Are sunsets caused by pollution? Sometimes, it does not seem valid, but it makes people wonder about it.
If you have ever taken a few moments to admire the beauty of a sunset, how such an awe-inspiring phenomenon happens might also have crossed your mind.
Is it something to do with clouds or location, or something more sinister, like pollution? Really, does pollution make sunsets pretty?
A mix of gaseous pollutants in the air may make sunsets visually more appealing, but ultimately, they distract from the true colors of sunsets noticed in the tropics.
What is Atmospheric Pollution?
When dangerous or excessive elements are present in the air we breathe, we say there is atmospheric pollution.
These chemicals, also known as pollutants, are typically the product of human activities, such as:
- Power generation
Moreover, these pollutants can take the form of gases, liquids, or solid particles.
Similarly, air pollution can cause various health issues, including:
- Heart disease
- Respiratory problems
It also has a negative impact on forests, crops, and aquatic ecosystems.
And of course, all these elements can contribute to climate change by altering the Earth’s energy balance and raising greenhouse gas concentrations in the atmosphere.
But does this have anything to do with sunsets? Are colorful sunsets caused by pollution?
The Relationship Between Pollution and Sunsets
The idea that pollution creates spectacular sunsets has somehow taken hold.
There is a mix of gaseous pollutants, dust, and other solid particulates low down in the atmosphere.
And in certain circumstances, they will create a colored glow some would find appealing.
However, these pollutants play no role in creating vivid color.
Instead of causing or enhancing a sunset, air pollution mutes it as it interferes with the production of the brightest reds and orange to produce softer shades of yellow and pinks instead.
Fact: As a result of seasonal changes, the times at which the sun rises and sets are never the same twice.
Pollution and the Colors of a Sunset
In the US, the EPA has already identified the major air pollutants, including:
- Carbon dioxide
- Nitrogen oxides
- Particulate matter
Seasonal pollutants, such as pollen and dust, come and go, but the ones mentioned above are constant in the atmosphere.
They are a byproduct of mass transportation and industry and a risk to human health.
In a clean atmosphere we see more of the reds, because the red wavelength is the longest.
Other wavelengths, such as blue, are shorter and get scattered before they reach us.
Understanding the Rayleigh Scattering Effect
This scattering of light is named after its discoverer, Rayleigh. Rayleigh scattering is described as selective and is the reason the sky is blue.
When the atmosphere is polluted, the light hits each particle and undergoes the same splitting effect.
These wavelengths bounce off the irregular surfaces to be dispersed throughout the atmosphere in all directions.
The smaller the particles, the more instances of Rayleigh scattering there are.
Fact: The sun travels at a different rate across the sky each day, which results in varying times for sunset and sunrise.
How Pollution Can Enhance or Detract from the Beauty of a Sunset ?
Although they produce aesthetically pleasing color effects at dawn and sunset, when the sun is low, airborne pollutants reduce the intensity of light.
The amount that can reach the ground is reduced.
It also has to travel further, forcing it to pass through the atmosphere when it is at its thickest and most contaminated.
The abundance of particles, gases and water vapor reduces the brightness of the light.
Sunsets in a Cleaner Atmosphere
In a clean atmosphere with little or no pollution, the colors have intense vividness, especially the reds since the blues being shorter are filtered out and scattered.
With the absence of the shorter wavelength light, blue, green, and purple, it is the longer wavelength colors that reach the human eye.
These are the orange, pink, and red colors now typical of brilliant urban sunsets compared to the deep orange, crimson and red of a natural desert sunset.
Change of Height and Sunsets
The real beauty of sunsets can be observed from a plane. Taking off on a hazy evening the sunset colors, pretty as they are, are diffused and muted tones.
The colors grow in purity and intensity as the plane gains altitude and passes through and beyond the layer of air pollutants.
Sunlight Interacting with the Atmosphere and Sunsets
There are three ways sunlight interacts with the atmosphere, like:
- By hitting the surface
- By being absorbed (transmission)
- By being reflected
How much interaction there is depends on how much sunlight is and the condition of the air it meets.
The colors we see and those we do not, such as radio, infrared, X-ray, ultraviolet and gamma rays, are produced by the light splitting into wavelengths.
We can observe this effect by passing light through a prism.
As light meets the internal structure of the prism, it is slowed down at different rates until it bends, splits into wavelengths and is forced out of the white light as color.
An Important Consideration
Our planet’s atmosphere is multi-layered.
Besides the two gases oxygen (21%) and nitrogen (78%) needed for life, there is a layer of ozone that absorbs ultraviolet solar radiation (sunlight) and retains heat.
Only solar radiation not scattered or absorbed by carbon particles reaches the surface.
Fact: Cape Gisborne is a cape on the north island of New Zealand, in the district of Gisborne, which is the first place on Earth to see the sun rise each morning.
Pollution Affecting the Scattering of Light
Within the atmosphere small solid and liquid particles called aerosols hang suspended.
- Soot and ash
Many of these particles are the products of gaseous chemical reactions from fumes produced by transportation, agriculture and industry, mainly sulfates, nitrates and VOCs (volatile organic compounds).
In locations with fewer aerosols, almost all the light reaches the eye.
We perceive all the colors vividly as all the wavelengths make it to the ground unhindered.
Aerosols Affecting Sunsets
It is important to understand that the greater the mass of aerosols in the air, the less light there is available to reach the eye.
Instead, as it hits the surface of each suspended particle, the light is scattered randomly in all directions.
The effect subdues color and distorts form and clarity creating a haze that obscures details and contains pockets of poor visibility so that some objects seem to disappear completely.
Therefore, you are actually going to find sunsets a bit subdued because of pollution.
Other Factors that Affect the Beauty of a Sunset
Many different factors can actually go into affecting the beauty of a sunset.
- Geographic location
- Weather patterns
- The effect of weather
The Effects of Water Vapor on Sunset
An unpolluted sunset needs the right amount of water vapor for sunlight to pass through and bounce off so the most vivid happen in the tropics.
At the equator, the light has less distance to travel and is less likely to be scattered.
They also happen in deserts, where the atmosphere is super clean. Sunsets cannot happen when there is too much water vapor.
The suspended aerosols fall with the rain, scattering the little light that does get through. This can happen seasonally or daily depending on location and time of the year.
The Speed of Light at Different Times
At sunrise or sunset, with a lower sun, light travels for longer through the atmosphere.
More violet and blue light are scattered out and multiple scattering occurs. A process with near-infinite instances of scattering.
Where pollutants are common, the aerosols become compressed and trapped over cities or industries.
Haze and smog are common, scattering and diffusing all the wavelengths at differing altitudes.
Low wavelengths are lost and it is the resulting red hues of the sunsets that are admired as something speculator.
Fact: The sky becomes less blue as the sun sets, as the light's wavelengths start out green, then go through yellow, orange, and red.
Takeaway: are sunsets caused by pollution
Are sunsets caused by pollution? Air pollution can scatter sunlight, resulting in a reddish, orange, or pink sky at sunrise and sunset.
Pollutants in the atmosphere scatter blue and green light but let longer wavelengths like red and orange through, causing this effect.
But, the truth is that more pollutants in the air actually keep you from observing the real colors of sunsets.
You might want to see sunsets from a higher altitude to get a better idea of this effect.