Polar geoengineering may exacerbate ocean warming

Modelling sulfate aerosol scheme produces ambiguous outcomes. Nick Carne reports.

Geoengineering will do little to reduce ocean temperatures around Greenland, a study finds.

Geoengineering will do little to reduce ocean temperatures around Greenland, a study finds.

Elizabeth M. Ruggiero/Getty Images

As debate continues over the value or otherwise of using stratospheric sulfur injections to offset some of the adverse effects of climate change, the latest research adds weight to the nay side.

In a paper published in the journal Nature Geoscience, researchers from the US National Centre for Atmospheric Research (NCAR) suggest that such a geoengineering approach might trigger a cooling effect by reflecting sunlight away from the Earth but would do little to reduce the problems faced by oceans.

In fact, it might even exacerbate them. Changing oceanic circulation could lead to continued ocean warming, particularly near southern Greenland.

The authors, the NCAR’s John Fasullo, caution, however, that “the impacts of climate geoengineering cannot be assessed with complete confidence at present”.

Managing incoming solar radiation by enhancing the Earth’s reflectivity has been discussed for more than a decade as a potential way to offset the climate warming caused by greenhouse gas emissions, but the concept is controversial because of what some see as possible significant side-effects, including reducing rainfall over land and shifting regional and seasonal temperature patterns.

In their latest work, Fasullo and colleagues analysed simulations of a climate geoengineering scheme that aims to produce a stable climate by strategically injecting sulfate aerosols into the stratosphere at 15 and 30 degrees latitude in both hemispheres.

They found that this would indeed reduce both surface warming and changes in temperature gradients, as well as minimising the adverse impacts on regional temperatures and rainfall levels.

However, hydrological responses over the North Atlantic Ocean would lead to an acceleration of the Atlantic meridional overturning circulation and to continued warming of the deep and polar oceans.

“Our simulations demonstrate the complexity of the coupled climate response to geoengineering and highlight the need for significant advances in our ability to simulate the coupled climate system and the continued refinement of geoengineering strategies as a prerequisite to their successful implementation,” they conclude.

  1. https://www.nature.com/articles/s41561-018-0249-7
  2. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016EF000407
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