean would result in a 20⁰C drop in regional temperatures. They further estimated that this would entail 30 ships to distribute 22 kilotons of iron sulfate at an annual cost of between $10million and $100million. If this approach were scaled up to include a portion of the entire Pacific and Atlantic oceans, the cost increase might be on the order of 10 times – 300 ships with annual expenditures of between $100million and $1,000million. Tuning this experiment to manage the climate as well as terminating the ocean fertilization theoretically will be relatively quick because the phytoplankton life cycle is roughly 6 days. The rapidity with which the excess iron sulfate would dissipate is unknown but is likely also to be relatively rapid as the blooms use up the diminishing resource.

To consider the consequences using only technology, let us assume that during the emissions reduction project, a full-fledged technical program to develop a cost effective carbon capture and sequestration is successful. We could consider that as a first approximation we might be able to assume the cost will be similar in scope to the cost of producing energy. The two estimates we found were between an upper estimate of $9.545 trillion per year and a lower estimate of $4.888 trillion per year.

At 40 Gt per year removal rate from the atmosphere with a zero emissions regime as the context, the time frame for the project will be from 2066 to 2131 assuming the project eases into and out of full scale operations. The project is about 65 years of scrubbing CO₂ out of the atmosphere (15 years longer than the energy transition project). The maximum total 65 year cost of the project is estimated at $620.4 trillion and the minimum is $317.2 trillion. The combined cost is about $1,098 trillion for all renewables and about $562 trillion for a mix of nuclear and renewables.

If a technical solution to carbon capture and sequestration is not found, then an oceanic seeding project becomes an important potential plan. It is much less expensive in direct cost than the likely technical solution, but without preliminary experimentation, the effects on oceanic ecosystems remain speculative.

A more modern economic model would argue that instead of discounting the future to zero, it is more logical to equate the future value to current value. In this model, sustainability and ensuring that the future value is maintained is part of the economic logic. In this case, the “project” that we have embarked on – adding CO₂ and methane to the atmosphere has a life span of at least 2,500 years or more. So in our case, as opposed to normal business thinking, the future is a time beyond the year 4500AD. Using this as our business model, the total value of the project is at least $1.2 quadrillion (the value of all financial derivatives).

But it is not all about money. There is a human cost as well. Let us suppose that the project to reduce atmospheric CO₂ to 280ppm is successful. The sea level will inevitably rise about 8m. According to the US Geological Survey estimates the number of people who will become refugees because of being flooded will be between 500,000 and almost a billion people (Chart #3) – and that is only as a result of sea level rise. There are many other inevitable and very negative changes that will occur as the temperature increases.