Restoring arctic ice with fake airborne volcanic particles New Scientist

We can make the arctic ice grow by injecting particles into the atmosphere that block sunlight. According to an American research group, this is a feasible and relatively affordable way to refreeze the North and South Poles.

The poles are warming much faster than the rest of the world. The temperature at the South Pole is rising about three times faster than the average on Earth. Almost four times faster at the North Pole.

The melting of snow, ice and glaciers at the poles is causing a rapid rise in sea levels. In addition, white snow and ice surfaces largely reflect sunlight, while a darker surface or the sea absorbs most of the heat from the light. For example, the disappearance of ice accelerates global warming.

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Spraying of sulfur particles

To counteract this catastrophic melting of the Arctic ice, scientists propose sending planes into the sky to spray microscopic particles into the atmosphere. These aerosol particles would reflect some of the sunlight back into space. This creates a modest shadow on the underlying ground or ice surface. As a result, the surface heats up less and the ice gets a chance to grow again.

“To begin with, we would probably use sulfates such as sulfur oxide (SO2)’, emailed climate scientist Wake Smith from the American Yale University. “These are the same particles that Mother Nature blows into the atmosphere via large volcanoes. We therefore know that they cool the planet and there is less chance of unexpected side effects.’

The stratosphere above the polar ice cap

In the researchers’ plan, the aerosols are sprayed into the atmosphere at 60 degrees north latitude and 60 degrees south latitude. It is roughly at the height of the northern city of Anchorage in Alaska and the southern tip of Patagonia in South America. From there, the particles would gradually drift towards the North and South Poles.

For the aerosols to float in the air for months – and not rain down after a few days – they must reach just above the tropopause, in the stratosphere. The tropopause is located at latitude 60 degrees north above about 13 kilometers altitude, so you have to fly that high just to spray the aerosol particles into the stratosphere.

The researchers estimate that a fleet of around 125 modern tankers could spread enough aerosols to cool both polar regions by 2 degrees Celsius per year. It will cost around 11 billion euros per year. That is less than a third of what it would cost to lower the global temperature by two degrees by spraying aerosols into the atmosphere.

Because the particles disappear after a few months, the process should be repeated annually, during the local spring and early summer.

In this scenario, only the polar regions cool. Still, it can have a global effect, partly because it slows sea level rise. Another advantage is that they are sparsely populated areas, which means it poses less risk than a global rollout.

Risks

But spraying particles into the atmosphere is not entirely without risks. Smith: ‘The risks we know are small. There is the possibility of, for example, some more acid rain, slight warming in the stratosphere and a delay in the recovery of the ozone layer. In addition, there may be unknown unknowns, whose risks we cannot yet assess. So decades of research must be done before it can be used.’

Furthermore, Smith emphasizes that it is symptomatic, not a cure. Aerosols are not a substitute for reducing greenhouse gas emissions. That remains the goal. ‘The aerosols would at best be a tool to reduce heat stress in the future.’

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