first_img By Paul VoosenMar. 21, 2018 , 12:10 PM Click to view the privacy policy. Required fields are indicated by an asterisk (*) Sign up for our daily newsletter Get more great content like this delivered right to you! Country THE WOODLANDS, TEXAS—​A last-ditch remedy for a climate disaster might be waiting in your kitchen. If efforts to control greenhouse gases fail, finely powdered salt spread through the upper troposphere could hold off the sun’s rays and cool the planet, researchers reported here today at the Lunar and Planetary Science Conference. The approach could be more benign than other schemes for putting a temporary hold on climate change.For several decades, scientists have suggested ways to “geoengineer” the climate. Several proposals call for injecting microscopic particles, called aerosols, into the stratosphere, the quiet region of the atmosphere above the troposphere about 18 kilometers up from the equator. There they reflect sunlight back into space, mimicking the influence of large volcanic eruptions that have temporarily cooled the planet in the past.Such proposals often involve sulfates, particles that form in the stratosphere from sulfur dioxide ejected by volcanoes, or other molecules with high reflectivity, such as diamond dust or alumina (aluminum oxide). But all these approaches have drawbacks, says Robert Nelson, a senior scientist at the Planetary Science Institute who is based in Pasadena, California. Sulfur dioxide, for example, could eat away at the ozone layer or cause acid rain. Scientists have proposed injecting salt into the upper troposphere, above the clouds, as a form of geoengineering.center_img Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe Email A dusting of salt could cool the planet Alumina could be even worse, Nelson says. Although it is extremely reflective, it could embed in the lungs if inhaled and cause chronic disease similar to silicosis. “I was raised in Pittsburgh, [Pennsylvania,] and I remember as a child seeing black lung victims struggling to get down the street.” Still, given the limited amount of alumina that could be required, it’s far from certain such a health risk would be a genuine concern.So Nelson continued to look for other reflective compounds that might be less hazardous to human health. In 2015, he was studying evaporated salts on the surface of other solar system bodies such as the dwarf planet Ceres. He soon realized that simple table salt is more reflective than alumina, while also harmless to humans. Just as important, Nelson believes that salt, when ground into small enough particles of the right shape and dispersed randomly, would not block outgoing infrared heat released by Earth, adding to its cooling effect.Nelson is not the first to consider salt, says Matthew Watson, a volcanologist at the University of Bristol in the United Kingdom. Watson led a geoengineering experiment, called the Stratospheric Particle Injection for Climate Engineering project, that was canceled in 2012. His group briefly considered salt for stratospheric injection, he says, but problems popped up.First, there’s a lot of chlorine in salt, and chlorine can contribute to destroying ozone. That alone could be enough to kill salt as a candidate, Watson says. Few would likely welcome injecting a particle that could reopen the ozone hole. “[This] could be a big problem,” agrees David Keith, an energy and climate scientist focused on geoengineering at Harvard University. Salt is also highly attracted to water, and water is scant enough in the stratosphere that injecting even limited amounts of salt could potentially alter, for example, the formation of the realm’s wispy clouds, to unknown effects.Nelson hopes these concerns could be addressed by injecting salt in the high troposphere, above the clouds but below the stratosphere. He also plans to look more closely at salt’s properties; if he can resolve some of these questions, he’d like to see a test of the particles above a region forecasted to experience life-threatening extreme temperatures. This would test the science while potentially benefiting society in the short term, he says. Such a research effort could only come after thorough engagement with the public, Nelson adds.But like nearly all scientists interested in geoengineering, Nelson stresses that the strategy is no substitute for action to curb carbon emissions. No type of solar radiation management, for example, would prevent rising carbon dioxide from acidifying the oceans. This research should only be done so the world can potentially buy itself some time, Nelson says. “This would be a palliative, not a [long-term] solution.”*Correction, 21 March, 1:50 p.m.: This story was updated to clarify that Nelson seeks to inject in the upper troposphere, not the stratosphere, as previously stated.last_img

A dusting of salt could cool the planet

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