When I see reports that Earth’s ice is melting at the rate of x cubic miles or x cubic kilometers per year I have a hard time getting that in perspective.
Then, I find something that is in tons of ice per year and I can relate to tons of ice…….. as in tons of air conditioning.
The Air Conditioning Industry uses “tons” as one way of rating the capacity of air conditioning units. One ton of A/C provides the same cooling as melting one ton of ice in 24 hours.
Before the advent of refrigeration, cooling was done with ice. Millions of tons of ice were harvested from America’s rivers and lakes and ponds and stored in caves and pits and insulated buildings that preserved the ice well up in to the summer. The ice was stored and later distributed to provide some degree of cooling. Harvesting and distributing ice started before the American Revolution. It is not hard to imagine that when refrigeration units first came on the scene everyone’s frame of reference for cooling was some quantity of ice. Today we still use “tons” to describe the size of air conditioning equipment. More technically, we also use BTUs to rate the capacity of air conditioning equipment.
One BTU is the amount of heat required to raise one pound of water one degree F. A ton of air conditioning moves 11,917 BTUs of heat per hour. At that rate, 286,000 BTUs of heat will be moved in 24 hours. If you have a ton of ice at 32 degrees and you add 286,000 BTUs you will have a ton of water at 32 degrees. The 286,000 BTUs is now “stored” as latent heat in the ton of water. This is the effect of one ton of air conditioning.
Today, a four ton A/C unit is commonly installed to cool a 2000 sq. ft. home. It will remove the amount of heat that it would take to melt four tons of ice in 24 hours. The amount of heat it takes to melt four tons of ice is 1,144,000 BTUs. That melting has no time element but the A/C Industry chose the 24 hours time frame as their standard for rating their equipment.
A recent article from NASA states that the Earth lost 4.3 trillion tons of ice from 2003 to 2010. To get this into air conditioning perspective we need to divide 4.3 trillion tons by 7 years to get 614.3 billion tons of ice melting per year. Then we need to divide by 365 days to get 1.68 billion tons of ice melting per day. That is equivalent to 1.68 billion tons of air conditioning. That equals 481.3 trillion BTUs per day.
If we think of the size of our home air conditioners, 481.3 trillion BTUs would require 420 million 4 ton air conditioners. Or if you live in a small apartment with a 1.5 ton unit, it would be 1.1 billion of these smaller air conditioners.
A 4 ton air conditioner has a foot print of about 10 sq. ft. which would allow 4356 units to cover an acre. When we divide 420 million units by 4356 units per acre, we see that this is equal to 96,418 acres of 4 ton air conditioners. At 640 acres per square mile, this is a field of 4 ton air conditioners that is ten miles long by fifteen miles wide. Or one mile wide and a hundred fifty miles long. I live near Texarkana in Arkansas which is on the Texas border. These 420 million 4 ton a/c units would cover a field that extends a half a mile on each side of Interstate 30. That field would extend from the Texas/Arkansas state line all the way past Little Rock.
All those air conditioners running 24/7/365 would equal the cooling power of the rate of melting of Earth’s ice during that 2003 to 2010 time period. In reality, that many a/c condensing units in that close proximity would not function properly as there is no room for the heat to dissipate. This example is to illustrate how many air conditioners it would take to provide the same cooling as the melting ice if all the a/c units were working properly 24 hours a day for 7 years.
This daily ice melt of 1.68 billion tons requires 481.3 trillion BTUs of heat.
481.3 trillion BTUs is equivalent to burning 20 million cords of Oak fire wood every day,
or 3.85 billion gals. of gasoline…..every day,
or 19.3 million tons of coal……….. Which is enough to fill over 150,000 coal car loads which is over a thousand train loads of coal every day.
That much fuel would have to be burned every day to melt 4.3 trillion tons of ice during those 7 years.
The average Coal fired power plant in the U.S. produce approximately 500 Mega- Watts. The energy to melt 1.68 billion tons of ice per day would require the output of 11,755 of these 500 MW power plants. The super efficient John Turk power plant that opened in Fulton AR in 2012 is a 600 MW power plant. It would only require 9,795 plants of this capacity.
So where did all this heat come from that melted the 4.3 trillion tons of ice?
It came from the Sun.
We have ancient sunshine in hydrocarbons that we burn. We have current sunshine in the biomass and carbohydrates that we burn and in the direct incoming solar radiation. We have some geothermal heat on Earth from geological processes, but most of the energy that is heat on Earth has come from the Sun. At the best conditions we have about 1000 watts per square meter of incoming sunshine to the surface of the Earth. This is approximately equal to a 100W light bulb on every sq. ft. We are now reradiating less energy back to space than in the past because of the infrared reflective effect of increasing greenhouse gases. Much of that heat that is being retained is now stored in the latent heat of fusion in the water that was formerly Earth’s ice.
Earth is warming far more than is indicated by our record high air and water temperatures. We don’t need instrumentation or computer models to see the melting ice.
The reference to train car loads of coal is from “Coal Trains” by John McPhee.
