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Climate Change

Geoengineering: Cool roofs

First in a series about the coming age of machines that consume carbon and emit rainbows.

SL Staff A

• 3 min read
Geoengineering: Cool roofs
What could possibly go wrong....

In 1959 Thomas Austin, an English settler and farmer living in Victoria, Australia, released 24 imported wild rabbits on his property. Austin wanted to replicate some of the feel of England and thought releasing a few rabbits would help. He was quoted at the time saying: “The introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting.”

What ensued was an environmental disaster. Lacking natural predators and having a near-perfect environment of mild winters and abundant vegetation, the rabbits rapidly multiplied, causing severe environmental and agricultural damage. Once started, this proliferation proved impossible to stop despite prodigious efforts, including at one point building a "rabbit proof" fence across the whole country.1 2 In many other similar cases, humans have tried to change the environment for our benefit or to solve a problem: for example, Cane toads (AUS), Kudzu (USA), and Asian Carp (USA). The result in each case was depredation of  the environment. Clearly, the lesson here is that we are not good at "fixing" nature.

For the purposes of this article, we will define geoengineering as the intentional modification of Earth’s environment to mitigate climate change.

As of 2018, the investments being made in geoengineering were estimated to be less than $5 million, but have grown quickly and substantially.3 Bill Gates, Jeff Bezos, and other wealthy individuals are actively seeking investment opportunities in this area.

McKinsey estimates that geoengineering investments could reach $1.2 trillion by 2050.4

With all this investment ramping up, it is only a matter of what and when rather than if we are going to have more geoengineering projects appearing in the next few years. 

Solar Radiation Management (SRM) is one category of geoengineering focused on technologies that reflect the sun’s energy back into space. The measurement of the reflected energy is called albedo, which is expressed as the percentage of the sun's energy that is reflected back into space. Higher albedo means more energy reflected into space ... and reduced global warming. Some examples of SRM technologies include: spraying reflective particles into the atmosphere, brightening clouds, cool roofs, and deploying solar umbrellas.5

Let's look at one of these technologies, the one with the least chance of unintended consequences.

Cool roofs is an initiative that doesn't require inventing new and complex technologies.6 The idea is to increase the reflectivity of surfaces, such as roofs, roadways, and other flat surfaces in urban settings.

A white roof reflects about 80% of solar energy (albedo = .8), while dark roofs reflect only 20% (albedo = .2). This technology is most effective in reducing "urban heat islands" (UHI), a phenomenon wherein urban areas experience higher temperatures than surrounding rural areas. We have all experienced summer days that are hotter downtown than in a park. Urban temperatures can be 1 - 7º C warmer than nearby rural areas, especially on warm calm days. Lower temperatures in the city result in fewer heat-related illnesses, reduced AC demand, and reduced energy usage on hot days.

As we said, unlike most geoengineering schemes, cool roof initiatives have a relatively low risk of unintended consequences, other than some local weather changes in the form of reduced cloud cover and precipitation. They also have limited impact on global heating since urban areas only cover 1-3% of the earth's land area. As a geoengineering initiative this one appears to be in the "go for it" category.

A big concern with the whole area of geoengineering is the lack of oversight. Most of the funding for these technologies is private investment, which comes with an expectation of profit to be made. This drives a "go fast" ethos that puts negative pressure on thoughtful testing and careful rollouts. Couple that with no entity officially considering the global implications of such technologies, and you get a situation in which what is good for one country may hurt another country. Today, nothing stops a nation, state, or wealthy individual from unilaterally implementing any of these new geoengineering ideas.

We may very well need some of these new geoengineering technologies in the near future. Coming up with a way to implement them safely will be a more complicated problem to solve.

But, after all, what harm could come from releasing a few rabbits?

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Reading

  1. Pilkington, Doris. Follow the Rabbit-Proof Fence. University of Queensland Press, 1996.

  2. “State Barrier Fence Overview.” Text. Accessed January 22, 2025. https://www.agric.wa.gov.au/invasive-species/state-barrier-fence-overview.

  3. “Funding for Solar Geoengineering from 2008 to 2018,” November 13, 2018. https://geoengineering.environment.harvard.edu/blog/funding-solar-geoengineering.

  4. “Carbon Removals: How to Scale a New Gigaton Industry | McKinsey.” Accessed January 9, 2025. https://www.mckinsey.com/capabilities/sustainability/our-insights/carbon-removals-how-to-scale-a-new-gigaton-industry?utm_source=chatgpt.com.

  5. Data, My NASA. “Albedo Values | My NASA Data.” Basic page. My NASA Data, November 18, 2019. https://mynasadata.larc.nasa.gov/basic-page/albedo-values.

  6. Energy.gov. “Cool Roofs.” Accessed January 28, 2025. https://www.energy.gov/energysaver/cool-roofs.

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