But the idea has also caused controversy. One nation called the concept of reflecting sunlight a “moral hazard” because it might encourage some countries and industries to deprioritize the reduction of carbon emissions. That fear has stifled research. Yet the pressing need for climate change solutions is pushing things forward, per the White House action. CNBC reported last week that “the White House Office of Science and Technology Policy is coordinating a five-year research plan to study ways of modifying the amount of sunlight that reaches the Earth,” and “the idea is getting more urgent attention in the worsening climate crisis.” Read on to find out what solar geoengineering is and how various techniques would work. 1 What Is Solar Geoengineering?
Solar geoengineering is, simply, reflecting sunlight back into space. The aim is to limit or reduce the damage of human-caused climate change on Earth.  The Environmental Defense Fund, the Union of Concerned Scientists, and the Natural Resources Defense Council have released formal statements of support for researching sunlight reflection. 2 How It Would Work
The concept isn’t just a fantasy. In a March 2021 report, the National Academies of Sciences, Engineering, and Medicine unpacked three types of solar geoengineering: stratospheric aerosol injection, marine cloud brightening, and cirrus cloud thinning.

Stratospheric aerosol injection would involve flying aircraft into the stratosphere (10 to 30 miles up) and spraying a fine mist that would hang in the air, reflecting some of the sun’s radiation back into space. One substance used could be sulfur dioxide. Experts point out this could work quickly, taking the edge of extreme weather events, and we’re already doing this and have for decades—clouds of fossil fuel pollution insulate the Earth from some of the sun’s heat. Marine cloud brightening would increase the reflectivity of clouds relatively close to the surface of the ocean with techniques like spraying sea salt crystals into the air. This is limited in its effectiveness—it would only affect a half dozen to a few dozen miles and last only hours to days. Cirrus cloud thinning would reduce the volume of clouds 3.7 to 8.1 miles high, allowing heat to escape from the Earth’s surface. This isn’t technically “solar geoengineering” because it doesn’t involve sunlight reflection but enables thermal release.

3 What’s Been Proposed
According to the White House’s Office of Science and Technology Policy, the five-year research plan will assess climate interventions, including spraying aerosols into the stratosphere to reflect sunlight back into space, and should include goals for research, what’s necessary to analyze the atmosphere, and what impact these kinds of climate interventions may have on Earth. Congress included the research plan in its 2022 budget, which President Biden signed in March.ae0fcc31ae342fd3a1346ebb1f342fcb 4 1965 Idea Now Has A “Cheap” $10 Billion Price Tag

CNBC reported that the concept of sunlight reflection was first presented to President Lyndon B. Johnson in the 1965 report Restoring the Quality of Our Environment. Back then, the cost of spreading particles over the ocean was estimated to cost $100 per square mile. A 1% change in the reflectivity of the Earth would cost $500 million per year, which does “not seem excessive,” the report said, “considering the extraordinary economic and human importance of climate.” The current estimate is that it would cost $10 billion per year to cool the Earth by 1 degree Celsius. “But that figure is seen to be remarkably cheap compared to other climate change mitigation initiatives,” CNBC says. 5 The Controversy
Some of the techniques proposed for solar geoengineering have risks. One of the proposed aerosols to spray into the atmosphere, sulfur dioxide, is known to cool the Earth after naturally erupting from volcanoes. But dispersing it widely might compromise the ozone layer and create particulates that, once inhaled, can cause lung damage. In fact, the Union of Concerned Scientists say they oppose the deployment of solar bioengineering at this stage—they simply support further research.  Another issue is that some environmentalists consider sunlight reflection a “moral hazard,” because it’s cheaper and easier than reducing carbon emissions. A planned Harvard study was canceled in 2021 after facing this objection. But some experts say that the effects of climate change, such as extreme weather events, have become so clear that all potential remedies must be pursued.