Challenges to the CO2 Global Warming Hypothesis: (9) Rotation of the Earth’s Core as the Source of Global Warming

Yet another challenge to the CO₂ global warming hypothesis, but one radically different from all the other challenges I’ve discussed in this series, hypothesizes that global warming or cooling result entirely from the slight speeding up or slowing down of the earth’s rotating inner core.

Linking the earth’s rotation to its surface temperature is not a new idea and has been discussed by several geophysicists over the last 50 years. What is new is the recent (2023) discovery that changes in global temperature follow changes in the earth’s rotation rate that in turn follow changes in the rotation rate of the inner core, both with a time delay. This discovery underlies the postulate that the earth’s temperature is regulated by rotational variations of the inner core, not by CO₂.

The history and recent developments of the rotational hypothesis have been summarized in a recent paper by Australian Richard Mackey. The apparently simplistic hypothesis, which is certain to raise scientific eyebrows, does, however, meet the requirements for its scientific validation or rejection: it makes a prediction that can be tested against observation.

As Mackey explains, the prediction is that our current bout of global warming will come to an end in 2025, when global cooling will begin.

The prediction is based on the geophysical findings that shifts in the earth’s temperature appear to occur about eight years after the planet’s rotation rate changes, and the earth’s rotation rate changes eight years after the inner core’s rotation rate does. Because the inner core’s rotation rate began to slow around 2009, cooling should set in around 16 years later in 2025, according to the rotational hypothesis.

As illustrated in the figure below, the partly solid inner core is surrounded by the liquid metal outer core; the outer core is enveloped by the thick solid mantle, which underlies the thin crust on which we live. Convection in the outer core generates an electromagnetic field. The resulting electromagnetic torque on the inner core, together with gravitational coupling between the inner core and mantle, drive rotational variations in the inner core.

Although all layers rotate with the whole earth, the outer and inner cores also oscillate back and forth. Variations in the inner core rotation rate appear to be correlated with changes in the earth’s electromagnetic field mentioned above, changes that are in phase with variations in the global mean temperature.

Only recently was it found that the inner core rotates at a different speed than the outer core and mantle, with decadal fluctuations superimposed on the irregular rotation. The rotational hypothesis links these decadal fluctuations of the inner core to global warming and cooling: as the core rotates faster, the earth warms and as it puts the brakes on, the earth cools.

The first apparent evidence for the rotational hypothesis was reported in a 1976 research paper by geophysicists Kurt Lambeck and Amy Cazenave, who argued that global cooling in the 1960s and early 1970s arose from a slowing of the earth’s rotation during the 1950s.

At that time, the role of inner-core rotation was unknown. Nevertheless, the authors went on to predict that a period of global warming would commence in the 1980s, following a 1972 switch in rotation rate from deceleration to acceleration. Their prediction was based on a time lag of 10 to 15 years between changes in the earth’s rotational speed and surface temperature, rather than the 16 years established recently.

Other researchers had proposed a total time lag of only eight years. The next figure compares their estimates of rotation rate (green line) and surface temperature (red line) from 1880 to 2002, clearly showing the temperature lag, at least since 1900. (The black and blue lines should be ignored).

A minimum lag of eight years and a maximum of 16 years means that global warming should have begun at anytime between 1980 and 1988, according to the rotational hypothesis. In fact, the current warming stretch started in the late 1970s, so the hypothesis is on weak ground.

Another weakness is whether the hypothesis can account for all of modern warming. Mackey argues that it can, based on known shortcomings in the various global temperature datasets with which predictions of the rotational hypothesis are compared. But those shortcomings mean merely that there are large uncertainties associated with any comparison, and that a role for CO₂ can’t be definitely ruled out.

A moment of truth for the rotational hypothesis will come in 2025 when, it predicts, the planet will start to cool. However, if that indeed happens, rotational fluctuations of the earth’s inner core won’t be the only possible explanation. As I’ve discussed in a previous post, a potential drop in the sun’s output, known as a grand solar minimum, could also initiate a cold spell around that time.

Next: Estimates of Economic Losses from El Niños Are Farfetched