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Study: Solar geoengineering may offset Arctic sea ice loss

According to a study published by Harvard scientists in the November issue of the journal Nature Climate Change, solar geoengineering may be able to offset rapidly disappearing sea ice in the Arctic—great news for polar bears and other inhabitants of planet Earth.

Solar geoengineering, the primary goal of which is to off-set global warming caused by greenhouse gases, involves the reflection of solar energy back into space. This newest model of solar geoengineering uses increased concentrations of aerosols in the stratosphere or low-altitude marine clouds to achieve this effect. Geoengineering has been criticized in the past as having potentially unequal global effects and unforeseen consequences. However, with this new study, the risk is minimized for the maximum gain.

“Our research goes a step beyond the one-size-fits-all approach to explore how careful tailoring of solar geoengineering can reduce possible inequalities and risks,” said co-author David Keith, Gordon McKay Professor of Applied Physics at the Harvard School of Engineering and Applied Sciences (SEAS) and Professor of Public Policy at Harvard Kennedy School, in a statement. “Instead, we can be thoughtful about various tradeoffs to achieve more selective results, such as the trade-off between minimizing global climate changes and minimizing residual changes at the worst-off location.”

The study—developed in collaboration with Douglas G. MacMartin of the California Institute of Technology, Ken Caldeira of the Carnegie Institution for Science, and Ben Kravitz, formerly of Carnegie and now at the Department of Energy—explores the use of solar geoengineering to counter specific losses.

The particular loss in this case is the important Arctic sea ice, which acts as a sort of global air conditioner, reducing the temperature of the oceans naturally. The new model of solar geoengineering could effectively reduce global warming by restoring this natural global cooling process.

“There has been a lot of loose talk about region-specific climate modification. By contrast, our research uses a more systematic approach to understand how geoengineering might be used to limit a specific impact,” Prof. Keith said. “We found that tailored solar geoengineering might limit Arctic sea ice loss with several times less total solar shading than would be needed in a uniform case.”

While both greenhouse gases and aerosols affect the distribution of heat and rain, they change the temperature and precipitation in various ways according to location. Researchers suggest using this knowledge to deflect sunlight both regionally and seasonally to combat this problem.

“These results indicate that varying geoengineering efforts by region and over different periods of time could potentially improve the effectiveness of solar geoengineering and reduce climate impacts in at-risk areas,” said co-author Ken Caldeira, Senior Scientist in the Department of Global Ecology at the Carnegie Institution for Science, in a statement.

Researchers warned that, although their study was conducted using a state-of-the-art model, any intereference in Earth’s climate could have a number of unanticipated outcomes.

“While more work needs to be done, we have a strong model that indicates that solar geoengineering might be used in a far more nuanced manner than the uniform one-size-fits-all implementation that is often assumed,” Mr. Caldeira said. “One might say that one need not think of it as a single global thermostat. This gives us hope that if we ever do need to implement engineered solutions to combat global warming, that we would do so with a bit more confidence and a great ability to test it and control it.”