Scientists want to spray sulphur dioxide into the atmosphere to refreeze the poles

A fleet of roughly 125 tankers could return subpolar regions close to pre-industrial temperatures.
Sade Agard
Plane flying over the poles.

Paul Campbell/iStock 

Scientists presented a controversial plan whereby high-flying jets similar to a modified American KC-135R could spray microscopic aerosol particles into the atmosphere to refreeze the North and South Poles. The recently published research in IOP's Environmental Research Communications suggests that the method would be feasible and fairly cheap.

The plan, which falls under a controversial climate intervention technology called Stratospheric aerosol injection (SAI), would target only subpolar regions- instead of having a global intervention that most other SIA operations assume, highlights the paper.

The SAIL-43K: A step up from 'hand-me-down' military air-to-air refueling tankers

REPLACED
The SAIL-43K- an efficient candidate for the subpolar mission

The researchers argue that 'hand-me-down' (reused) military air-to-air refueling tankers such as the aged KC-135 and the A330 MMRT don't have enough payload at the required altitudes- even when modified. They, therefore, submit the SAIL-43K as an efficient candidate for the subpolar mission.

A fleet of 125 of these SAIL-43K tankers would release a cloud of microscopic sulfur dioxide particles, which at an altitude of 43,000 feet (13 kilometers) and latitude of 60 degrees north and south- could loft a payload sufficient to cool the regions by two degrees per year. Areas such as Anchorage, southern Alaska, and the southern tip of Patagonia- could return close to their pre-industrial average temperatures.

Upon slowly drifting towards the poles by ferrying on high-altitude winds, the particles would slightly shade the Earth's surface beneath.

An operation would be equivalent to more than two days of global commercial air traffic

Still, the paper highlights that such an operation would be equivalent to more than two days of global commercial air traffic in 2021, or about two-thirds of the annual flights departing New York's Kennedy Airport.

The SIA operation would tap into the healthy number of pre-existing commercial airfields in the Northern Hemisphere that could serve as operational bases for a polar SAI operation. Anchorage, for example, has three runways longer than 10,600 feet, and whilst located at 61.2°N latitude—this would be close enough for the purpose.

For the southern hemisphere, it's a little more complicated. 60 degrees of the south pole touches nowhere on land and is inhabitable. The closest significant airfields are in Chile and Argentina at the southern tip of Patagonia. As sub-optimal bases here may be relative to the 60°S target, the researchers reveal they will have to serve.

Additionally, the paper highlights that the ground infrastructure for any pre-existing base would need to be greatly enhanced to accommodate the program.

Costs are less than one-third of alternative climate responses aiming to cool to the same 2°C extent

According to the paper, the costs of the subpolar SIA program are estimated at 11 billion dollars annually. This is less than one-third the cost of cooling the entire planet by the same 2°C extent proposed by other climate responses such as mitigation, adaptation, or carbon capture and sequestration.

Nevertheless, to compare the newly proposed SIA operation with the alternatives mentioned above would be like comparing apples and oranges, admits the researchers.

A subpolar mission using highly controversial technology

Whilst subpolar in nature, using the airspace of no more than a dozen countries, it still stands that the program is controversial.

The governance and legitimacy challenges that would confront such a program include not knowing the unintended consequences of releasing sulfur particles into the atmosphere, such as reducing crop yields.

A short while ago, a similar SIA plan in Sweden by a Harvard research project had to be abandoned due to environmental protests. In this case, scientists proposed using balloons to release the particle and further consolidate the need for international agreement.

Still, the researchers behind the newly proposed program argue that their SAI program would entail deployment directly overhead of far less than 1% of the world's population and nearly none of its agriculture. Given its apparent feasibility and low cost, this scenario deserves further attention.

Regardless of the outcome, the current study still provides a boost in understanding the costs, benefits, and risks of such climate intervention measures at latitudes of thousands of feet. Who knows, perhaps such tools could prove helpful in saving the cryosphere near the poles and delaying global sea level rise.

After all, the poles are warming several times faster than the global average. It was only last year that we saw record-breaking heatwaves reported in both the Arctic and the Antarctic.

Study abstract:

Stratospheric aerosol injection (SAI) is a prospective climate intervention technology that would seek to abate climate change by deflecting back into space a small fraction of the incoming solar radiation. While most consideration given to SAI assumes a global intervention, this paper considers an alternative scenario whereby SAI might be deployed only in the subpolar regions. Subpolar deployment would quickly envelope the poles as well and could arrest or reverse ice and permafrost melt at high latitudes. This would yield global benefit by retarding sea level rise. Given that effective SAI deployment could be achieved at much lower altitudes in these regions than would be required in the tropics, it is commonly assumed that subpolar deployment would present fewer aeronautical challenges. An SAI deployment intended to reduce average surface temperatures in both the Arctic and Antarctic regions by 2 °C is deemed here to be feasible at relatively low cost with conventional technologies. However, we do not find that such a deployment could be undertaken with a small fleet of pre-existing aircraft, nor that relegating such a program to these sparsely populated regions would obviate the myriad governance challenges that would confront any such deployment. Nevertheless, given its feasibility and potential global benefit, the prospect of subpolar-focused SAI warrants greater attention.

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