Why does a large fraction of the American public deny the truth of global warming? Well, for one thing, what is out of sight is out of mind. We heat our homes with gas or oil that we do not see. Once in a while, if we look inside the furnace, we’ll marvel at the beauty of the cool blue flame. But we have no sense of how much gas is actually flowing, or how much oil we’re actually consuming. So we, the warmed citizens of this country, can’t appreciate how much of that fossil fuel is actually being burned to CO2 gas and released into the atmosphere.
Likewise, we consume electricity in our homes for lighting, powering appliances, for air conditioning in the summer, and in some cases for space heating instead of gas or oil heating mentioned above. Here too, even more so, we as consumers are fully and effectively shielded from the vast amount of carbon based fuels burned to produce the electricity we use. Almost all electric power in the US is produced from coal and natural gas. Who among us has any sense of the vast tonnage of coal, or the millions of cu. ft. of gas, that are burned (with relatively poor efficiency) to generate that power? Electricity is delivered to us through wires hidden from view inside the walls of our houses, and of course we can’t count the electrons coursing through those wires to our homes as we go about our daily routines.
Third, gasoline- or diesel-fueled transportation effectively conceals any sense of consumption of liquid. We pump an invisible liquid through an opaque hose into an unseen gas tank, that mystical internal storage compartment in our cars, trucks and buses. But we really can’t grasp how much we’re pumping in, or how much it weighs. Gas stations aren’t equipped with auto scales so that we could actually measure the weight of gasoline added by filling up. Further, we have no sense of how much CO2 is actually produced when that weighty liquid is burned to CO2 and released into the atmosphere. So there’s no sense of the CO2 burden we’re imposing on the atmosphere with every fill-up at the gas station. And of course, that CO2 vapor is colorless and odorless, so we don’t sense the final product of our transportation consumption either.
Here’s a simple illustration intended to help us grasp how much CO2 we actually release when driving a car. Suppose your car is representative, and takes about 15 gallons of gasoline to fill up the tank. When you do so, you’ve added about 84 pounds of gasoline liquid (see the first figure, below).
|Weighing a tankful gas in your car on a fulcrum balance.|
When burned in your engine (and after the exhaust passes through the catalytic converter of the car) you’ve produced about 260 pounds of CO2. (You’ve also produced some water vapor, but that’s not significant for our discussion about the greenhouse gas effect.) CO2 can be liquefied by applying extra pressure and cooling it; as a liquid these 260 pounds would measure about 69 gal. If that were kept in an on-board pressurized tank, it would have to be much larger than the gas tank that you filled at the pump.
But in reality, without compression and cooling CO2 is a gas. These 69 gal. of liquid CO2 would actually occupy about 16,400 gal. of gaseous volume, if that volume contained the pure CO2 and no other components of air (see the second figure, further below). But in today’s atmosphere, the distributed concentration of CO2 in the air is about 360 parts per million (ppm), meaning that in 1 million gallons, for example, of air volume, 360 gallons would be CO2 (thus, 360 ppm) and the remainder would be the other components of our atmosphere, such as nitrogen, oxygen and water vapor. So if we now equilibrate the 16,400 gallons of CO2 vapor from burning our tankful of gas into the atmosphere, and considering a cubic volume, this CO2 would be distributed into a cube about 180 feet on a side. For comparison, most mature trees are about 60-80 feet tall (see the second figure); and a building this tall would have 12-18 stories.
|Virtual cube 180 feet on a side showing the volume that would be occupied by liquid CO2, |
by the same amount of pure CO2 gas, and by distributed skunk-odor-linked CO2
produced by burning one tankful of gasoline. A mature tree is shown for comparison.