The US Academies of Science, Engineering, Medicine, and National Research moved to abandon aggressive geoengineering techniques — known as atmospheric or albedo-modification — in a new report because they are "not ready for wide-scale deployment" and risk severe unintended consequences.

Besides reducing the amount of carbon dioxide released into the atmosphere, scientists study various ways of changing the Earth's physical and chemical constitution in order to absorb less heat energy from the sun. These methods, known broadly as geoengineering, are intended to counteract the effects of climate change.

When Mount Pinatubo in the Philippines erupted in 1991, a mere 20 tons of sulfur dioxide, which entered the atmosphere, cooled global temperatures by 0.3 °C for three years. A similar effort by humans would be a far less expensive way to cool the Earth than reducing carbon emissions, says the report. 

Other harms caused by warming, however, such as ocean acidification would continue. And releasing sulfur dioxide or putting giant mirrors in Earth's orbit to reflect the Sun's rays could have unintended consequences. The report states:

"In the absence of CO2 reductions, albedo-modification activities would need to be sustained indefinitely and at increasingly large scales to offset warming, with severe negative consequences if they were to be terminated. In addition, albedo modification introduces secondary effects on the ozone layer, precipitation patterns, terrestrial and marine ecosystems, and human health, with unknown social, political, and economic outcomes."

A more benign method of geoengineering, according to Oxford University researchers, is the introduction of Negative Emissions Technologies, such as afforestation — planting trees where currently there are none — and biochar — improving soil by burying a layer of dense charcoal.

Bill Chameides, dean of Duke's Nicholas School of the Environment, agreed with the report (five years before it was issued) in his Big Think interview. Chameides argues that plans for humans to control the global climate are premature:


Read more at New Scientist.

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