The debate rages about global warming and the “greenhouse” effect, thought by most to be primarily the impact of GHG’s or “greenhouse gases” to maintain the temperature of the earth surface. The planet is in a warming trend. Almost all agree on this fact.
The cause regarding this warming however is the source of the debate.
CO2 levels are also increasing. So CO2 is considered by many now clearly the cause of the warming.
Most don’t understand the fundamental basic science and physics of the “greenhouse” effect and why the earth remains warmer than it would be in the absence of an atmosphere and the oceans that moderate the impact of the sun’s energy on the earth’s surface.
Skeptics abound with various other theories regarding other factors that may be impacting surface temperatures, but the impact of agriculture generally and agricultural irrigation in particular is widely overlooked and even when considered is misunderstood; even by the very climate scientists providing the data to model the impact of increasing levels of CO2.
To understand the increased warming, first you must thoroughly understand the fundamental warming effect.
It’s not what you may think.
The most powerful impacting force for maintaining the relative temperature stability of the atmosphere is the phase transformation of water and water vapor. Tremendous amounts of solar energy are daily transformed to latent and later back to sensible heat.
CO2 and the other GHG’s are by far secondary considerations and the alterations of mankind to the hydrological cycle of the earth’s land masses are a far better explanation for the warming than any relatively minor changes in the chemical composition of the atmosphere.
Agricultural irrigation on average adds nearly 12 cubic kilometers of water, in the form of water vapor to the atmosphere each and every day.
And this is just the tip of the agricultural climate impact iceberg.
If 12 cubic kilometers of water, in the form of water vapor doesn’t sound to you like it could possibly have an impact on the global climate, let me break it down a bit for you.
A single cubic kilometer of water contains a billion cubic meters of water.
That’s 500 million cubic meters of water/hour.
Just for agricultural irrigation, worldwide; but the vast majority of this water is diverted to the sky in the Northern Hemisphere.
Now, let’s do some basic physics. Temperature is a measure of the concentration of energy, or the average amount of motion per molecule.
Molecules in rapid motion have a higher temperature than those that are moving more slowly.
Adding heat to a substance makes the molecules move faster, and therefore increases the temperature. There is an exception to this, however.
At a certain temperature, specific to each kind of matter, additional heat will change the substance from a solid to a liquid, or from a liquid to a gas, without any increase in temperature.
In the case of water, adding heat to ice at 0 degrees Celsius produces water at 0 degrees Celsius. The heat is all used in freeing the molecules, and the molecules are not moving any faster as a result.
At 100 degrees Celsius, hot water can be changed into steam. It requires a lot of heat but the steam has the same temperature as the water from which it was formed.
It takes about 80 calories to melt a gram of ice, and about 540 calories to
evaporate or boil a gram of hot water.
We are talking about a tremendous amount of heat (energy).
Since the gram was defined as the mass of a cubic centimeter of water, water must by definition have a density of 1 gram per cubic centimeter. It actually varies a little with changes in temperature, but its density is exactly 1 somewhere around 3 or 4 Celsius degrees above freezing.
Now some quick math: 540 calories per gram or stated in joules per cubic centimeter of water would = 2,262.2 joules of solar energy to convert one cubic centimeter of irrigation water into water vapor.
So in terms of increasing the amount of captured power, and converting the rays of the sun into “heat” and efficiently placing this heat into the very lowest layers of the earth’s atmosphere; just how much of an improvement in the biosphere’s principal heating mechanism has agricultural irrigation made?
I realize this concept is somewhat confusing and have come up with an analogy that may help one better understand the “hypothesis.”
But first let’s get through the math.
How many watts of solar energy are converted to latent heat and stored in the earth’s atmosphere by the evapotranspiration of the water used for agricultural irrigation.
12 cubic kilometers per day. 500 million cubic meters of water per hour.
Since a watt = one joule per second, it is helpful to first establish the volume of water per second.
138,888,888.88888888888888888888889 cubic meters of water per second.
To lend some scale to this tremendous volume of water; only one river on earth moves more water. The quantity of fresh water released by the Amazon to the Atlantic Ocean is enormous: up to 300,000 cubic meters per second in the rainy season.
But only during the rainy season. Humans divert from the sea or pump from underground aquifers more water and redirect it to the sky than the average output of any single river on earth empties into the sea.
Next we figure how much energy it takes to convert this additional water to water vapor. Each gram of water requires approximately 2,262.6 joules of energy to make the phase change from water to water vapor.
There are 1 million cubic centimeters in a cubic meter. Now you’ll see why I saved all the 8’s from the previous calculation. We can simply slide the decimal point six places to the right to calculate the number of cubic centimeters of water per second.
138,888,888,888,888.88888888888888889 to arrive at the number of cubic centimeters of water per second. Next we multiply the energy in joules to vaporize this water.
138,888,888,888,888.88888888888888889×2,262.6 = get ready for this.
314,250,000,000,000,000 watts. 314.25 terawatts.
The small t is for thermal.
Now to put this tremendous volume of heat energy into perspective.
Gretchen C. Daily University of California (Berkeley) Anne H. Ehrlich and Paul R. Ehrlich Stanford University (July 1994)
Over a decade ago world energy use amounted to about 13 terawatts, about 70% of which is being used to support somewhat over a billion people in rich countries and 30% to support more than four billion people in developing countries.
Those figures are somewhat dated, so let’s just round off current global energy production from all nuclear, coal, oil and gas at 15 terawatts.
The increase in “stealth” heat added to the atmosphere by the introduction of water to crops that wouldn’t otherwise be available to them contains roughly 21 times the power that is currently produced by mankind globally.
This isn’t anywhere near the total impact of how agriculture and agricultural irrigation change how the biosphere converts the rays of the sun to heat.
But it does give one an idea of the scale of the issue.
Imagine every nuclear power plant, barrel of oil produced, all the natural gas and propane and the coal mined all burned to create just steam that would be released directly to the atmosphere.
Now multiply that X21
Then you must consider that for days or even weeks afterward this additional water vapor being produced is going to absorb additional infrared energy, further heating the earth’s lower atmosphere and underlying surface; be it land, open seas, snow or ice.
The latent (stealth) heat added to the atmosphere in just one cubic meter of water that has been turned to vapor of the same temperature, holds sufficient energy to melt 7 cubic meters of solid ice.