Table Salt May Offer Geo-Engineering Option for Climate Change

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Geoengineering

Common table salt might prove effective in reflecting sunlight and mitigating rising temperatures leading to climate change. How does this happen?

Planetary Science Institute Senior Scientist Robert M. Nelson will explain the details during a briefing today at the 49th Lunar and Planetary Science Conference in The Woodlands, Texas.

Nelson is lead author on the paper "Laboratory Simulations of Planetary Surfaces: Interpreting Remote Sensing Data in Terrestrial Context" that shows salt could potentially be used to offer immediate temporary relief for global warming by deflecting energy from the Sun, keeping Earth cooler.

Nelson's paper presents laboratory measurements of the photometric properties of particulate materials of high reflectance, showing that table salt (NaCl) is remarkably superior to Aluminum Oxide (Al2O3) as a scatterer of sunlight. Widespread distribution of Aluminum Oxide aerosols in Earth's upper atmosphere has been proposed as a means of solar radiation management to offset the effects of anthropogenic greenhouse gases. However, the high Mohs value (hardness) of Aluminum Oxide raises the prospect of subjecting the population of air-breathing animals to the ravages of silicosis-related diseases. The benign effect on air-breathing organisms of table salt makes it a deserving candidate for further research in studies of solar radiation management.

Observations were made using a goniometric photopolarimeter of novel design located at Mt. San Antonio College in Walnut, California. Nelson led an international team with members from Ukraine, China, and institutions around the United States including Mt. San Antonio College, University of Pittsburgh, UCLA, CSU Los Angeles, The California State Polytechnic University at Pomona and the Cal Tech Jet Propulsion Laboratory.

"We note the serious concerns regarding potential unintended consequences associated with geo-engineering concepts," Nelson said. "We suggest further investigation into the feasibility of initiating pilot programs to consider temporary regional application to mitigate short-term, life-threatening conditions in areas where extreme temperature events are forecast."

This work suggests that if NaCl particles are of appropriate morphology and of small particle size and in the form of dispersed discrete random media, then they will be highly reflective at ultraviolet, blue and visual (UBV) wavelengths and transparent in the infrared. It is suggested that even relatively small quantities of materials (with reflective properties of NaCl) distributed as atmospheric aerosols might reduce insolation at Earth's surface by several watts per meter squared (W/m2), the amount estimated by the Intergovernmental Panel on Climate Change to be the anthropogenic contribution to greenhouse warming.

Global application might be considered for immediate relief during a near-term 'transition period' while society acts to reduce anthropogenic greenhouse gas. This transition period might span several decades.

"While the results of our research are very promising, we are at the beginning of the research and additional work needed to understand the extent to which its hypothesized effect in the atmosphere can actually be realized," said Nelson. "Even if successful, this would be a palliative, not a final solution."

Nelson's research was funded under contract from the Cal Tech Jet Propulsion Laboratory in support of the NASA Cassini mission.

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