This is the first thing I've seen on global warming that,

Posted on: April 9, 2017 at 08:44:21 CT

as it has been presented to date, it's threat has been greatly overstated, from a classmate who is certainly one of the smarter people I know.


The Milankovitch Cycle

Some of you may have read Al Gore’s 1992 book, Earth in the Balance, or seen his Academy Award winning “documentary”, an Inconvenient Truth. If so, you may recall that the thesis of man-made global warming is built on two pieces of science.

1. The Greenhouse Theory states that the atmosphere surrounding the earth retains heat from the sun from radiating into dead space, and that one of the atmospheric gases that readily admits short wave solar radiation, but reflects long wave heat radiation is CO2.

2. Analysis of ice cores from Antarctica show that CO2 and temperature have tracked with each other over 2 ice ages (in the book) and 6 of them in the movie. Ice ages have occurred about every 100,000 years for the past 650,000 years.

From these two pieces of scientific data, then Senator Gore hypothesized that atmospheric CO2 drove the temperature (cause and effect), and now with man-made (anthropogenic) CO2 gushing into the atmosphere from burning fossil fuels, we are driving the CO2 way beyond the natural cycles in the Ice Age era (200-300 ppm) to unprecedented levels (now about 400 ppm). In the book, Gore charted them to 600 ppm, double the most ever. He makes the connection by asking that if historically, a change of 100 ppm in CO2 drove a 10 degree Centigrade temperature shift, which along with it drove a 400 feet change in sea level, then what will happen when we drive CO2 to 600 ppm and beyond. The IPCC proposed as worst case now of 1,000 ppm by 2100.

Now indeed, if Gore’s correlation is correct, ie. a 100 ppm CO2 change drives a 10 C temperature change, then 300 ppm would drive a 30 C temperature change or 45 degrees F. Now if this were to happen, winter temps would be above freezing, and the summers hitting 140 F. A drastically different planet than the one we know. Now, Gore never actually cited how big the temperature increase would be, he just ask the question and left it to us to gasp at the possibility.
Having read the book and seen the movie, I was skeptical of the basic science behind anthropogenic global warming for three reasons:

1. Even back in the 1990s, CO2 had been driven up to 340 ppm, 40 ppm more than anything in the past 600,000 years. That should have caused a 4 C temperature rise or about 7 F. Instead, we saw a 0.1 C temperature increase. Clearly far less than Gore’s correlation. Some Gore supporters argued that the effect had a time delay measured in decades. OK, that is possible and reasonable, but 20 years later, we still are drifting warmer in fractions of a degree C.

2. Global temperature records generally exist since about 1850. Before that, they have been inferred from tree rings etc. However, the recorded temperatures show a series of about 25 years of temperature increases, followed by 25 years of stable or even declining temps. The CO2 concentrations since mid-1800s have steadily increased, so what caused the steps? Why not a steady temperature increase if driven by CO2? Explanations have been vague, but generally concern other minor temperature drivers such as ocean currents, al Nina cycles, sun spots, dust in the air … too many to model, but that CO2 was driving the steady increase and these other factors just produced short term variations. Ah, perhaps.

3. However, if CO2 drove temperatures, and we also know that warmer oceans release stored CO2, then if CO2 increases temperature, higher temperature releases more CO2, which drives a positive feedback to ever higher temperatures. What then caused the end of warming in the scientific record? Why have we had 6 cycles of ice ages? There must be a stronger effect that ended the ever rising CO2 and temperature cycle. What was it?

Well, I finally found an answer to the last question. Gore’s correlation of CO2 driving temperature for the past 6 ice ages is a fraud! Here is the story.

About a century ago, a Russian mathematician and astronomer, Milutin Milankovitch, correlated 3 of the earth’s orbital variations with the ice age cycles.

1. Orbit – due to gravitational influences of the other planets, the earth’ orbit varies from circular to slightly elliptical. This orbital factor brings the earth closer to the sun for part of the elliptical orbit, and if the large land mass located in the northern hemisphere is then in summer, the earth is heated. This orbital variation has a period of about 413,000 years.

2. Tilt – The earth’s tilt also varies on a 41,000 year cycle, and again if it results in more solar radiation to the northern hemisphere’s large land mass, which absorbs more heat than the oceans which dominate the southern hemisphere, the planet warms.

3. Axial Procession – the earth’s axis also processes in a 26,000 year cycle, with similar effects.
Milankovitch showed mathematically that when these cycles combine for a warmer northern hemisphere, we get interglacial warm periods, and conversely, ice ages when they combine to cool the northern hemisphere. This is the “other factor” that controlled earth’s climate over the past 600,000 years, and the warming cycles drove CO2 concentrations. Gore’s cause, CO2, is actually the effect. He got it backwards. Milankovitch’s work was not translated into English until 1969, was probably not in the text book that Gore studied in the 1960’s which got him focused on CO2 as a hazard, and Milankovitch's work only slowly gathered acceptance in the Western climate circles. You will note that there is no mention of the 600,000 year ice cycles driven by CO2 in the recent IPCC reports.

So, knowing that CO2 did not drive the 6 ice ages experienced by the earth, are we “out of harm’s way” from climate change? Unfortunately, no. But that is the subject of another essay, if anyone is interested.