Reflecting on Albedo

albedo 1[5021]Sunshine on my shoulders makes me happy,
Sunshine in my eyes can make me cry.”
                             ~ John Denver

A day without sunshine is like, you know, night.”
                             ~ Steve Martin

In the face of growing temperature extremes from climate change, Fred Pearce raises a question posed by a recent study, “If dark heat-absorbing surfaces are warming our cities, why not negate the effect by installing white roofs and other light-colored surfaces to reflect back the sun’s rays?”

Well, many places are doing just that. And in addition, others are looking at other ways to mitigate the effects of climate change on urban heat sinks and maybe sequester carbon along the way. Several approaches attempt to deal with albedo, the reflective characteristic of surfaces. Studies are attempting to evaluate the effectiveness of changing the albedo of urban areas through more reflective surfaces, solar panels and use of vegetation.

Currently, urban developments are generally swaths of black roofs, soaking up and storing heat to be radiated back into the environment. Cumulatively, this creates heat islands that amplify ambient heat levels significantly. In addition, the heat sinks prevent nighttime cooling, worsening heat-related health concerns as the climate changes. Switching from dark building surfaces and roofs to lighter colors has a significant effect on the heat buildup in urban areas.

Solar panels can absorb sunshine, mitigating local temperature increases and providing energy. Similarly, vegetation can block and absorb sunshine, also mitigating temperature increases. ‘Green’ roofs and surfaces have the added benefits of removing particulates from the air, generating oxygen and absorbing atmospheric carbon.

According to Kendra Pierre-Louis, “As cities look for ways to mitigate the effects of global warming, urban green spaces are often cited as a potential solution.” They can moderate storm water runoff and improve runoff water quality. Urban soils can also have a role in carbon sequestration. Research “showed that the soil in forest ecosystems was best at absorbing water. But soil on open and developed land — like golf courses and backyard lawns — was better at absorbing carbon … minimizing pavement and keeping green spaces green was an important first step … Backyard soils can lock in more planet-warming carbon emissions than soils found in native grasslands or urban forests like arboretums.”

But it’s not just urban areas where albedo and surface conditions can mitigate some climate change effects. Pearce notes, “farmers could cool rural areas, too, by altering farming methods. Different methods might work in different regions with different farming systems. In Europe, grain fields are almost always plowed soon after harvesting, leaving a dark surface of soil to absorb the sun’s rays throughout the winter. But if the land remained unplowed, the lightly colored stubble left on the fields after harvesting would reflect about 30 percent of sunlight, compared to only 20 percent from a cleared field.”

It has also been suggested, notes Pearce, that crops could be chosen for their ability to reflect sunlight. “For instance, in Europe, a grain like barley, which reflects 23 percent of sunlight, could be replaced by sugar beet, an economically comparable crop, which reflects 26 percent. Sometimes, farmers could simply choose more reflective varieties of their preferred crops.”

Brad Jones sees farming as a way to also sequester carbon in soils, “A new study suggests that the planet’s farmland soil has unrealized carbon trapping potential, and could be used to remove as much carbon from the atmosphere as the transport industry emits.” New technology might include:

  • Monitoring soil health with sensors and drones,
  • Reduced reliance on fossil fuel-burning heavy machinery,
  • The implementation of mulch to protect the soil’s surface,
  • Introducing legume plants into pasture vegetation to increase soil carbon storage, and
  • The practice of agroforestry – planting trees on farmland to fix nitrogen in the soil.

Agroforestry — agriculture incorporating the cultivation and conservation of trees can also help to minimize heat extremes. Twilight Greenaway quotes Mark Kopecky, a soils agronomist at Organic Valley, “trees can keep pastures from overheating during record-breaking heat waves, especially in warm regions such as the South. Partially shaded pastures also allow cows to graze all day rather than at dawn or at dusk.”

As we grapple with the effects of climate change, it becomes obvious that there is no one magic solution, but interrelated actions spanning various aspects of the problems. It is not solely an urban, rural or undeveloped land issue.

It is after all, our shared climate, and we will need to share the solutions as well as the problems.

Additional information:

Twilight Greenaway, The Farm for the Trees, TakePart’s Big Issue, Vol 13, http://www.takepart.com/big-issues

Brad Jones, Farming Has a Huge Impact on the Environment. Enter Carbon Trapping. January 30, 2018, Futurism

Fred Pearce, Urban Heat: Can White Roofs Help Cool World’s Warming Cities? March 7, 2018, Yale Environment 360

Kendra Pierre-Louis, A Secret Superpower, Right in Your Backyard, March 6, 2018, The New York Times

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