The “Relatively Low Cost” plan would cool the Earth’s poles by 2 ° C

New research suggests that 2 ° C (3.6 ° F) pole cooling and Arctic and Antarctic refreezing are “feasible at relatively low cost with conventional technologies,” using stratospheric aerosol injection. (SAI) of heat reflective particles concentrated on the poles. The side effects may be unpleasant and the policy nearly impossible, but the plan offers a way to slow or reverse the catastrophic sea level rise predicted with the collapse of the polar ice.

SAI is an extremely controversial idea inspired by the cooling effects that tend to follow large volcanic eruptions. These natural events expel large quantities of dust, ash and often sulfur dioxide into the air. The first two create a shadow effect that causes a short-lasting cooling effect for a couple of hours, but sulfur dioxide tends to rise high into the stratosphere, where it combines with water molecules to create acid particles. sulfuric and remains for up to three years, reflecting solar radiation and causing a long-lasting surface cooling effect.

So the idea behind SAI is to load high-altitude aircraft with sulfur dioxide and fly around spraying it into the high-altitude atmosphere, mimicking the cooling effect of a volcano. So far, so good. Mind you, the way sulfuric acid eventually leaves the atmosphere is by combining into larger and larger droplets that eventually get heavy enough to fall to earth in the form of acid rain, which, as you can imagine, isn’t great for life of plants, fish or animals. And all sulfur oxides are bad to breathe, damage the lungs, and cause asthma and bronchitis if inhaled regularly.

To date, most of the SAI research and modeling has focused on spreading these aerosol deployments around the world. But there is a growing number of scientists who are starting to consider doing this only at the north and south poles. The Arctic and Antarctic are feeling the effects of climate change much worse than the rest of the world at this stage; they are warming many times faster than the global average, causing colossal ice structures to collapse and melt. Each climate model determines the consequent rise in sea level, which will have catastrophic effects around the world.

To state the obvious, no scientist wants to fill the air with sulfur, soak the last remaining polar bears and penguins in acid rain, or give carbon emitters excuses for not cleaning up their behavior. But facing our current trajectory, on which summer sea ice in the Arctic will disappear by around 2050 or earlier, humanity is between a rock and a hard place. All options need to be on the table, evaluated and to some extent ready to go early enough to make a difference.

So the research on SAI is progressing rapidly and focusing it at the poles – an approach called subpolar deployment – could provide better yields at significantly lower costs and acid rain than a global model. Previous research has indicated that spring and early summer are probably the most effective season to do this, and that just doing it at one pole could have asymmetrical effects on the global climate, so it’s probably prudent to target both, with a fleet. of planes traveling with the seasons.

A new study by a fairly broad range of contributors delves into what an SAI bipolar program aimed at “refreezing” the Arctic and Antarctic, how much it will cost, and where the gaps in equipment and technology might be.

The study proposes a nominal north and south pole cooling target of 2 ° C (3.6 ° F), noting that Arctic temperatures have already risen by more than 3 ° C (5.4 ° F) in the past 50 years. He proposes that the aerosol injections be made at the 60th parallel, roughly at the latitudes of Oslo, Helsinki, Homer, Alaska and Magadan, in Siberia in the northern hemisphere, and at the height of the southern tip of Patagonia in the southern hemisphere. At these latitudes, it is possible to do the job more economically, as the troposphere is at a lower altitude and your plane doesn’t have to fly that high. This study chooses an altitude of 13 km (42,600 feet). The released particles would have moved slowly towards the poles, concentrating their effects.

To achieve a 2 ° C result, the plan would inject 6.7 teragrams (6.7 billion kg / 14.8 billion lbs) of sulfur dioxide per year into each pole, requiring a staggering 13.4 teragrams. (29.5 billion pounds) of material per year.

No current aircraft can be repurposed for atmospheric injection activity, so the team specified a “SAIL-43K” design for the job.

Institute of Physics

The study goes on to look into the logistics, finding that existing planes can’t carry enough payload high enough to get the job done. The closest we currently have are military air-to-air refueling aircraft, but these cannot reach target altitudes without significantly reducing their payloads. The McDonnell Douglas KC-10 Extender, for example, could climb into the spray zone carrying around 128,801 pounds (58,400 kg) of payload, but that’s only 22% of the payload it’s designed to carry, so you’d be carrying a lot of weight. in excess on each flight.

Instead, the study proposes a purpose-built stratospray called SAIL-43K, a downgraded version of an aircraft previously specified to fly higher SAI missions closer to the equator. This machine would carry 167,971 pounds (76,190 kg) of payload per mission, but its takeoff weight would be approximately 77,000 pounds (35,000 kg) lighter than the KC-10.

To achieve the cooling target, this project would need 125 purpose-built SAIL-43Ks, which perform a total of 1,458 missions per day during the four-month injection period to each pole. These planes took off, went up for 30 minutes, unloaded the entire cargo of sulfur dioxide within two minutes, then came back down for the next 30 minutes and spent the next hour loading again and refueling for the next mission.

In the Northern Hemisphere there are many airports suitable for this type of operation; practically the entire 60th parallel falls to the ground. In the south, things get a little more complicated as there are really only a few airports in southern Patagonia with proper runways. These are found in latitudes closer to 54 °, but the team calculates that they will get better results simply by dumping sulfur dioxide at that latitude than flying about 490 nautical miles south to reach 60 °.

These airports would need to be upgraded to handle a total of 110 operations per hour, or slightly more than the current busiest airport in the world – this will be a huge undertaking in the Southern Hemisphere, since there are so few airports to start with. in Patagonia. This massive infrastructure work would likely take the time needed to develop and manufacture 125 aircraft, some 15 years after making the decision to push the plan forward. This, in itself, is hardly a quick or complicated part of the process and would require some degree of global agreement on a plan that would disproportionately affect people living in the latitudes in question.

In terms of money, the “relatively low cost” of this project would be around $ 11 billion a year ($ 2022), the team says. That might sound like a lot, but it’s about one-third the price of a global ISC effort with the same cooling goal, and the researchers note that “compared to other possible strategies with which to combat the impacts or causes of climate change, SAI remains extraordinarily little. costly”.

Although calibrated to lower polar temperatures by 2 ° C and to begin refreezing sea ice at the poles, this project will have a number of unwanted side effects. The researchers note that sulfur compounds added to the stratosphere can impact ozone concentrations through a number of different effects and can therefore slow or reverse the recovery of the Antarctic ozone hole. He notes that the effects of sulfur dioxide teragrams and associated acid rain deposits are risky for both humans and the ecosystem in general, and require much more research. And stratospheric warming is also expected.

Furthermore, the planes themselves can only operate by burning jet fuel, using today’s technologies. This annoying fact, in addition to the emissions involved in building all the necessary infrastructure on the ground, in addition to the emissions involved in preparing the sulfur dioxide, mean that a polar ISC program would have its own rather heavy carbon footprint, even if this would only represent. a “marginal” increase in overall emissions from the aeronautics sector.

However, the researchers conclude that ‘although it has not yet been established that the physical or social impacts of any SAI program would prove to be net positive, it seems clear that a program focusing on substantial cooling of the world’s polar and subpolar regions would be logistically possible. halt and likely reverse the melting of sea ice, land ice and permafrost in the most vulnerable regions of the Earth’s cryosphere. This in turn would substantially slow global sea level rise. ”

So, short answer: yes, we can refreeze the poles, minimizing the risk to most of humanity and agriculture. But we would need the whole world to agree that sea level rise is a worse outcome than the effects of a massive SAI program, especially for the estimated 1% of the population living in areas where the effects will be concentrated.

“There is widespread and sensible trepidation about using aerosols to cool the planet,” said Wake Smith, lead author of the new study, in a news release. “But if the risk / benefit equation were to pay off, it would be at the poles. While this could be in a rapidly warming world, stratospheric aerosol injections simply treat a symptom of climate change but not the underlying disease. Aspirin. , not penicillin. It is not a substitute for decarbonisation. ”

The study is open to access in the journal Environmental Research Communications.

Source: Institute of Physics via Phys.org

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