While admitting that the Milankovich cycle was the real culprit.
A new record of past climate change supposedly provides compelling evidence that CO2 was the big driver of global warming at the end of the ice age.
“At the end of the last ice age, CO2 rose from about 180 parts per million (ppm) in the atmosphere to about 260; and today we’re at 392,” explained lead author Dr Jeremy Shakun in a BBC News interview. “Rising CO2 at the end of the ice age had a huge effect on global climate.”
Dr Shakun’s team constructed a narrative to explain the process:
- This starts with a subtle change in the Earth’s orbit around the Sun known as a Milankovitch “wobble”, which increases the amount of light reaching northern latitudes and triggers the collapse of the hemisphere’s great ice sheets
- This in turn produces vast amounts of fresh water that enter the North Atlantic to upset ocean circulation
- Heat at the equator that would normally be distributed northwards then backs up, raising temperatures in the Southern Hemisphere
- This initiates further changes to atmospheric and ocean circulation, resulting in the Southern Ocean releasing CO2 from its waters
- The rise in CO2 sets in train a global rise in temperature that pulls the whole Earth out of its glaciated state. (“If you believe this last point, you are ready to believe anything,” says analytical chemist Hans Schreuder.)
So let’s look at this. What happened first?
First, came the Milankovitch “wobble.” Then came the rise in CO2.
Saying that the rise in CO2 drove the earth out of the ice age is like saying that someone riding on the roof of a bus is driving the bus.
The end of the last ice age was not triggered by rising CO2 levels, it was triggered by the Milankovich cycle. It nothing to do with humans back then, and it has nothing to do with humans now.
The Milankovich cycle is caused by a natural process known as precession of the equinoxes.
Here’s how I describe equinoctial precession in Not by Fire but by Ice. (p. 169-170)
Equinoctial precession – Pacemaker of the ice ages
(The earth’s) axis of rotation wobbles like a top, tracing a clockwise circle around true north. Called axial precession, it takes about 25,800 years to make the full circle. Precession occurs, say scientists, because the sun and moon exert a gravitational pull on the earth’s equatorial bulge. Rotating objects such as tops and gyroscopes also precess. So does Mars.
To understand this phenomenon, picture the globe spinning around a long stick (the axis of rotation). Tilted away from true north, the top of the stick traces a circle around the North Pole, while the bottom makes an identical trip around Antarctica.
As our axis of rotation moves, it constantly points toward a different star. If the stick were longer, it would paint an imaginary circle on the heavens. The process of painting that circle on the celestial ceiling is called precession of the equinoxes.
This is not a new theory. The Greek philosopher/scientist Hipparchus first discovered precession of the equinoxes in the second century B.C. when he compared his own astronomical measurements to those made by Timocharis some 150 years earlier. But he mistakenly concluded that the stars were moving in a circle through the sky.
Eighteen centuries later, Sir Isaac Newton solved the rest of the riddle. Our orbit around the sun also revolves, said Newton. The orbit itself revolves backwards, or counterclockwise. Precession of the equinoxes, the time it takes to paint that imaginary circle on the heavens, therefore takes about 23,000 years. It’s like waiting for someone on a merry-go-round. You’ll reach them sooner if you walk toward them.
This is deadly important. The equinoctial precession cycle is a killer . . . and it’s about to strike again.
Today when viewed from the northern hemisphere, the stars seem to rotate around Polaris at the end of the handle of the Little Dipper. That’s why it’s called the Pole Star; because the North Pole points toward it. But in 2,000 B.C. the North Pole pointed toward a spot halfway between the Little Dipper and the Big Dipper. In 4,000 B.C. it pointed toward the end of the handle of the Big Dipper. Twelve thousand years from now it will point toward a different star, toward Vega, and in 23,000 years it will point toward Polaris again.
Forget your CO2.
Equinoctial precession is the real pacemaker of the ice ages . . . and it is about to lead us into the next ice age.
See entire BBC article:
Thanks to Hans Schreuder and Winona Campbell for this link