© J. Dirk Nies, Ph.D.
Wow! I am startled. In February, the National Academy of Sciences, through its Committee on Geoengineering Climate, issued a report titled Climate Intervention— Reflecting Sunlight to Cool Earth. This report considers intentionally altering the reflective properties of our atmosphere on a global scale to combat and counteract the detrimental effects of global warming.
According to the National Academy of Sciences (NAS), “Our planet has entered a period in which its climate is changing more rapidly than ever experienced in recorded human history, primarily caused by the rapid build-up of carbon dioxide (CO2) in the atmosphere from the burning of fossil fuels.” They go on to suggest that “… we have reached a point where the severity of the potential risks from climate change appears to outweigh the potential risks from the moral hazard associated with a suitably designed and governed research program.” The research program the NAS has in mind would include evaluating technologies that reduce the amount of sunlight reaching the surface of the planet.
The Climate Intervention Report received support from the U. S. intelligence community, the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA) and the Department of Energy (DOE), showing the breadth of interest within the government on this subject.
This potential enterprise, which in their words is fraught with “unfamiliar and unquantifiable risks,” deserves scrutiny by Americans from all walks of life.
Here is some background information and geological history to help initiate and facilitate this scrutiny.
The Earth has an energy budget. When outflows of heat and light into space equal incoming solar energy, the Earth’s energy budget is balanced. Any perturbation of the amount of incoming or outgoing energy shifts this equilibrium, causing global temperatures to rise or fall.
Sunlight reflected back to space does not contribute to the Earth’s energy budget. Just as our household budget is not based upon our gross pay, but on our net pay after deductions are withheld, so it is with the Earth’s energy budget: the greater the reflectivity of the Earth, like payroll deductions in our analogy, the less global heating.
Scientists use the term “albedo” to describe the degree of reflectivity of an object or material. Albedo, which is derived from Latin for “whiteness,” is that fraction of incoming radiation that is reflected; expressed as a number between 0 and 1. An albedo of 0 means no light is reflected (the object perfectly absorbs light). An albedo of 1 means complete reflection (the object perfectly reflects light). Freshly fallen snow is highly reflective and has a high albedo of 0.9. The albedo of the open ocean (0.07 – 0.10), forests (0.08 – 0.18) and grasslands (0.25) indicate they all are good absorbers of sunlight. Black paint absorbs almost all light. It has a very low albedo of about 0.04.
Roughly 70 percent of sunlight striking the Earth is absorbed by and heats up the land, rivers, lakes, oceans, clouds and the air. The remaining sunlight (30 percent) is reflected back to space and does not contribute to warming the Earth. This degree of reflectivity translates into an albedo of about 0.3, making the Earth a good absorber of sunlight.
For comparison, the Earth’s nearest celestial neighbor, the Moon, is much darker. Its albedo is 0.12. Our neighboring planet Venus, which is covered by dense clouds that are highly reflective, is much brighter than Earth. It has an albedo of 0.76.
The Earth’s average surface temperature is about 58 degrees F. The Earth is revolving around the Sun in the bitter cold of outer space, so that’s actually pretty warm. By increasing its albedo and making the Earth more reflective, the Earth would retain less of the Sun’s warmth and temperatures would drop worldwide. For example, if the Earth were to become covered with ice and snow, its albedo would rise from 0.3 toward 0.9. More sunlight would bounce back into space without contributing its energy to the planet. This decrease in solar heating would cause the temperature of the planet to plummet to a frigid 40 degrees below 0!
Based upon the geological record, scientists posit that ‘Snowball Earth’ has happened; twice! Ice and snow covered the Earth from the poles to the equator more than 2 billion years ago, and again about 650 million years ago.
Apparently, in both cases, it was carbon dioxide that came to the rescue. Derived from volcanic emissions, CO2 slowly accumulated in the atmosphere to levels hundreds of times higher than they are today. These exceptionally high levels of CO2 increased the greenhouse effect, offsetting and compensating the high albedo of ice and snow. As the atmosphere retained more of the Sun’s energy, the Earth gradually thawed out, revealing dry land and open ocean. Photosynthetic microbes and plants along with other mineral processes withdrew CO2 from the atmosphere little by little, dropping its concentration to levels we are accustomed to. These natural responses prevented the world from overheating, as the snow and ice retreated and the Earth’s albedo reverted back to less reflective, more absorbent levels.
The Committee’s report describes techniques by which humans can intervene in these natural processes and intentionally increase the Earth’s albedo. One procedure is to introduce tens of millions of tons of sulfate aerosols into the stratosphere. Modeling studies have shown that cooling, equivalent in magnitude to counterbalance warming caused by excessive CO2 in the atmosphere, can be achieved by this method. Feasibility studies suggest no major technological innovations are required and results would be attained quickly. Costs are estimated to be a tiny fraction of those associated with weaning the world’s economy off coal, oil and natural gas.
In conclusion, human activities such as the clearing of forests, farming and the building of dams, roads and cities have changed, albeit unintentionally, the albedo of land areas around the globe. This research proposal is different; it is a deliberate and premeditated modification of the Earth’s albedo. In essence, we are mulling over writing a prescription to administer pills to the Earth’s atmosphere, in perpetuity, to reduce its chronic fever brought on by a carbon dioxide overdose. As a society, do we wish to pursue a strategy of injecting tens of millions of tons of hazy pollution (sulfate particles) into the stratosphere to counteract global warming?
The Committee “most strongly recommends any such action be informed by a far more substantive body of scientific research – encompassing climate science and economic, political, ethical, and other dimensions – than is available at present.” This is fine but not sufficient. Intentional climate intervention raises questions that go further than any substantive body of scientific research and technology can answer.
First of all, albedo modification does not address the underlying problem. Once we start increasing the Earth’s albedo, we cannot stop decades later—while CO2 has continued to build up in the atmosphere—without potentially unleashing dire consequences. Will we ever be smart enough to anticipate the ramifications of implementing these technologies? And if we are not, do the benefits still outweigh the unknown risks? Beyond all this, what value do we assign a clear blue sky?
Do not rely solely on experts to solve this problem for you. We need the common sense and the ethical and aesthetic sensibilities of the public to be heard.