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What is The Albedo Effect And How Does it Impact Global Warming?

High albedo and low albedo can change global temperatures through feedback loops, but what is the definition of the albedo effect in the first place?
Ecology News
2023-03-23T00:00:00.000Z
en-us

The albedo effect is a phrase often used when discussing the climate crisis, which has several different types including spectral albedo, planetary albedo, and even higher albedo. High albedo and low albedo can change global temperatures through feedback loops, but what is the definition of the albedo effect in the first place?

👉 And how does albedo affect climate change and global warming?  

What is the albedo effect?

Albedo effect, definition

The definition of the albedo effect is the ability of a surface to reflect sunlight. Light-colored surfaces  (high albedo) reflect more sunlight than dark-colored surfaces (low albedo). Albedo can also be known  as surface albedo.

The albedo effect is the reason why the inside of a black car sitting in the sun will feel hotter than that of  a white car – the black car absorbs much of the energy from the sunlight while the white car reflects it.  

How does albedo affect the climate?

The higher the albedo of a surface, or the more light that gets reflected by earth's surface, the cooler the air will be near that surface. The lower the albedo of a surface, the hotter the same air will be.

If you add up the albedo of every surface on earth, you can average out an albedo for the whole globe.  

Over the earth's history, our planet has generally had a stable global climate when having a stable global albedo. However, if either the global climate or the global albedo were to change, it would affect the other. ⚠️ This relationship can become a feedback loop, which we will discuss later.

Each surface of the earth has a unique albedo. Take a moment to think of some high albedo examples (surfaces that reflect a lot of sunlight) and some low albedo examples (surfaces that absorb a lot of  sunlight).  

sunlight

How is the albedo effect measured?

Albedo is measured using remote sensing. A plane or satellite will send light towards the earth's surface and measure how much light returns to the device.  

Albedo is measured on a scale from 0 to 1. 0 is when a surface absorbs all light and reflects none and 1 is when a surface reflects all light and absorbs none.  

The earth's global average albedo is 0.3, which means about 30% of the sunlight is reflected back from the earth's surface back towards space. That means about 70% of the sun's radiation is absorbed by the planet.

What is the albedo of water?

The albedo of water is about 0.06 in the open ocean. But the albedo of sea ice, on the other hand, can vary greatly. Sea ice that has dark ponds tends to have an albedo of 0.1, while sea ice that has white ice or ice sheets can have an albedo of 0.7.

Here are approximate albedos of other surfaces that have been discussed earlier in this article:

• Forest: 0.15

• Grass: 0.25

• Desert sand: 0.4

• Ocean surface ice: 0.6

• Fresh snow: 0.8

• Aged snow: 0.7

water

Albedo effect examples

High albedo effect examples

Good guess! Both ice and snow are examples of high albedo.

Have you ever stepped outside on a sunny day right after it snows? It can feel quite bright out – that's the albedo effect working its magic, as the incident light or electromagnetic radiation, otherwise known as the amount of light falling on a subject – appears brighter than usual after a moment of overcast weather.

The high albedo of snow is reflecting light into your eyes. 🫣 Compare that to a sunny day when there is no snow covering the ground. The grass or pavement has a lower albedo than the snow, as grass and pavement don't reflect nearly as much light into your eyes as the snow does.  This phenomenon of perceived incoming light can also be referred to as incident radiation, as the amount of electromagnetic waves bouncing offer lighter colored subjects such as snow is larger than that of something darker such as grass. In general, light surfaces such as ice and snow are examples of high albedo, as snow-capped areas such as the Arctic circle reflect solar radiation – preventing the sun in a land surface such as the Arctic Circle from absorbing and melting the surrounding snow covered areas.

The north and south poles are both great examples of high albedo as they are massive snowy and icy land masses. They are essential to the stability of earth's climate – in order to maintain global  temperatures, the earth needs large bright surfaces with high albedo.

The sea ice and glaciers that make up the Arctic and the Antarctic make these locations high albedo examples. Other places with sea ice and glaciers also have high albedo.

sunlight

Low albedo effect examples

The open ocean has a low albedo. Also, grass and dirt have lower albedo than snow does.  

As the climate changes due to global warming, you can guess that the sea ice and glaciers that melt will  lower the overall albedo effect of the earth. And with a warmer climate, some precipitation that would have fallen as snow will now fall as rain. Less snow means less snow cover, further lowering earth's albedo.  

What happens if the earth's albedo continues to decrease? First, let's define global warming. 

What about global warming?

What is global warming?

The definition of Global warming is the increase of the earth's temperature over the past several decades that is caused mostly by humans' burning of fossil fuels. Since the start of industrialization,  earth's warming has been correlated with an increase in global fossil fuel use.  

Is global warming the same as climate change?

While “global warming” and “climate change” are sometimes used interchangeably, “global warming”  only refers to the warming of earth's temperature over time.

“Climate change”, on the other hand,  refers to general changes in climate over time. This includes global warming, more frequent and intense extreme weather events (like hurricanes and monsoons), and bizarre weather patterns.  

What is the link between albedo effect and global warming?

Unfortunately, the earth's albedo has been lowering for decades, contributing to global warming. Since the early 1980's, the average albedo of the arctic has reduced by about 1.5% per decade. While that might not seem like much, even slight changes in albedo can have significant effects on global temperatures.  

You may be asking why the albedo has been decreasing over decades. As it turns out, a changing albedo or a change in global temperatures can create a feedback loop between the two.

Albedo effect and global warming feedback loop

If the earth's albedo decreases, it will create warmer climates. Warmer climates melt sea ice and lower the average seasonal snowfall, lowering the earth's albedo. This is precisely a positive feedback loop.

👉 It is challenging to stop global warming since it is causing a decrease in albedo, which will continue to increase global warming.

It is worth noting that the global warming and albedo effect feedback loop can work to cool the earth, too. 🧐

Take a past ice age as an example. As the earth cooled during an ice age, it resulted in more sea ice formation and snowfall, increasing the albedo and limiting the amount of sunlight absorbed by the earth's surface. Since the earth was then absorbing less light than before, global temperatures continued to decrease, eventually causing an ice age.

sunlight and leafs

Why is the albedo effect important?

The albedo effect is an important tool for understanding global warming. While it is only one of many factors contributing to climate change, tracking the earth's albedo over time can give us a sense of how much heat the earth is reflecting or absorbing, informing prediction models for future temperature changes.  

Pointing out the decreasing of global albedo due to global warming can be a useful tool for convincing the public and lawmakers to fight for reducing our society's impact on the environment and the climate.

How do clouds affect albedo?

Clouds themselves have high albedo. If you think about whether the surface of the earth heats up more  when it's sunny or cloudy, you would likely say “sunny.”  

Have you ever been on the beach during a really hot, sunny day and almost burned your feet on the sand? We can conclude that sand on the beach tends to be hotter on a sunny day than on a cloudy day. The same can be said for all surfaces on earth, as more radiation from the sun on surfaces that do not act as a perfect reflector will absorb that heat and increase the temperature of those surfaces – such as sand at the beach.

Of course, some sun radiation still manages to get through the clouds. It's how you can explain you got a sunburn at the beach on a cloudy day.  

And as we've discussed, the albedo effect tells us that some sunlight that reaches the ground will be absorbed and some will reflect back to space.

However, when thick, high clouds are in the air, the clouds stop much of the energy of the reflecting sunlight from returning to the earth's atmosphere. The clouds trap the heat between the earth's surface and the clouds, acting like a blanket, contributing to the greenhouse effect.

Does deforestation affect albedo?

Good question! Forests themselves have low albedos, absorbing a lot of the sunlight. This is not surprising when you consider that plants are experts at capturing the sun's energy.

Research suggests that in tropical areas, forests do a great job at offsetting their albedo with evaporation cooling the atmosphere, thereby increasing rainfall that cools the earth and boosts cloud albedo.  

👉 Deforestation increases surface albedo but does not make up for the loss of evaporative cooling or lower cloud albedo. (Not to mention the emitted carbon deforestation causes.)

So is the albedo effect good or bad?

The albedo effect itself cannot be declared as good or bad, just like how we cannot say greenhouse gases themselves are good or bad. Without the albedo effect, our climate would not be able to support life on earth.  

The albedo effect works best for all life on earth and the stability of climate when the albedo effect itself is stable. The albedo effect rising or decreasing significantly can cause drastic changes in global  temperatures.  

What happens if the earth's albedo increases or decreases?

If global albedo increases, it will improve the stability of the earth's temperature. If albedo increases too much, it will contribute to a significant cooling of the earth. Both scenarios are unlikely due to the current trend of global warming and the albedo effect feedback loop.

👉 If global albedo continues to decrease as it has over the last several decades, the lower albedo will continue to contribute to global warming and the climate crisis.

So what can be done to increase global albedo?

As we've learned, albedo and temperature change can exist in a feedback loop. The best way to reverse the current global albedo decreasing is to fight climate change. If we can stop the earth's global warming, temperatures will stabilize, causing the albedo to stabilize.  

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