Gli scienziati affermano che il ricongelamento dei poli della Terra è sia possibile che notevolmente economico

I poli della Terra si stanno riscaldando molte volte più velocemente della media globale. In effetti, all’inizio di quest’anno sono state segnalate ondate di calore da record sia nell’Artico che nell’Antartico. Lo scioglimento del ghiaccio e il collasso dei ghiacciai alle alte latitudini accelererebbe l’innalzamento del livello del mare in tutto il pianeta. Fortunatamente, sarebbe straordinariamente fattibile ed economico ricongelare i poli riducendo la luce solare in entrata. Questo secondo una nuova ricerca pubblicata il 15 settembre 2022 su IOP Publishing’s Comunicazioni di ricerca ambientale.

Gli scienziati hanno ideato un potenziale futuro programma di geoingegneria in cui getti ad alta quota spruzzano microscopiche particelle di aerosol nell’atmosfera a latitudini di 60 gradi nord e sud, all’incirca Anchorage e la punta meridionale della Patagonia. Se iniettati a 43.000 piedi/13.000 metri (sopra le altitudini di navigazione dell’aereo), questi aerosol andranno lentamente alla deriva verso il polo, ombreggiando leggermente la superficie al di sotto.

L’autore principale Wake Smith osserva: “Ci sono preoccupazioni diffuse e ragionevoli sugli schieramenti di aerosol per raffreddare il pianeta, ma se l’equazione rischio/beneficio darà i suoi frutti, è ai poli”. Smith Docente presso[{” attribute=””>Yale University and a Senior Fellow at the Mossavar-Rahmani Center for Business and Government at Harvard Kennedy School.

Particle injections would be performed seasonally in the long days of the local spring and early summer. Both hemispheres could be serviced by the same fleet of jets, ferrying to the opposite pole with the change of seasons.

A tabular iceberg floating within Paradise Harbour, Antarctica. Credit: IOP Publishing

Pre-existing 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. However, newly designed high-altitude tankers would prove much more efficient. A fleet of roughly 125 such tankers could loft a payload sufficient to cool the regions poleward of 60°N/S by 2°C per year. This would be enough to return them close to their pre-industrial average temperatures. Annual costs are estimated at $11 billion. This is less than one-third the cost of cooling the entire planet by the same 2°C magnitude and just a tiny fraction of the cost of reaching net zero emissions.

“Game-changing though this could be in a rapidly warming world, stratospheric aerosol injections merely treat a symptom of climate change but not the underlying disease. It’s aspirin, not penicillin. It’s not a substitute for decarbonization,” says Smith.

Cooling at the poles would provide direct protection for only a small portion of the planet. However, the mid-latitudes should also experience some temperature reduction. Since less than 1% of the global human population lives in the target deployment zones, a polar deployment would entail much less direct risk to most of humanity than a global program.

“Nonetheless, any intentional turning of the global thermostat would be of common interest to all of humanity and not merely the province of Arctic and Patagonian nations,” adds Smith.

In summary, the current study is just a small and preliminary step towards understanding the costs, benefits, and risks of undertaking climate intervention at high latitudes. It provides further reason to believe that such tools could prove useful both in preserving the cryosphere near the poles and slowing global sea level rise.

Reference: “A subpolar-focused stratospheric aerosol injection deployment scenario” by Wake Smith, Umang Bhattarai, Douglas G MacMartin, Walker Raymond Lee, Daniele Visioni, Ben Kravitz and Christian V Rice, 15 September 2022, Environmental Research Communications.
DOI: 10.1088/2515-7620/ac8cd3