Proposed plan to dim the sun: is it sci-fi or solar geoengineering?

To understand solar energy, you need to know about solar irradiance. Solar irradiance is the amount of light energy within a certain area. The more irradiance there is, the more energy solar panels can produce.

Solar radiation is a term for the sun's rays. It is different from solar irradiance, which is a measure of the amount of sunlight that falls onto your solar array at any given time. Solar irradiance technically measures the wavelength of light.

According to a new study, solar irradiance has been decreasing in many locations. The main drivers of this decrease are pollution from forest fires and car exhaust fumes. We will talk about why this is, what it means, and what a proposed plan for deliberately dimming the earth’s sunlight might mean for the future of solar power.

Key takeaways

• The amount of sun energy that reaches a certain point has decreased over time because of pollution.
• Aerosols are tiny particles that float in the air. They can reflect sunlight or block it from reaching the Earth.
• There is a proposal to spray sulfur dioxide into the atmosphere to cool the planet and stop global warming.
• There are a lot of things that can reduce the ability for solar panels to absorb sunlight, like pollution and the potential of geoengineering.

What affects solar irradiance?

Solar irradiance is changed by particles in the atmosphere. This includes salt from the ocean, water droplets from clouds, and black carbon from fossil fuel plants.

It is complicated to understand how climate change works. Studying how particles interact with the atmosphere is one part of understanding climate change. Another part is understanding albedo. Albedo refers to how surfaces on Earth reflect sunlight back into space.

Aerosols can change the way sunlight reflects off of different surfaces. In general, lighter surfaces, like ice caps, reflect more sunlight back into space and this helps to cool the planet. But dark surfaces, like the deep ocean, absorb more heat.

Believe it or not, black carbon and pollution from things like coal mine exhaust and sulfur dioxide following a volcano eruption have a slight cooling effect. The dark aerosols block the sunlight from reaching the earth, as seen with the eruption of Mt. Pinatubo - the sulfur dioxide that was emitted cooled the entire earth due to the sheer amount of aerosols.

So, can black carbon actually cool the planet?

Now this is where it gets more confusing. One of the issues with pollution, like coal exhaust, is that it makes the earth warmer. Pollution aerosols reflect sunlight back into the atmosphere, but the sunlight that does reach the earth is absorbed by the particles - similar to how CO2 absorbs heat - and makes the earth warmer.

However, overall, aerosols are believed to have a stronger cooling effect on the planet than their warming effect. For example, in 2020 California's forest fires actually cooled down the entire United States for a few days.

The pollution from the burned trees (and the carbon that was emitted from the burning) stays within the atmosphere. But on top of that, the trees no longer exist, so they can’t absorb the excess CO2.

So yes, aerosols can cool the planet, and there are proposed ideas to use this concept as a way to mitigate certain effects of climate change - more on that later.

What does this mean for solar?

Solar irradiance has decreased by about 7-10% in the United States’ western states, Australia, and India over the last 10 years. In India, pollution was the main cause of this, while smoke from forest fires dimmed the sun in the United States and Australia.

There are not many studies that show how pollution affects solar panel output. However, it is reasonable to believe that with less sunlight reaching the earth's surface, solar panels will perform at less than their peak capacity.

Interestingly, there are studies that show the potential effect of solar geoengineering on solar performance.

What is solar geoengineering?

Solar geoengineering is a way to deliberately change the earth's climate in order to reduce the harms of climate change. There are a few proposed ways to do this, but one of the most concerning is the idea of spraying aerosols into the atmosphere. These aerosols would be like pollution aerosols, and would be added to the atmosphere on purpose.

Solar panels might not work as well if the Earth gets too polluted. This is because pollution would cause the Earth to get colder, and this would also mean that the sun would be less bright. This could make it harder for solar panels to generate electricity. However, it's still important to use solar power because it creates less pollution than traditional power plants.

Other issues with solar geoengineering

There are a few reasons why this technology is not ready to be used right now. First, it is a new technology and typically comes with a lot of issues. Second, we would need to release 50 million metric tons of aerosols into the air every year to block the sun, and we don't have the technology to do that yet. Third, studies show that this technology could have some negative consequences, like reducing the ozone layer or changing rainfall patterns around the world.

What’s next for solar?

There is no neat tie-up to end this, just to say that pollution and geoengineering could reduce solar panel output. But, one can argue that pollution will continue to decline if we shift towards renewable energy through solar power, wind power, and the use of EVs.

What’s tough is climate change has been shown to cause more frequent and intense wildfires, which clog up the sky with smoke and reduce the ability for solar panels to absorb energy.

If the world does not act on climate change quickly by reducing fossil fuel use, then solar geoengineering might be a last-ditch effort to stop the planet from heating up more. Solar geoengineering would reduce the ability of one of our main fighting agents against fossil fuel emissions; the sun.

Governments and businesses might use this as an excuse to continue to push away climate action because they will say that we need to do something about the sun getting dimmer. However, if we reduce fossil fuel use globally, then all of these "what if's" will not be a problem.

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