The Consequences of Light and Heat

February 28, 2015

Snow in a yard.

Copyright 2015 Kevin P. Mick Photography. All rights reserved.

Objects that are bright or white appear to be so because they reflect the majority of light that strikes them.  As a result, they also reflect heat back into the atmosphere.  The expanse of snow in the above photograph is an example-the brighter areas are in direct sunlight and appear white due to the reflection of the sun’s rays.  The accompanying shadow areas appear darker due to the absorption of the light.

 

Autumn leaves that a laying across a snow bank.

Copyright 2015 Kevin P. Mick Photography. All rights reserved.

Objects that are dark or black do the opposite:  they absorb the light and therefore retain the accompanying heat.  These leftover autumn leaves are much darker than the surrounding snow and therefore will absorb more of the sun’s light and heat.

Autumn leaves melting into the snow bank.

Copyright 2015 Kevin P. Mick Photography. All rights reserved.

As a result of that absorption, the darker and warmer leaves begin to melt down through the snow.

Autumn leaves melting into the snow bank-closer view.

Copyright 2015 Kevin P. Mick Photography. All rights reserved.

This phenomenon is pretty easy to demonstrate in the backyard and, on this scale, does not really create any reason for alarm.  The same cannot be said when the same effect occurs on a global scale.

Dr. Jason Box refers to “dark snow”, which is the particulate pollution that enters the atmosphere and then dissipates across the ice sheets of Greenland.  This matter, called cryoconite,  absorbs light and heat and therefore leads to a much quicker melting of the ice and snow, just as the darker leaves are melting into the snow in the above photographs.  As the cryoconite builds up, there is less area of whiter ice/snow to reflect the sunlight and heat and greater amounts of darker ice/snow to absorb the heat, which, in turn, increases the melting of the ice.  As the ice sheets themselves contract, there is a subsequent increase in the surface area of darker ocean, which absorbs more heat and leads to an overall increase in ocean temperatures.  These factors conspire to cause the loss of ice and glaciers around the world, the warming of oceans, and overall climate change.

It was this loss of glacial ice that led photographer James Balog to found the Extreme Ice Survey.  This project was featured in the PBS Nova program entitled Extreme Ice and was later expanded and released in theatres as Chasing Ice.  (Mr. Balog’s TED Talk is here.)  All of these are well-worth watching as this post and leaves in the backyard are nothing compared to the information and imagery in the documentaries.

Take care.

 

 

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