Climate Change | Environment |

How earth’s albedo effects global warming: can geoengineering help?

Definition

Albedo is the measure of reflectivity of an object. A scientific definition describes albedo as “the fraction of the total incident solar radiation reflected by a planet back to space that is a measure of the planet’s energy balance”. Every object has a different albedo. The objects with higher albedo are cooler in temperature than the objects that have a lower albedo.  It is either measured on a scale of zero to one or as a percentage. An object that has zero albedo reflects zero per cent and absorbs hundred per cent of the radiation it receives. This perfect absorber is known as a black body object. Hypothetically, the opposite is true for a pure white body which is a perfect reflector (such as thick Antarctic ice sheet). It has an albedo of one, reflects hundred per cent and absorbs zero per cent of the radiation it receives. In context of the Earth, solar radiation or solar energy reflected back from the Earth’s surface in the form of short waves is known as the Earth’s albedo and is usually expressed as a percentage.

Over the years, scientists at NASA have studied the albedo of different earth surfaces: vegetation cover, snow cover and glaciers, ocean surfaces and the surface of other water bodies, deserts, and so on. Since 1997, the Clouds and Earth’s Radiant Energy System (CERES) instruments have been measuring the albedo of various surfaces on earth to calculate the earth’s albedo. The snow or ice covered surfaces like polar ice caps and glaciers have an albedo of 0.5 to 0.9 (fifty to ninety per cent sunlight they receives is reflected back) whereas an ocean surface has an albedo of 0.06 (only six per cent of the sunlight it receives is reflected back). A surface with vegetation cover reflects as much as ten to sixty per cent sunlight back. Overall, the earth’s albedo is 0.3. In other words, it reflects thirty per cent of the solar energy it receives.

According to the data collected by CERES instruments aboard the Terra satellite, the earth’s albedo changed between March 1, 2000, and December 31, 2011. “What the results show is that even at global scales, Earth’s albedo fluctuates markedly over short time periods due to natural variations in the climate system,” said Norman Loeb, CERES principal investigator at NASA’s Langley Research Center. Ice cover, cloud cover, and the amount of airborne particles like aerosols from pollution, volcanoes, and dust storms, can change reflectivity on scales from days to years. “We should not get fooled by short-term fluctuations in the data, as a longer record may reverse any short-term trend.”

Many experiments have been conducted to reduce earth’s albedo. High-albedo, white and cool roofing membranes are recognized as a fundamental strategy that dense urban areas can deploy on a large scale, at low cost, to mitigate the urban heat island effect. Three generic white membranes had been monitored within New York City that represented a cross section of the dominant white membrane options for US flat roofs. The results indicated that professionally installed white membranes maintained their temperature control effectively and met the Energy Star Cool Roofing performance standards requiring a three-year aged albedo above 0.50 (Gaffin et al, 2012).

However, many scientists and researchers have views against the reduction of earth’s albedo. “Increasing the albedo of urban and human settlement areas can in turn decrease atmospheric temperature and could potentially offset some of the anticipated temperature increase caused by global warming”, wrote Hashem Akbari, H Damon Matthews and Donny Seto (2012).

Solar Radiation Management Governance Initiative (SRMGI)

SRMGI is an international, NGO-driven project that seeks to expand the global conversation around the governance of SRM geoengineering research. In October 2011 SRMGI partnered with two Indian NGOs and a workshop was convened in Delhi. The two partner NGOs are: The Council on Energy, Environment and Water (CEEW) which is a Delhi-based policy research institute working on global challenges such as sustainable growth and development, through research on energy, environment, and water and the Centre for Study of Science, Technology and Policy (CSTEP) which is a multi-disciplinary policy research organization that seeks to enrich policy-making for a sustainable, secure and inclusive society. In November 2016, CEEW partnered with SRMGI a second time to host a workshop. Both of these workshops involved presentations and discussions on climate change, on the potential impacts of SRM, and the latest research from the sciences and social sciences.

Geoengineering

Geoengineering, also known as climate engineering, refers to the calculated wide-ranging manipulation of environmental processes that affect the Earth’s climate, to curb the effects of global warming. Global warming refers to the increase in the overall temperature of the world, mainly ascribed to augmented greenhouse effect and reduced albedo effect. Greenhouse effect is a natural phenomenon through which the solar radiation is trapped in our atmosphere by greenhouse gases which chiefly include carbon dioxide (CO2), methane, hydroflurocarbon (HFC), nitrous oxide, ozone and water vapour. This greenhouse effect has been heightened by man-made chloroflurocarbon (CFC), excess CO2 produced by human activities, and other pollutants. Geoengineering primarily focuses on either lowering the presence of the CO2 in the air or decreasing the amount of sunlight making it to the earth’s surface.

To reduce the presence of CO2 in the atmosphere, the following plans of action have been suggested by experts in this field:

  1. Planting ‘Artificial Trees’ that are actually machines which absorb CO2 from the air using plastic polymers.
  2. Making oceans a bigger carbon sink than they already are by adding huge amounts of lime to the oceans.
  3. Using and enhancing the ability of trees and plants to absorb CO2.
  4. Using carbon-capture technology while burning large quantities of wood in thermal power plants.
  5. Converting gaseous carbon to charcoal and burying it underground.
  6. Designing a way to convert cattle grazing grounds into carbon sinks.

 

Coming to the ways of increasing the Earth’s albedo following are the suggestions made by geo-engineers:

  1. Firing sulphate aerosols into the stratosphere to reflect sunlight back to space.
  2. Spraying seawater
    Global Warming due to Earth's Albedo

    Earth’s albedo is the measure of the reflectivity of solar radiation received by Earth. The changing pattern of Earth’s albedo over the years has been a cause of concern.

    into the air to increase above-ocean cloud cover.

  3. Painting the world’s roofs white to increase reflectivity.
  4. Floating thousands of tiny mirrors in space between Earth and the sun,

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